COMMENTARY

Good morning (or afternoon depending on when you see this) WHW readers! A quick review of the expectations and results of yesterday’s storm and some additional thoughts. This was a system that for many days was expected as a possibility “around the weekend” with many model forecasts just a handful of days before the event having it as a low pressure system tracking through the Great Lakes and a rain event here, in which the biggest challenge would have been whether or not the warm front was going to pass the entire region before the cold front arrived. It would have been too warm for anything other than rain to be involved in the precipitation shield. But many forecasters knew better that a solution such as that, or any other solution for that matter, that far in advance with recent and ongoing model performance issues was not something that you could look at and have any confidence in whatsoever. Hence, the forecasts (at least mine and probably many others) were written in vague terminology, which should always be used to reflect uncertainty. There is nothing wrong with uncertainty in the scientific process. If not for it, we’d lose our desire to learn and improve. As we got closer to the event, and it become more and more obvious that the track and development of the low center, and precise details around both, would leave the tiniest margin for error for making or breaking our forecasts on it, I can speak for myself and others when I say the challenge become the real deal. One of my colleagues noted how a 1 or 2 degree difference could literally make the difference between an inch of snow and over a half foot of snow, and the 1 or 2 degree difference was not just the temperature at the surface, but the temperature throughout the entire depth of the storm from surface to top of clouds. That one small aspect, before we include all other aspects, went very much into determining a much bigger outcome, as noted by a comment on yesterday’s blog, the final snow numbers. This, not necessarily through any fault of their own, is what the general public is looking at. Joe Public doesn’t really care what my temperature forecast is for 850 millibars, if the wind direction is from direction 20 or 330 (yes it makes a difference), or any of that. Joe Public wants to know how much snow he has to shovel, or plow. And I get that. Unless one is a weather geek, they’re not looking at forecasts and listening to media for discussions of a storm’s dynamics, they just want to know what, when, and how much. I assure you every forecaster out there gave it their all in trying to figure this one out. Some forecasts worked out OK, some did not. Some worked out great in some areas and poorly in others. That’s the nature of what we do, and this was a prime example of that. We saw a lot of good forecasts for nearly every detail of this system, from its evolution and its track, to its precipitation timing and marginal temperature profile, snow being dependent on precipitation intensity in bands we had to try to forecast development of, and intensity of, and worry if these bands would even form enough at all to do what we expected. How ironic that, in many (not all) areas, that the only aspect of the forecast that didn’t work out as well was the ONE that most people were most interested in. Most of them didn’t care that the 1 to 2 1/2 inches of rain forecast before any mixing and changing did indeed occur, and as a result gave our drought yet another gut punch. That’s some good news. Ah, so Joe Public may have any number of reactions. He may be posting on social media this morning that “they got it wrong again! what a great job where you can be wrong and still get paid” (old joke, heard it before), or he may be a snow lover who is just angry that only a slushy inch or two of snow fell when he was expecting 6 and a perfect forecast, or he may be happy because even though he doesn’t mind some December snow, that we didn’t have enough to bring down a hundred more trees in his city putting most people in the dark for a day or longer, and causing more damage. People have their reactions, and that’s fine. But no matter what we expect and how we react, I’d like to remind all of them for a moment to remember what goes into making these predictions, and how easily they can go awry, and how often they don’t compared to how often they do. I say this, not because I think more folks than usual are bent out of shape about the snow aspect of this system, but because it’s important for us to try to understand what goes into doing a job, and I don’t mean just weather forecasting. This can be applied to any position, and a couple that come to mind immediately are first responders, which goes without saying, and utility workers. Yes, it sucks when the power is out for any length of time, but understanding why it may take some time for them to get to the line down the street that was cut by one branch, while there are hundreds and maybe even thousands of others just like that, and that yours can’t always be first, is very important. The set-up for doing these jobs isn’t perfect, and will never be perfect, but people in these do the best they can. The same with weather, really. Forecasting is never going to be something we ever achieve perfection in, but doing the best you can should never be thought of as failure. Aspects of a forecast may fail sometimes, but a strong effort is always a success.

DAYS 1-5 (DECEMBER 6-10)

Low pressure exits via the Canadian Maritime Provinces today, leaving in its wake a blustery and cold day with passing clouds and a remote chance of a few snow flakes or rain drops falling from some of these clouds. With winds still gusty, keep an eye out for loose branches that may still be caught in trees. The damage from yesterday’s storm was not too bad, but older trees still saw some broken branches and limbs from wind and in some cases wet snow. Also, temperatures having slipped into the upper 20s to very low 30s in many areas north and west of Boston early this morning has caused some ice patches to form in ground that was just wet last evening. This should melt and dry off during the day today as temperatures rise above freezing and wind and dry air work on the ground. But where some melting causes more puddles, watch for re-freezing and additional ice patches tonight. Winds diminish tonight as the Canadian low moves away. Our attention then turns to 2 things, an offshore storm developing later Monday and passing southeast of New England early Tuesday. This system is fully expected to be offshore for enough to avoid any significant impact, but its circulation will be large enough to create a northeast to north wind over Cape Cod that may carry some light showers of rain and/or snow across that area on Tuesday. In addition, a disturbance breaking off from a trough to our west will initiate some cloudiness for us here on Monday, and maybe enough for some snow showers Monday night and early Tuesday before the energy is absorbed by the offshore storm. At midweek, expect a dry and chilly Wednesday, but a disturbance moving rapidly southeastward may bring a few snow showers to the region Wednesday night and early Thursday, with a bit of a reinforcing shot of seasonably chilly air following.

TODAY: Cloud/sun mix. Slight chance of a passing sprinkle of rain or flurry of snow. Highs 35-42. Wind NW 15-25 MPH and gusty, diminishing late day.

TONIGHT: Mostly clear. Lows 18-25. Wind NW diminishing to under 10 MPH.

MONDAY: Partly to mostly cloudy. Highs 31-38. Wind variable up to 10 MPH.

MONDAY NIGHT: Mostly cloudy. Chance of snow showers. Lows 28-35. Wind NE to N 5-15 MPH except 15-25 MPH Cape Cod.

TUESDAY: Mostly cloudy to partly sunny. Chance of snow or rain showers Cape Cod. Highs 35-42. Wind N 10-20 MPH, higher gusts especially Cape Cod.

TUESDAY NIGHT: Mostly clear. Lows 20-27. Wind N to NW 5-15 MPH.

WEDNESDAY: Mostly sunny to partly cloudy. Highs 36-43. Wind variable up to 10 MPH.

WEDNESDAY NIGHT: Variably cloudy. Chance of snow showers. Lows 25-32. Wind NW 5-15 MPH.

THURSDAY: Partly sunny. Chance of snow showers in the morning. Highs 35-42. Wind NW 10-20 MPH.

DAYS 6-10 (DECEMBER 11-15)

High pressure brings fair and pleasant weather for December 11. The next low pressure system is set to impact the region on the December 12-13 weekend, but the track, timing, and intensity of the system is somewhat uncertain. The early idea is that low pressure may track through the Great Lakes and northern New England or nearby Canada, with a warm front trying to move through followed by a cold front. Frontal positions and timing in this scenario would be uncertain this far in advance, so for now just going to forecast a chance of some precipitation at times for the weekend. Fair, seasonably cold weather should follow this.

DAYS 11-15 (DECEMBER 16-20)

Watching December 16-18 as a window for potential storm threat (rain/mix/snow – still too early to know).

C-19 Chat Post – December 6 2020

DAYS 1-5 (DECEMBER 5-9)

The event is underway. Rapidly deepening and progressive low pressure will track northeastward, its center passing just southeast of or over Nantucket later today and into the Gulf of Maine tonight. While a mild air mass in place has resulted in this system starting as rain for all of the WHW forecast area, the process of rapid deepening and resultant banding of heavier precipitation, and generation of cold air aloft, will create a widespread dynamic cooling process, which is already underway and as of the time of this writing, the transition to snow has already taken place in southwestern NH and parts of central MA, and this will expand east and southeast with time, reaching Cape Cod and the Islands lastly where it may never completely change over to snow, before the precipitation shield, pivots and exits from southwest to northeast. The resultant bands of heavy snow, as much as 1 to 2 inch per hour snowfall rates, will lead to significant accumulations, especially where it snows longest. Look for the amount break-down below. We can’t discount the possibility of thunder occurring in the stronger bands of precipitation – something that is not unusual for such a feature. The low pressure center will cross the Bay of Fundy early Sunday then exit via the Maritime Provinces of Canada, leaving us blustery and chilly but dry weather in its wake. A quick look into early next week indicates we still need to watch low pressure offshore later Monday into Tuesday, but it still looks like it will be far enough offshore to avoid any significant impact. Will re-evaluate this for the next update.

TODAY: Overcast with rain changing to snow from west to east across the region, heavy at times, especially under banding zones where thunder is also possible. Temperatures falling to 28-35, coldest in interior southern NH and central MA, by late-day. Wind NE to N increasing to 10-20 MPH except 20-30 MPH coastal areas with gusts above 25 MPH possible interior areas and above 40 MPH coastal areas.

TONIGHT: Snow including heavy bands, except still some mix Cape Cod, slowly ending from southwest to northeast followed by breaking clouds. Total snowfall for the storm expected to be a slushy coating to 1 inch Cape Cod and Islands and immediate South Coast of MA & RI, 1-3 inches South Shore of MA (Plymouth) to southern RI just away from the shoreline, 3-6 inches Cape Ann MA and immediate MA coast through Boston to Providence RI mainly just east of I-95 down into southwestern RI, 6-10 inches NH Seacoast down I-95’s northern stretch to Boston’s Metro West to northwestern RI and eastern CT, as well as far southwestern NH, with 10-15 inches Worcester Hills through interior southern NH through the interior Merrimack Valley of MA. Lows 25-32. Wind N to NW 10-20 MPH with gusts 25-35 MPH.

SUNDAY: Cloud/sun mix. Passing light snow showers possible. Highs 33-40. Wind NW 15-25 MPH, higher gusts.

SUNDAY NIGHT: Mostly clear. Lows 18-25. Wind NW diminishing to under 10 MPH.

MONDAY: Partly to mostly cloudy. Highs 31-38. Wind variable up to 10 MPH.

MONDAY NIGHT: Cloudy. Chance of snow/mix/rain favoring the South Coast. Temperatures steady in the 30s. Wind NE 5-15 MPH.

TUESDAY: Cloudy start with a chance of snow/mix/rain favoring Cape Cod, then clearing. Highs 35-42. Wind N 10-20 MPH.

TUESDAY NIGHT: Mostly clear. Lows 20-27. Wind N 5-15 MPH.

WEDNESDAY: Mostly sunny. Highs 36-43. Wind variable up to 10 MPH.

DAYS 6-10 (DECEMBER 10-14)

Disturbance from the northwest brings a rain/snow shower risk December 10 with a brief shot of milder air then a shot of colder air with dry weather December 11. A frontal boundary and possible low pressure system brings the threat of unsettled weather back for December 12-13, with drier weather returning at the end of the period.

DAYS 11-15 (DECEMBER 15-19)

Watching December 16-18 as a window for potential storm threat (rain/mix/snow – too early to know).

C-19 Chat Post – December 5 2020

DAYS 1-5 (DECEMBER 4-8)

A cold front slips by today and low pressure develops on this front to our southwest, quickly organizing and strengthening as it tracks northeastward through Saturday, the center of a rapidly deepening low likely passing just southeast of Cape Cod Saturday night. For us, this will be a quick-hitting but fairly potent late autumn / early winter storm, starting as rain for all, from the South Coast this evening northward overnight into Saturday morning. As the storm center deepens and makes its closest pass then starts to pull away toward the Gulf of Maine, colder air will be drawn in from the north, and additional cold air will be generated aloft by the deepening process and brought toward the surface by the process of dynamic cooling (in which moderate to heavy precipitation drags the cold air down with it). This will change the rain over to snow, first during the midday hours of Saturday in the hills of southwestern NH and north central MA, then toward lower elevations and southeastward so that most areas with the exception of Cape Cod, the Islands, and the immediate South Coast will see snow before the precipitation exits in the early hours of Sunday. The highest snowfall amounts are likely to occur in areas that changed over first, as well as a band of more intense snowfall where the right combination of “just cold enough” and heaviest precipitation occurs. As the storm exits and moves away during Sunday, we’ll see windy and cold weather with a few snow showers possible in an otherwise blustery sun/cloud mix kind of day. Winds will quickly drop off Sunday night and early Monday as we get into a very weak ridge of high pressure between the departed storm and an evolving storm south of New England, which may graze the region Monday night and early Tuesday with some precipitation, although most indications are that this system will remain largely offshore. Still, we should keep an eye on it as it would not take much to “happen” in the atmosphere to draw it closer to this area. Later Tuesday, that storm will also be pulling away, leaving us with dry and chilly weather.

TODAY: Partial sun through lots of clouds morning. Cloudy this afternoon. Highs 48-55. Wind SW 5-15 MPH, gusts 20-25 MPH.

TONIGHT: Cloudy. Rain South Coast evening, spreading north overnight. Lows 40-47. Wind SW 5-15 MPH with higher gusts, shifting to N.

SATURDAY: Overcast. Rain all areas morning, changing to snow from northwest to southeast in all but the South Coast region during the afternoon. Temperatures falling to 28-35, coldest in southern NH and central MA, by the end of the day. Wind NE to N 10-20 MPH except 15-30 MPH Cape Cod with higher gusts possible in all areas, but especially coastal areas and higher elevations.

SATURDAY NIGHT: Overcast evening with snow, possibly heavy at times, except just rain mixing with snow South Coast, ending from southwest to northeast late evening and overnight followed by partial clearing. Accumulation of snow – slushy coatings South Coast, 1-3 inches Cape Ann southward along the immediate shoreline through Boston to the South Shore westward to Providence, 3-6 inches from the NH Seacoast down the northern portion of the I-95 belt to I-90 then westward from there into south central MA and eastern CT as well as northwestern RI, and 6-9 inches from the Merrimack Valley and interior southern NH through north central MA. Lows 25-32. Wind N to NW 10-20 MPH with gusts 25-35 MPH.

SUNDAY: Cloud/sun mix. Passing light snow showers possible. Highs 33-40. Wind NW 15-25 MPH, higher gusts.

SUNDAY NIGHT: Mostly clear. Lows 18-25. Wind NW diminishing to under 10 MPH.

MONDAY: Partly to mostly cloudy. Highs 31-38. Wind variable up to 10 MPH.

MONDAY NIGHT: Cloudy. Chance of snow/mix/rain favoring the South Coast. Temperatures steady in the 30s. Wind NE 5-15 MPH.

TUESDAY: Cloudy start with a chance of snow/mix/rain favoring Cape Cod, then clearing. Highs 35-42. Wind N 10-20 MPH.

DAYS 6-10 (DECEMBER 9-13)

High pressure brings dry but seasonably chilly weather for December 9. Disturbance from the northwest brings a rain/snow shower risk December 10 with a brief shot of milder air then a shot of colder air with dry weather December 11. A frontal boundary and possible low pressure system brings the threat of unsettled weather back for late in the period, December 12-13, but this is low confidence based on questionable performance of guidance.

DAYS 11-15 (DECEMBER 14-18)

Keep this a low confidence general outlook for a somewhat active pattern with 1 or 2 precipitation threats and variable temperatures averaging near to below normal.

C-19 Chat Post – December 4 2020

DAYS 1-5 (DECEMBER 3-7)

A westerly air flow aloft and high pressure south of New England combine for a very nice early December day today with relatively mild air and plenty of sun, but some high cloudiness will make an appearance in the sky only to increase the chances of a photogenic sunset in the 4 p.m. hour. 🙂 Tonight, more of those high clouds will steam in ahead of an approaching trough and cold front, which will bring even more cloudiness on Friday. Previously, I thought that some rain showers may accompany the passage of this front during the day on Friday but right now it looks like the front will come through dry, but moisture streaming northeastward ahead of our weekend storm threat may mean that some rainfall arrives by the end of the day or Friday evening, shortly after the front has gone by the area. And now onto the storm threat for the weekend – something we’ve been eyeing with great uncertainty for days. I wish I had a clearer picture of how this will unfold for today’s update, given that it’s not that far away, but there are still some questions to be answered. It does look like we’ll be looking at a system that impacts us throughout the day Saturday, making an exit Sunday. It will be a system that starts as rain through the entire WHW forecast area (southern NH, central and eastern MA, eastern CT, & RI). But there is going to be cold air available just to the northwest, as well as aloft, and we’re very likely to end up with a rain/snow line as this system moves through. The big question is how quickly and how far south and east does this rain/snow line get. I can say that the greatest threat for accumulating snow will be across interior southern NH and central MA based on current information, and the least of the threat will be across the South Coast and Cape Cod. But what happens between these areas? Further refining of this forecast is obviously needed, but my initial feeling is that these areas will at least mix with if not turn to snow at some point Saturday night or early Sunday, before precipitation departs, with some accumulation possible… Other impacts of the system not to be forgotten will be some strong wind and coastal flooding potential. More on that in the next update. Regardless of the details of the storm, behind it comes a period of windy and colder weather with a few lingering snow showers possible Sunday afternoon, and continued breezy and chilly but mainly dry weather Monday, with just a possibility of a few snow flurries migrating southeastward from the hills and mountains to the northwest.

TODAY: Mostly sunny. Highs 47-54. Wind W to SW 5-15 MPH.

TONIGHT: Increasing high clouds. Lows 35-42. Wind SW 5-15 MPH.

FRIDAY: Thickening high to middle overcast. Light rain possible by late-day mainly southwest of Boston. Highs 45-52. Wind SW up to 10 MPH shifting to NW.

FRIDAY NIGHT: Cloudy. Periods of rain. Lows 38-45. Wind N to NE up to 10 MPH.

SATURDAY: Overcast. Rain likely, with some mix/snow possible higher elevations of southwestern NH and north central MA by later in the day. Temperatures steady 38-45 then slowly falling. Wind NE 5-15 MPH inland and 15-25 MPH coastal areas with higher gusts especially in coastal areas and higher elevations.

SATURDAY NIGHT: Overcast. Rain southeast, rain/mix I-95 corridor, mix/snow to the northwest with accumulation possible. Lows 28-35 except 35-42 South Coast. Wind NE to N 15-25 MPH, higher gusts.

SUNDAY: Overcast with rain/mix/snow ending from west to east early – additional snow accumulation possible I-95 belt north and west. Becoming partly sunny with a few lingering snow showers thereafter. Temperatures generally steady mainly in the 30s. Wind N to NW 15-25 MPH, higher gusts.

SUNDAY NIGHT: Partly cloudy. Chance of passing snow flurries. Lows 18-25. Wind NW 15-25 MPH, higher gusts possible.

MONDAY: Partly sunny. Chance of passing snow flurries. Highs 30-37. Wind W 10-20 MPH, higher gusts possible.

DAYS 6-10 (DECEMBER 8-12)

Keeping an eye on a possible offshore storm December 8 – should stay offshore with dry/chilly weather here. Fair, cold start then a little milder December 9. Disturbance from the northwest brings a rain and/or snow shower risk December 10 then a shot of colder air with dry weather through December 11. Next jet stream disturbance may threaten the region with rain/mix/snow by the end of the period.

DAYS 11-15 (DECEMBER 13-17)

Precipitation threats early and again late in the period. Obviously with recent model performance and typical uncertainty this far in advance anyway, can’t elaborate on much at this point. Temperatures near to below normal.

C-19 Chat Post – December 3 2020

DAYS 1-5 (DECEMBER 2-6)

The big storm system that brought our wind & rain Monday and our continued windy weather yesterday will still have somewhat of a hold on the region in the form of a gusty breeze and passing clouds during today. Our air, a modified polar air mass indirectly from Canada via the Midwest, will feel more typical for early December. As a low pressure trough makes its way eastward, there will be an area of snow showers from the Great Lakes across New York, extending into the Berkshires, and a few of these, in the form of very light rain and/or snow showers, may sneak eastward far enough to survive into the WHW forecast area during the afternoon & early evening. That disturbance will be long gone by Thursday, which will be the “pick of the week” in terms of nice weather – sunshine, not too breezy, not too cold. And then things change. I’ve been trying to work out the timing of the threat of unsettled weather later this week for some time, and it still appears we’ll see the return of clouds and a rain shower threat Friday as a cold front moves into the region. The dilemma has been the weekend – would a storm develop and move in to impact Saturday, both days, Sunday, or would no storm impact the region at all? The answer seems to be revealing itself with gradual consensus developing between various model guidance to show that low pressure won’t waste that much time getting formed on the trailing portion of the front that passes through here, to our southwest, and then heads in this direction for the weekend. What still isn’t clear is the timing. The most likely scenario at this time seems to be a rain event beginning sometime Saturday, and ending, mostly as a mix or even snow for parts of the region during Sunday, pending the arrival of colder air. So as you see, there are still details to work out as we get closer.

TODAY: Sun and passing clouds. Chance of a brief light shower of rain or snow, favoring the hills well west and northwest of Boston later in the day. Highs 40-47. Wind SW to W 10-20 MPH with higher gusts.

TONIGHT: Partly cloudy with a brief sprinkle of rain or flurry of snow possible early, then clearing. Lows 28-35. Wind W 5-15 MPH.

THURSDAY: Mostly sunny. Highs 45-52. Wind W to SW 5-15 MPH.

THURSDAY NIGHT: Increasing clouds. Lows 35-42. Wind SW 5-15 MPH.

FRIDAY: Mostly cloudy. Chance of rain showers. Highs 45-52. Wind SW 5-15 MPH shifting to W.

FRIDAY NIGHT: Mostly cloudy. Lows 38-45. Wind variable under 10 MPH.

SATURDAY: Mostly cloudy. Chance of rain. Highs 45-52. Wind variable 5-15 MPH, higher gusts possible.

SATURDAY NIGHT: Cloudy. Chance of rain. Lows 35-42. Wind variable to NE 10-20 MPH, higher gusts possible.

SUNDAY: Cloudy with a chance of rain/mix/snow morning. Variably cloudy with a chance of mix/snow showers afternoon. Highs 38-45 then falling. Wind N to NW 15-25 MPH, higher gusts possible.

DAYS 6-10 (DECEMBER 7-11)

With the storm threat focus shifting to the weekend, the early portion of next week looks mostly dry and seasonably cold at this time, but we still may have to keep an eye on potential offshore low pressure. With low confidence I say that the next threat of precipitation is around December 10 from a system tracking west to east along the boundary of cold to our north and warmer air to our south.

DAYS 11-15 (DECEMBER 12-16)

Signal for another disturbance bringing a precipitation threat in the December 12-13 window followed by drier but colder weather. Again a low confidence forecast at this time.

C-19 Chat Post – December 2 2020

DAYS 1-5 (DECEMBER 1-5)

Discussion…

The final month of the year has arrived, and entered on a mild note on the heels of heavy showers and gusty wind last night. As upper level low pressure spins to our northwest today we’ll be mild and somewhat unsettled with additional showers possible, but cooler air will start to move in as the day goes on, not really noticed until tonight, and more so the following two days as the wind shifts more to the west. This cooler and dry air will arrive as the upper low exits via eastern Canada, but this means generally dry weather despite breezy conditions Wednesday and Thursday. By Friday, a cold front will cross the region with clouds and a chance of rain showers. When we get to the weekend, there are still some significant differences between models, but for now I will continue with the idea that high pressure will move in to give dry weather to us for Saturday.

Details…

TODAY: Variably cloudy. Scattered rain showers. Highs 57-64 occurring in the morning, then falling through 50s by late-day. Wind S to SW 10-20 MPH with higher gusts.

TONIGHT: Variably cloudy with a chance of rain showers evening. Partly cloudy overnight. Lows 32-39. Wind SW 5-15 MPH, higher gusts.

WEDNESDAY: Sun/cloud mix. Highs 42-49. Wind SW to W 10-20 MPH.

WEDNESDAY NIGHT: Mostly clear. Lows 28-35. Wind W 5-15 MPH.

THURSDAY: Mostly sunny. Highs 39-46. Wind W 5-15 MPH.

THURSDAY NIGHT: Increasing clouds. Lows 31-38 occurring in the evening. Temperatures may rise overnight. Wind W up to 10 MPH shifting to SW.

FRIDAY: Mostly cloudy. Chance of rain showers. Highs 45-52. Wind SW 5-15 MPH shifting to W.

FRIDAY NIGHT: Mostly cloudy with a chance of rain showers early, then clearing. Lows 28-35. Wind NW 5-15 MPH.

SATURDAY: Mostly sunny. Highs 40-47. Wind NW to N 5-15 MPH.

DAYS 6-10 (DECEMBER 6-10)

Storm threat exists for the December 6-7 time frame but details yet-to-be determined. Many possibilities on the table ranging from a storm track to our west with rain, a storm track over the area with mostly rain, maybe mix at end, a storm track a little further southeast with rain/mix/snow, and even a grazing or a miss. There’s even a chance that the system never quite forms. I’ll be working those details out over the next several days. Windy/colder weather around the middle of the period with a risk of snow showers then moderating temperatures later in the period based on current timing of larger scale features.

DAYS 11-15 (DECEMBER 11-15)

The overall idea for the middle of December is for potential active weather, including bouts of colder air, increasing the chance of some wintry precipitation events.

C-19 Chat Post – December 1 2020

DAYS 1-5 (NOVEMBER 30 – DECEMBER 4)

Discussion…

On this final day of November our main focus will be a storm system that will impact the region today, as well as into the first couple days of December, albeit much less so after this evening. The evolution of this system began over the weekend as a jet stream trough made its way eastward across the US. Surface low pressure developing near the western Gulf Coast region and has made its way northeastward as of this morning to a point it is about to move northeastward out of the Tennessee Valley then up the Appalachians and into the St. Lawrence Valley via New York State. The upper level system driving it is becoming a closed off low pressure area and as the surface storm maxes out while passing west of New England, a strong pressure gradient between it and offshore high pressure will result in a strengthening southerly wind flow across our area today. Also a significant ribbon of moisture will produce a significant bout of rainfall in the form of steady moderate to heavy rain ahead of a warm front then widespread moderate to heavy rain showers and embedded thunderstorms in the warm sector after the warm frontal passage and ahead of the cold front from midday through late evening. It is in the warm sector with the convective rainfall that the both the strongest gradient wind and strongest wind gusts will occur. If you have outdoor decorations, make sure they are secured as strong wind gusts could disturb them greatly. With trees mainly leafless, the chance of tree damage has dropped off, but some older, weakened trees may still come down or lose limbs, and this can result in some property damage and/or power outages. Street and parking lot flooding will be an issue due to heavy rain, and exacerbated where any leaves block storm drains. Coastal flooding will not be a significant issue as the tide should be shy of reaching its high for the night while the strongest winds occur, and this particular tide is not nearly as high as the series with saw with the new moon a couple of weeks ago. Once the axis of moisture gets beyond our region, the clouds will break and the air will remain quite mild overnight into Tuesday, but being on the eastern side of a closed low pressure area keeps us in the risk area for additional rain showers, although these should be just scattered. So December will start off feeling a bit more like a day in mid spring. As the upper low lifts its way into and through eastern Canada, our winds turn more westerly here Wednesday and Thursday, driving drier and seasonably chilly air into our area. By Friday, the next low pressure trough will be moving in from the west rather quickly (a little more quickly than previously anticipated) so the weather will be unsettled, mild enough for rain, but not nearly as stormy as the system we will see later today.

Details…

TODAY: Overcast. Rain arriving late morning through midday southwest to northeast, may be heavy at times during the afternoon. Highs 57-64 occurring late-day. Wind SE to S increasing to 10-20 MPH except 20-30 MPH coastal areas with higher gusts all areas by late in the day.

TONIGHT: Overcast evening with widespread rain showers and a chance of thunderstorms. Breaking clouds overnight with a chance of additional isolated to scattered rain showers. Lows 45-52. Wind S 15-35 MPH with gusts as high as 45-60 MPH evening (gusts above 60 MPH may occur in isolated coastal locations and higher elevations), shifting to SW 10-20 MPH with gusts 30-40 MPH overnight.

TUESDAY: Variably cloudy. Chance of rain showers. Highs 57-64 occurring in the morning, then falling through 50s by late-day. Wind SW to S 10-20 MPH with higher gusts.

TUESDAY NIGHT: Variably cloudy with a chance of rain showers evening. Partly cloudy overnight. Lows 33-40. Wind SW 5-15 MPH, higher gusts.

WEDNESDAY: Sun/cloud mix. Highs 42-49. Wind SW to W 10-20 MPH.

WEDNESDAY NIGHT: Mostly clear. Lows 28-35. Wind W 5-15 MPH.

THURSDAY: Mostly sunny. Highs 39-46. Wind W 5-15 MPH.

THURSDAY NIGHT: Increasing clouds. Lows 31-38 occurring in the evening. Temperatures may rise overnight. Wind W up to 10 MPH shifting to SW.

FRIDAY: Mostly cloudy. Chance of rain showers. Highs 45-52. Wind SW 5-15 MPH shifting to W.

DAYS 6-10 (DECEMBER 5-9)

A lot of uncertainty in this period. Watching the computer models try to “figure this out” has been interesting. Based on what I know through Friday, my best guess is the previous “weekend storm threat” actually holds off until the December 6-7 time frame with the first part of the weekend more likely to be dry. The storm that would result from the passage of a low pressure trough has a very questionable evolution and potential track, so it will be something to watch for now and I will once again try to pin down more detail as we get closer. A period of windy/colder weather would likely follow this threat (whether the storm impacted the region or missed it), perhaps with some snow showers.

DAYS 11-15 (DECEMBER 10-14)

Continuing to watch the potential for a colder and stormier period of weather in this time frame due to less high pressure in the US Southeast and a temporary disruption of the polar jet stream with indications for a fairly large scale trough of low pressure impacting the central and eastern US, including our region. Low confidence forecast at this time.

C-19 Chat Post – November 30 2020

DAYS 1-5 (NOVEMBER 29 – DECEMBER 3)

Discussion…

Stratocumulus? What stratocumulus? We’ve finally gotten rid of the low level moisture that, with the help of a couple of disturbances, had caused us abundant cloudiness the last couple of days, and today we get to enjoy a bright late November day as an area of high pressure slides just to the south of New England. While it won’t be warm like that stretch we had earlier in November, it will have a seasonable feel to it but with the lack of wind the air will be quite tolerable, so no more excuses to put off the last of the outside cleanup or putting up holiday decorations. But be warned, if you are putting up decorations vulnerable to strong wind, make sure they are anchored, as they will be tested for their “staying power” later on Monday. Low pressure forming near the western Gulf Coast is going to be propelled rather rapidly northeastward on the eastern side of a developing upper level trough. While we will be on the warm side of this storm system, it’s going to deliver us quite a dose of wet weather and strong southerly wind alter Monday, especially Monday evening. Once we get to Tuesday, the main belt of rainfall and strongest wind will have departed, but it will still be somewhat unsettled with a frontal boundary nearby and the trough to our west. So while a good portion of Tuesday may end up rain-free, I can’t rule out some passing rain showers with a fair amount of clouds crossing the sky, although the air will be mild despite a gusty breeze, which will be from a “mild” direction. We’ll have to wait until midweek, when the upper low shifts into eastern Canada, for some seasonably chilly air to arrive here. But it will do so with dry and breezy weather.

Details…

TODAY: Sunny. Highs 48-55. Wind W 5-15 MPH.

TONIGHT: Increasing clouds. Lows 35-42. Wind variable up to 10 MPH.

MONDAY: Overcast. Widespread rain showers arriving west to east by late morning or midday. Highs 57-64 occurring late-day. Wind SE to S increasing to 10-20 MPH except 20-30 MPH coastal areas with higher gusts all areas.

MONDAY NIGHT: Overcast evening with widespread rain showers and a chance of thunderstorms. Breaking clouds overnight with a chance of addition rain showers. Lows 45-52. Wind S 15-35 MPH with gusts as high as 45-60 MPH evening (gusts above 60 MPH may occur in isolated coastal locations and higher elevations), shifting to SW 10-20 MPH with gusts 30-40 MPH overnight.

TUESDAY: Variably cloudy. Chance of rain showers. Highs 57-64 occurring in the morning, then falling through 50s by late-day. Wind SW to S 10-20 MPH with higher gusts.

TUESDAY NIGHT: Variably cloudy with a chance of rain showers evening. Partly cloudy overnight. Lows 33-40. Wind SW 5-15 MPH, higher gusts.

WEDNESDAY: Sun/cloud mix. Highs 42-49. Wind SW to W 10-20 MPH.

WEDNESDAY NIGHT: Mostly clear. Lows 28-35. Wind W 5-15 MPH.

THURSDAY: Mostly sunny. Highs 39-46. Wind W 5-15 MPH.

DAYS 6-10 (DECEMBER 4-8)

Cold front moves through the region with a risk of rain showers December 4. Weekend storm threat December 5-6, odds favoring rain coast but rain and/or snow possible interior depending on the storm track and temperature profile. The track of that storm is highly uncertain. Guidance currently shows a few hundred mile spread in possibilities. Colder with a risk of snow showers December 7-8 behind the departing storm system.

DAYS 11-15 (DECEMBER 9-13)

Eyeing the potential for a colder and stormier period of weather in this time frame due to less high pressure in the US Southeast and a temporary disruption of the polar jet stream with indications for a fairly large scale trough of low pressure impacting the central and eastern US, including our region. While it’s too soon to pin-point any specific storm systems and their results, there is also the possibility that this pattern is even slower to evolve and that much of this period can be storm-free.