Friday Forecast

84 Comments

7:07AM

DAYS 1-5 (JULY 20-24)
High pressure hangs on for 2 more days with nice weather then low pressure developing along the US Southeast Coast in response to a trough over the Great Lakes and Ohio Valley swings up the coast then curls over the northern Mid Atlantic States on Sunday, bringing higher humidity and some wet weather to this area. High pressure building off the Atlantic Coast will push this ribbon of moisture more to the west early next week, when rain chances, while still there, will drop off significantly as humidity remains high. Forecast details…
TODAY: Mostly sunny. Highs 77-86, coolest in coastal areas. Wind light variable with sea breezes.
TONIGHT: Mostly clear. Lows 58-65. Wind light variable.
SATURDAY: Partly cloudy. More humid. Highs 77-86, coolest coastal areas. Wind light E to SE.
SATURDAY NIGHT: Clouding over. Showers arriving south to north overnight. Humid. Lows 63-70. Wind SE to S 5-15 MPH.
SUNDAY: Mostly cloudy. Showers likely. Chance of thunderstorms. Humid. Highs 72-80. Wind S to SE 10-20 MPH, higher gusts especially coastal areas.
MONDAY: Mostly cloudy with numerous to scattered showers morning. Partly sunny with scattered to isolated showers and thunderstorms afternoon. Humid. Lows in the 60s. Highs from the middle 70s to middle 80s, coolest coast.
TUESDAY: Partly cloudy. Isolated showers and thunderstorms mainly late day. Humid. Lows from the middle 60s to lower 70s. Highs from the upper 70s to upper 80s, coolest Cape Cod, warmest interior valleys.

DAYS 6-10 (JULY 25-29)
A large scale pattern of ridge West, trough Midwest / Great Lakes, ridge off East Coast means a period of higher humidity and opportunities for showers and thunderstorms on a daily basis, but these chances will be lowest July 25 and July 28, and a bit greater July 26, 27, and 29. Temperatures will run near to slightly above normal.

DAYS 11-15 (JULY 30-AUGUST 3)
A similar pattern should continue during this period.

84 thoughts on “Friday Forecast”

  4. Good morning and thank you TK.

    “Tornado Ted” is still at it at the Norton NWS office re: Sunday AM

    In addition to the flash flood threat, could see a few strong T-
    storms with gusty winds along with rotating thunderstorms vicinity
    of the warm frontal boundary late Sat night into Sunday morning.
    Concern here is strong low level shear combining with strong forcing
    for ascent and low LCLs as dew pts rise into the 70s as warm sector
    advances from south to north. Poor low level lapse rates may
    preclude stronger winds aloft from translating to the surface.
    However with dew pts rising into the 70s in the warm sector, this
    will lessen the low level inversion and also yield 500-1000j/kg of
    CAPE and may offset the poor lapse rates. Thus a high shear/low CAPE
    environment. Will have to watch this evolving system closely.

    Of note: the SREF significant tornado ingredients chart show ZILCH.

    SPC not impressed.

    https://www.spc.noaa.gov/products/outlook/day3otlk_0730.gif?1532090358879

    1. The NYC (Upton) NWS office now shows a bit of concern for a possible
      tornado and/or severe thunder storms.

      In terms of a severe thunderstorm threat, a low potential continues
      for isolated strong/damaging wind gusts or a weak tornado, in a high
      shear/low cape environment with 40-50 kt veering 950 hpa llj as the
      warm front makes its passage. As mentioned above, there is still
      uncertainty on timing/placement/weakening rate of core of an
      anomalously strong S llj of 50-60 kt at 950 hpa. But with moist
      adiabatic lapse rates in wake of warm frontal passage, potential
      exists to transport strong to damaging winds down to the surface in
      any isolated stronger convection within the llj axis. Will have to
      monitor evolution of llj/WCB over the next 24 hrs, as well as
      depiction of convection in the CAMs to get a better sense of where
      this threat may lie. At this point it appears it would be over E
      LI/SE CT and points east.

  8. Sad, sad story out of Missouri yesterday. Saw the video capturing the moments before the boat sank. The winds from the thunderstorm were causing ocean like waves in the lake.

    And wow with what happened in Iowa.

    I don’t know a lot about tornadoes, but I’ve heard of the term cold air tunnels and wonder if a few of the tornadoes yesterday were this type.

    In the videos I’ve seen, one tornado looked not like a cold air funnel. It had the traditional dark, dark ominous sky, etc

    Some of the other tornadoes though seemed to be occurring with partly cloudy skies, with the tornado or funnel dropping out of an individual, small cloud.

    I suppose it doesn’t matter what type of tornado it is, when it’s atop you, but it did seem like differing types of sky than you usually see.

    1. Yes, very sad, indeed. The boat should NEVER have been operating.
      Someone should lose their job(s)!!!

      re: Cold air funnels
      The video I saw from Eric looked like a normal full-fledged tornado
      replete with appropriate damage. Damage to me looked like strong EF-2
      or perhaps an EF-3. Not sure what the NWS assessment was. It was awesome
      seeing 2 of them at once.

      1. Yes, was that the one taking out the top of the tower or steeple ?

        That’s the one that looked like the usual monsters. Let me see if I can find/post a link or photo showing “the other ones”.

        1. Excellent. Would love to see them. Eric did not
          show those.

          Based on what you said, those others sound like
          the classic cold air funnel. Wasn’t part of the area
          sitting under the 500 mb closed low?

          1. https://video.search.yahoo.com/video/play;_ylt=AwrDQ2p871Fb.QMAckJEnIlQ;_ylu=X3oDMTByZjF2ZHFmBHNlYwNzcgRzbGsDdmlkBHZ0aWQDBGdwb3MDNw–?p=iowa+tornadoes+2018&vid=6d69041775383fff38c0af4eb1089ef0&turl=https%3A%2F%2Ftse2.mm.bing.net%2Fth%3Fid%3DOVF.ZU%252fnFkbG8jkzySzMvtjV8w%26pid%3D15.1%26h%3D337%26w%3D600%26c%3D7%26rs%3D1&rurl=https%3A%2F%2Fchicago.cbslocal.com%2F2018%2F07%2F19%2Ftornadoes-iowa-damage-injuries%2F&tit=Tornadoes+Sweep+Through+Iowa%3B+Major+Damage+And+Some+Injuries&c=6&h=337&w=600&l=96&sigr=127iavcpv&sigt=11se7vgch&sigi=12pk21acc&age=1532057121&fr2=p%3As%2Cv%3Av&hsimp=yhsm-vz&hspart=vz&tt=b

            Yes, the 500 mb feature that is about to bring us all that tropical humidity.

              1. Changed, sorry !

                I was explaining to Brian and Vicki last night how poor my skills are with copying links, etc 🙂

  11. Tom, thanks for the link. Watched the whole thing.

    So you met Vicki and Brian last night.
    By any chance did either of them show you the weather app? Just curious. 😀

    1. Yes, It is awesome.

      Looking forward to a version that will download onto an IPhone.

      It was great, they showed me the all the various things it could do.

      It was awesome !! Amazing job !!

      2. Doing some tweaks on it to make it look more professional.
        I don’t like all of those buttons on the opening page.
        Trying to leave the page pristine with a city icon (to change the city) and a menu icon on the tool bar with the name of the app
        in between the 2.

        In this manner, the display screen will remain totally clean.
        It will be a nested menu, so some menu items will open up a new menu. Should just make for a better presentation.

        After that, I will get back to the Iphone business.

        Before the upgrade to IOS11, I had it working for Iphone. (Vicki has the version in place at the time on her Iphone and Ipad)
        With the upgrade to ios11 it stopped working. Initial attempts to get it working failed. Frankly, I have not looked
        at anything to do with the Iphones since then. Too many
        other things going on. Not to mention, dealing with Apple is
        a big pain in the ass.

    2. It was a fun time and we talked a fair amount about your awesome work on your weather app as well as your great contributions on here. TK showed me the new additions to the android version of your app. I’m looking forward to the iPhone one but when you have time!!

  12. According to 12Z 3KM NAM, some decent convection rolling
    through Eastern MA Sunday AM:

    9Z

    http://maps3.pivotalweather.com/maps/models/nam4km/2018072012/045/refcmp.us_ne.png

    12Z

    http://maps3.pivotalweather.com/maps/models/nam4km/2018072012/048/refcmp.us_ne.png

    01km helectity

    9Z

    http://maps3.pivotalweather.com/maps/models/nam4km/2018072012/045/srh01.us_ne.png

    12Z

    http://maps3.pivotalweather.com/maps/models/nam4km/2018072012/048/srh01.us_ne.png

    So when that comes through the Boston area, we will have to be on the lookout.

    Let’s see what additional guidance has to say.

    1. The maps don’t necessarily mean severe.It just points out that this model shows convection with associated high levels of Helicity. I did not post, but it also shows very low levels of CAPE surface or elevated, which means a Highly sheared/low cape environment.

      Translation: ONLY and IF ONLY a decent enough thunderstorm
      were to develop, then it would be “possible” that it could rotate which
      then means there would be a “possibility” of an EF-0 or EF-1 short lived
      tornado.

      The risk is quite low, but it is non-zero.

      One more thing, imho, based on comparing the 9Z with the 12Z, the higher
      helicity looks to pass right through or just to the West of the Boston area.

      Not to alarm anyone, but the conditions are somewhat similar to
      the Revere tornado situation. Just something to watch for now.

  15. Since for Sunday AM, we are talking about a Low Cape/High shear environment,
    I decided to reach this phenomenon.

    Here is a rather technical paper on the subject (It is a very good read for those inclined) entitled:


    Climatology and Ingredients of Significant Severe Convection in High-Shear, Low-CAPE Environments

    https://journals.ametsoc.org/doi/10.1175/WAF-D-13-00041.1

    The reader’s Digest version of the conclusion of this report:

    Ultimately, a normalized product of the 0–3-km shear magnitude, 0–3-km lapse rate, and 700–500-hPa lapse rate was found to be the most skillful at discriminating between HSLC significant severe convection and nonsevere convection when using a fixed-layer shear.

  16. We can get an idea of the 0–3-km shear magnitude by looking at the
    0-3km helicity.

    However, where does one find these??? I do not see them on
    College of DuPage, pivotal or NCEP.

    0–3-km lapse rate, and 700–500-hPa lapse rate

    1. I just checked my Euro service and I actually have available:

      0–3-km shear magnitude, and 700–500-hPa lapse rate in addition
      to the helicity.

      The only one not available is: 0–3-km shear magnitude.

      Based on what I see from the 0Z run, we’re prime for an HSLC event.

      Waiting on the 12Z run.

  17. I’ve been following the coverage as they take Sgt Chesna from the church to the cemetery. There are hundreds and hundreds of people lining the streets, both sides of the highway and the bridge overpass. Heart wrenching doesn’t begin to describe.

    2. Our daughters were in the same class together. They are a really nice family. I was able to walk to the route today and yesterday. So many cops from all over new england. The family is getting a huge amount of support but will just need time to process everything.

      1. I ache. Law enforcement from all divisions in MA would have been represented including my sons. It’s a close family. The most important thing is to continue support. This hero was part of us all.

        The communities here seem close. I’ve noticed most flags here at half staff. I don’t always see that for personal flags

    1. I think that the risk area moves somewhat farther North. Plus the 3 day outlook
      has not been updated since this morning, so I look for this to change. We shall see.

      Looks to me that the SPC is monitoring for a possible LCHS event.

  19. I am hoping the rain comes after I come back home from Virginia tomorrow night.
    Weather today yesterday and Wednesday has been great. Temps in the upper 80s comfortable levels of humidity.

  20. Some supporting guidance for an HSLC event from my Euro Service:

    https://imgur.com/a/0a0YGDH

    Here is a complete explanation of the APRWX index used in the above linked map:

    http://www.aprweather.com/phpBB3/viewtopic.php?f=19&t=259

    Btw, interesting tidbit:

    I just Googled APRWX tornado v3.2
    Guess what hit I got? A reference and link to the Woods Hill Weather blog from
    2016 where I posted about this index.

    Here is the link:

    http://www.woodshill.net/?p=5651

    Here is the google page:

    https://www.google.com/search?safe=strict&rlz=1C1NHXL_enUS737US737&ei=iydSW5C0Fq2f_Qah84KQDg&q=APRWX+tornado+v3.2&oq=APRWX+tornado+v3.2&gs_l=psy-ab.12…13106.13106.0.14814.1.1.0.0.0.0.157.157.0j1.1.0….0…1c.1.64.psy-ab..0.0.0….0.NwwFJmWOybk

  21. 2:11 PM From NYC (Upton) NWS office re: Sunday AM

    In terms of a severe thunderstorm threat, a low potential continues
    for isolated strong/damaging wind gusts or a weak tornado, in a high
    shear/low CAPE environment with 40-50 kt veering 950 hPa LLJ as
    the warm front makes its passage.

  22. Iowa tornadoes: This situation was low top thunderstorms but with perfect wind shear conditions at low levels to produce strong tornadoes. It was kind of a compressed version of a classic set-up because of a stronger than average low pressure circulation in the region. The combination was perfect for the worst outcome. They were not cold air funnels. Cold air funnels almost never touch down, and when they do they cause minimal damage, if any at all.

  23. Before we get into the more active pattern upcoming, I was doing a little poking ahead and noting that the CFS and Euro have both let go of the idea of a cool August. They don’t have it blazing hot either, but they are no longer depicting a scenario that extends cooler air in northeastern and east central Canada down into the northeastern US. Not surprised. I think the upcoming pattern will hold into August for a while and we’ll see an oscillation of the position and a fluctuation of the strength of the ridge based in the western Atlantic during August. This may extend into September for a time as well.

    We are now seeing stronger signs of the result of El Nino arrival during the late autumn and early winter with the classic look to the pattern resulting in a mild Midwest and Northeast and a cool and stormier Southeast. We may end up with a northward displacement of things by mid winter which would allow a colder period despite El Nino conditions. Of course this hinges on many factors and is easily said but with very low confidence. It goes without saying that we have much time to study this and make a good winter forecast in a few months.

    I now return you back to your regularly scheduled beautiful summer day. 🙂

      1. No, we won’t have 70+ dp’s every day from Sunday to September. 🙂 But we will be in higher humidity quite often in my humble meteorological opinion.

    2. Thank you TK. I translated that to more of what we are having with the few HHH tossed in

      Last year this time you saw December snow. Anything in that glass ball of yours yet

      1. If I had to guess I’m going to say a very very slow start to the snow season (overall) and a winter quite devoid of precipitation overall. But there are a whole lot of factors to consider before I even bring that close to an actual “forecast”. 🙂

  24. Now the Norton NWS office is flat out talking about an early morning
    tornado on Sunday.

    A very strong low level southerly jet develops…on the order
    of 55-65 knots at 925-850 mb…after 2 AM Sunday. With backed
    easterly flow at the surface, low-level (0-1 km) helicity
    values are through the roof, with up to 400-600 forecast in
    western CT and 100-300 in the eastern portions of our area
    toward daybreak. Experience has shown that where a rapid influx
    of CAPE intersects with helicity values over 150, and with
    dewpoints soaring to the lower 70s by daybreak, the potential
    exists for an early morning tornado. This is especially true at
    this time of the year. The CAPE is forecast to reach 400-800
    J/kg in RI and southeast MA, possibly also northeast CT, by
    around 09Z, which is 5 AM. Thus, a threat exists for a possible
    tornado mainly from about 4 AM into the early daylight hours on
    Sunday.

    1. Similar set-ups have done it before so there is no reason to leave it out. Now we just need to hope the public doesn’t over-react. This set-up occurs a few times per summer and sometimes outside of summer around here.

      1. I just keep thinking about the revere tornado. It too was low risk, yet it did happen. I shall be looking just in case. Probably for naught, but that is a good thing.

  25. As I look at things more and more, the gloom & doom forecasts for “the week ahead” may look really bad after we only have a slug of rain early Sunday, scattered showers/storms part of the region later Sunday, scattered showers/storms Monday and Friday, and only isolated or no activity all the other days through the July 28-29 weekend.

  26. Jeremy R says

    Who’s ready for wicked humidity all next week?!?!….summer doing its thing.

    1. Well, Dave Epstein this morning never mentioned the word. I would say THAT is official. 😉

        1. Dave is every bit as good a forecaster as Eric is. Just one of them is a little more daring in tossing terms out. 🙂

  28. From SPC through 12Z tomorrow AM (8AM)

    Severe

    https://www.spc.noaa.gov/products/outlook/day1otlk_1200.gif?1532173190347

    tornado

    https://www.spc.noaa.gov/products/outlook/day1probotlk_1200_torn.gif?1532173001354

    Discussion

    …Northeastern US…

    Short-wave trough will eject north-northeast into southern New
    England during the latter half of the period. As a result, a
    pronounced surface low affiliated with this feature will lift north
    and move inland along the Middle Atlantic Coast before moving into
    southern NY by the end of the period. Shear profiles will increase
    markedly across coastal Middle Atlantic regions into southern New
    England but forecast weak buoyancy will likely negate robust
    updrafts within an otherwise favorably sheared regime for
    supercells. Will maintain 2% tornado probabilities for the
    possibility of a brief/weak tornado along coastal regions where
    moisture/instability will be somewhat more favorable for
    surface-based updrafts.

    1. From Norton NWS office

      Tornado / Waterspout…
      Potential for a brief spin-up. A high shear, low instability setup.
      Echoes of recent Concord and Revere early morning tornadoes which
      had a similar environment. Allegory to a landfalling tropical rain-
      band associated with a cyclone, the interaction with terrain and
      subsequent frictional component could potentially aid in a brief
      spin-up for the early morning period with any onshore thunderstorm.
      Then focus on later in the day within the warm sector. Continued low-
      level jet / shear within weak, subtle synoptic scale forcing as
      heights rise with the enhancing Atlantic ridge. Can`t rule out
      additional break-out midday into the afternoon activity. Low LCLs
      throughout with dewpoints getting into the mid 70s. SREF probs
      highlighting a high probability of exceeding 0-1 km helicity over
      150 m2/s2, and some indication of sigtor`s over 1.

      1. NCAR ARW WRF 15KM forecst for Vorticity Generation Parameter, 12Z Sunday.

        http://www2.mmm.ucar.edu/prod/rt/wrf/wrf20/2018072100/vgp.hr36.png

        .2 and above supports possible tornado.

        Vorticity Generation Parameter (m/s**2)
        The VGP Vorticity Generation Parameter) is meant to estimate the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft. Values greater than 0.2 m/s**2 suggest an increasing possibility of tornadic storms.

  29. Here is the Portland (Gray), ME take on this for their area:

    The severe weather threat on Sunday looks low. However, with
    very moist air mass in place, any substantial surface heating
    will result in weak to possibly moderate SBCAPE in the midst of
    moderate low level shear. This could possibly result in an
    isolated tornado or a few wind damage reports. Again, this is a
    low probability scenario, but non-zero.

  30. I awoke to delight conditions.
    Dew Point sitting at 55!!! Wow! I expected at least low 60s. I am thrilled!!!

    1. Nobody will really feel an increase in humidity until this evening. Daytime is dry.

      1. Sounds good and thanks. Listening to Eric last night, it sure
        sounded like more humid today. 😀

  31. A little reality check…
    We have setups like this periodically just about every summer (and other times of the year as well). They virtually all present a somewhat similar “tornado risk”. The thing is, the weather is under such intense scrutiny now and everybody hinges on every word and every term. Are they gonna say it? Are they? It’s exciting, sure, from an entertainment standpoint. But, in the end, it’s just as it’s always been – weather forecasting and observation. And with that said, I am now updating…

  32. NWS may find they over-forecast clouds many days in the coming week. “Mostly cloudy” can be replaced by “partly sunny” or “partly cloudy” in many of those and will turn out more accurate.

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