DAYS 1-5 (JULY 29 – AUGUST 2)
Boston can record an “official” heatwave with enough sun pushing their high temp to 90 today, but with highs of 91 & 90 the 2 previous days, this is hardly headline news. It’s July. What’s of more importance today is the threat of strong to severe thunderstorms with potential wind damage, instances of potentially large hail, and also areas of flash flooding possible from torrential rainfall. This is what the focus of today’s weather should be, not whether Boston’s high temp is 88, 89, 90, or 91. My prediction, by the way, is 89. So now that we have that taken care of, what’s the reason for the severe weather threat? Simple: Warm air, high humidity, cooling aloft, and an approaching disturbance and cold front. As higher dew points advect into the region this morning, some shower activity has been observed near the South Coast, but it looks like most of this will fade and move off to the east by mid morning and not really be a factor for a very long time. Much of the day will just end up rain-free, warm to hot, muggy, with a sun/cloud mix. While there can be a few isolated showers and thunderstorms popping up mainly from southern NH through the northern 2/3 of MA by mid afternoon, the “main event” looks a little later in timing, and its evolution may be a bit tricky. We probably see a fairly solid cluster or line of storms get going from NY to VT mid to late afternoon, then start an east southeastward march. But a dew point boundary and potential outflow boundaries from any advanced isolated cells make a region from around the Route 2 to I-90 corridors vulnerable to the eruption of new storms, and it’s entirely possible that this becomes the “new line” as the original one starts to weaken and “mush out” into a blob of more elevated convection. We’ll have to monitor the radar closely this afternoon to see how it goes. For this reason, I am leaning toward the Route 2 corridor southward as the most likely to see damaging storms with high winds and hail, as well as frequent lightning, which is not considered a factor in storm severity as far as warnings go. Any storm that contains lightning is a danger in itself, regardless of whether or not severe parameters are expected or achieved through hail 1″ or greater in diameter and wind gusts of 58 MPH or greater. The flash flood threat is greatest in areas that see torrential rainfall for more than just a few minutes, and in some instances where storms can train over the same region for a while it becomes a potentially bigger issue. In short, be on the look-out for storms and prepare to take action to protect yourself. Many outdoor activities on a summer weekend leave many vulnerable, so I can’t stress enough to keep an eye on the weather today! Regardless of the details of the event’s evolution, it will come to an end as storms exits via the South Coast and Cape Cod early tonight. While the South Coast & Cape are not immune to severe weather today, that region may be spared the worst with just a couple isolated stronger storms there in a more general area of showers – but like other areas keep an eye on trends. This is not strictly diurnally driven and sometimes enough of a boundary / lift of air in that region can keep storms going for a while. Tonight, a cold front sweeps through and the dew point which seems like it’s been 60+ forever will go to below 60 across the region, though it may take until mid or late morning Sunday to do so closer to the South Coast. Sunday will be a comfortable, rain-free day, but expect some diurnal clouds to pop up, more of the decorative variety. Monday’s weather looks fairly pleasant too. The dew point may tick back up a few degrees but really only to around 60 or just over it. This takes place ahead of a weak disturbance that may help initiate a quick shower over some locations during the afternoon or evening. This looks like a minor event, isolated in nature for showers, and favoring southwestern NH and central MA. Don’t cancel any Monday plans! We’ll welcome August with a sun/cloud mix but comfortable air Tuesday as a weak trough is still around but probably not enough for any showers. Wednesday, high pressure builds in surface and aloft with awesome weather!
TODAY: Variably cloudy. Isolated to scattered showers South Coast / Cape Cod until mid morning. Isolated to scattered thunderstorms possible mid afternoon and becoming more likely late afternoon mainly north of I-90. Widespread evening showers/thunderstorms. Any storms can be strong to severe with potential for damaging wind, large hail, frequent lightning, and flash flooding. Highs 85-92, cooler South Coast. Dew point upper 60s to lower 70s. Wind SW 5-15 MPH can be variable, strong, and gusty near storms.
TONIGHT: Variably cloudy. Showers/thunderstorms end by late evening, lastly near the South Coast / Cape Cod. Areas of fog forming. Lows 58-65. Dew point falling to upper 50s north of I-90 but still staying around or over 60 to the south. Wind variable becoming NW-N up to 10 MPH.
SUNDAY: A sun/cloud mix. Highs 77-84. Dew point upper 50s to lower 60s north to south, gradually decreasing during the day. Wind NW up to 10 MPH.
SUNDAY NIGHT: Mostly clear. Areas of ground fog in lower elevations. Lows 55-62. Dew point middle to upper 50s. Wind NW under 10 MPH.
MONDAY: A sun/cloud mix. An isolated shower possible by late-day mainly central MA and southwestern NH. Highs 78-85. Dew point around 60. Wind N up to 10 MPH with light coastal sea breezes.
MONDAY NIGHT: Partly cloudy early, then mostly clear. Lows 55-62. Dew point below 55. Wind variable under 10 MPH.
TUESDAY: Partly cloudy. Highs 76-83. Dew point below 60. Wind NW up to 10 MPH.
TUESDAY NIGHT: Clearing. Lows 56-63. Dew point below 55. Wind NW up to 10 MPH.
WEDNESDAY: Sunny. Highs 77-84. Dew point below 60. Wind W up to 10 MPH but local coastal sea breezes possible.
DAYS 6-10 (AUGUST 3-7)
Surface high pressure shifts to the east August 3 with fair weather and becoming slightly more humid. Trough / front from the west brings a shower/thunderstorm chance August 4. August 5-6 weekend looks mainly dry, less humid to start, more humid to finish, then some additional unsettled weather is possible by the end of the period with higher humidity. No significant heat expected.
DAYS 11-15 (AUGUST 8-12)
A weak westerly flow and weak trough much of the time in the region. This pattern is seasonable to cooler than normal with a couple shower chances, but not overly unsettled.