Monday Forecast

69 Comments

7:24AM

DAYS 1-5 (MAY 14-18)
The warm-up will occur early this week as expected, but don’t expect 2 completely sunny days to go along with it, as today starts with some cloudiness and Tuesday winds up with a shower and thunderstorm threat. This will lead us to an unsettled period of weather mid to late week as the front that is pushing through as a warm front today comes back as a cold front later Tuesday and then sits just south of or over southeastern New England Wednesday through Friday. Forecast details…
TODAY: Variably cloudy into late morning then clearing midday and afternoon. Highs 60-67 coast, 68-75 interior. Wind S to SW up to 10 MPH.
TONIGHT: Partly cloudy. Patchy fog interior valley areas. Lows 52-59. Wind SW up to 10 MPH.
TUESDAY: Partly sunny. Chance of showers and thunderstorms midday through late afternoon, best chance north and west of Boston. Highs 68-75 South Coast, 76-84 elsewhere. Wind SW 10-20 MPH.
WEDNESDAY THROUGH FRIDAY: Mostly cloudy daily. Episodes of showers. Lows in the 50s. Highs in the 60s, coolest coastal areas.

DAYS 6-10 (MAY 19-23)
With the weather pattern likely putting southern New England in a zone between cool Canadian air and warm air from the Mid Atlantic to Southeast US, episodes of unsettled weather are likely, but don’t cancel any plans as there will be stretches of nicer weather amidst it.

DAYS 11-15 (MAY 24-28)
Leaning toward unsettled early period then a drying and warming trend.

69 thoughts on “Monday Forecast”

  3. Thanks TK.

    Tomorrow could be rather interesting. I agree with the general line of reasoning in the NWS discussions from BOX and OKX. The mesoscale guidance is fairly aggressive on bringing thunderstorms into most of SNE. The best chances should remain both northwest and southwest of SNE. I could see storms surviving until fairly close to the coast because the frontal timing is favorable, but they shouldn’t make it all the way to the coast. Biggest threat should be damaging winds, with multi-cellular and linear/quasi-linear storm mode favored. Hail will also be possible. Tornado threat looks pretty low with primarily uni-directional shear and a fairly high LCL.

    I don’t really agree with the SPC outlook right now. I think the slight and marginal risk areas should be expanded well north of where they are, probably right up into central New England, and just leaving out the coastal areas. We’ll see how things shake out over the next 24 hours.

    1. Thanks WxWatcher. We shall see.

      Re: tornado threat
      I was looking at some pretty high helicity numbers, so the threat would
      Not be zero by any means. Low? Perhaps, however, I look for that to change.
      I see a possible tornado threat West Of Worcester. Certainly not in the coastal plain. Will be watching.

      1. I generally agree. There could be a localized, conditional zone of enhanced tornado potential along a triple point-like feature with a weak low along the front, and if it happens it would more likely occur in southern or even central New England as opposed to the mid-Atlantic states. LCL height would still be a limiting factor though. As usual around here, we just have to watch the trends.

        1. Agree with LCL height. Looking at the helicity, specifically the crossover chart, the best shear is up to 500MB. Like you said more uni-directional surface to 850MB. However, bulk shear is 60 knots. Get a severe storm going and anything can happen.

          I just keep my eye on these kind of situations.

          I am waiting for the 9Z SREF. 3Z Sref had
          significant tornado parameter at 2 for Western MA
          and significant tornado ingredients in the 15% zone.
          Had the 5% to the coast. Small numbers, but for some
          reason for New England they can be meaningful.

          I want to monitor that for changes one way or the other.

  6. Well not liking the look for Saturday at this point. Starting to look at indoor options but will until TK tells me otherwise 🙂

  9. Thanks TK
    I am surprised SNE that most of SNE with the exception of eastern SNE is not in a marginal or slight risk from the SPC. Looking at some of the computer guidance there is at the very least a marginal threat for severe weather. Will see what happens when the SPC updates around 1:30pm today.

    1. Thank you JJ. Always enjoy reading these posts and I very much appreciate it that you share these.

      Interesting day shaping up, again, most especially inland.

  11. 9Z SREF

    CravenBrooks Severe

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_CB_MEDIAN_MXMN__f033.gif

    Helicity, 0-1km

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_1KMHEL_SSB_MEDIAN_MXMN__f033.gif

    Helicity, 0-3km

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_3KMHEL_SSB_MEDIAN_MXMN__f033.gif

    Significant tornado Parameter

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_SIGTOR_MEDIAN_MXMN__f033.gif

    Significant Tornado Ingredients

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_prob_combined_sigtor__f033.gif

    That would be border-line for tornado watch issuance, probably just a tad short.
    We’ll see what later runs show.

  12. When the SREF highlights a certain area for tornado potential you start to pay attention. The high LCL’s may limit this potential as was discussed in NWS Upton, NY discussion earlier. Mid level rates on both 6z runs of NAM and GFS are impressive and I don’t remember seeing values like that at any time we had thunderstorms. I believe the highest the mid level rates got to was just over 6.0

  15. Looking over the 12Z 3KM NAM, I am becoming somewhat concerned about
    tomorrow.

    It has CAPES to near 2,000 joules even for Boston with LI of -6 to -8, yes even for Boston. However, LCL levels are still quite high at over 1,000 m. Looking at the cross over chart, it now show significant shear from surface to 850MB. Bulk shear over
    53 kts.

    Likely not a tornado situation (although it can’t be totally ruled out), but severe weather appears to be on the table.

  16. I will be very surprised if the SPC keeps all of SNE in general risk area for tomorrow considering what the latest NAM and SREF are showing. Update from the SPC around 1:30pm.
    What JPDave just posted about the 12z 3km NAM more than enough instability for thunderstorm development tomorrow. The parameters are not extreme but are impressive. The mid level lapse rates on the regular 12z NAM were higher than anytime I could remember last summer when we had thunderstorms. Most areas showing great than 6.5 and a lot of areas around or over 7.0 for tomorrow.

  17. There appears to be and someone correct me if I am wrong an elevated mixed layer in place. The last time I remember an elevated mixed layer in place for thunderstorms was back when we had that night time severe weather outbreak in February 2016.

    1. One of your CT Mets mentioned EML in a tweet.

      Something is cooking for tomorrow for sure. May not reach the coast, but
      inland areas may be under the gun. Will still have to watch for the coast, but
      we know what that marine influence from South of us does. Will have to watch
      that wind direction. Looks to be generally a SW wind, however with a bit
      more Southerly component towards the coastal plain. This alone would be
      enough to spare coastal areas. We still need to watch.

      If this were mid-July, I’d be much more concerned.

      buoys South of LI, both on the Western edge and Eastern Edge a little
      above 52 F. That will do it.

  20. Any wind off that cool water thunderstorms kryptonite as thunderstorms hate stable air.
    Interior parts of SNE could be a different story.

    1. We can “almost” say that coastal areas will NOT have severe weather
      tomorrow, but it can’t be totally ruled out. Will be watching closely, especially
      that wind direction and also temperature and DP.

      NAM forecast is for DP around 65 and temp around 85 for tomorrow PM.
      That “could” be a contributing factor, thus the need to watch.

  21. Tweet from John Homenuk for tomorrow’s thunderstorm potential
    The very impressive signal for severe weather in the Northeast on Tuesday continues today. The latest HREF paintballs are signaling the development of intense updrafts in W New England followed by the development of a severe convective complex turning southward.

  23. SPC not ruling out a couple tornadoes somewhere in the interior parts of the Northeast.
    While background near-surface winds will generally be veered and not particularly strong, localized backing in area valleys and/or ahead of line-embedded vortices may favor a couple of tornadoes as well.

  27. Will be interested to see the latest SREF model run when it comes out this afternoon.

  28. Sref finally far enough out.

    Significant tornado ingredients

    18Z

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_prob_combined_sigtor__f027.gif

    21Z

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_prob_combined_sigtor__f030.gif

    Significan tornado parameter

    18Z

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_SIGTOR_MEDIAN_MXMN__f027.gif

    21Z

    http://www.spc.noaa.gov/exper/sref/gifs/latest/SREF_SIGTOR_MEDIAN_MXMN__f030.gif

    The significant tornado parameter has 1 into the Boston area. This is an increase
    since the 9Z run.

    1. Hmmm….

      TK, do you agree. Would this be possible, considering the marine influence???

      NWS seems to disagree with the Good Mr. Fisher.

      Overall something to watch for Tuesday, with a particular focus
      along or S of the Mass Pike given current timing. However,
      portions of SE MA and RI may be limited by the onshore flow and
      marine layer influence.

  30. Remnant EMLs are often associated with our most extreme severe weather days in SNE, and for good reason. 6-1-11 is the best example, although there have been several others. It doesn’t happen that often though; only a handful of days per year on average do we actually get a true remnant EML that reaches us from the Rockies. The setup for tomorrow is very interesting and quite unusual in that regard. I think there will be enough limiting factors to prevent a big outbreak, certainly when it comes to tornadoes. Still have the high LCL issues, and the best shear overlap with the instability is likely to be more uni-directional as opposed to rotational. But we will surely see watches and warnings going out tomorrow, and an active day is likely especially for central and western portions of SNE.

  31. Even without a tornado you get a thunderstorm with straight line damaging winds coming through your neighborhood it will leave its calling card.

    1. I still think that there will be a tornado or 2 somewhere in SNE, most likely
      West of Worcester somewhere, but who knows. We get a rip roaring severe thunderstorm going and anything can happen.

    2. In cases of an F0 or F1 tornado, sometimes the Straight Line wind damage can be more serious and wide spread, all depending of course.

  32. If I am reading things correctly, 18Z NAM is indicating a good deal of
    elevated CAPE in Eastern and SE SNE, while large SB CAPE values in Western
    section.

    I know that elevated CAPE would allow for thunderstorms, but would that
    limit them to sub-severe levels? OR is it possible to get a severe thunderstorm
    with mostly elevated CAPE?

  34. I know its one model run but looking at the 18z NAM run and will see if others show this but one could argue you could bring that enhanced risk back to NYC area and northern NJ.
    JPDave just saw Ryan Hanrahan comment on a tweet from John Homenuk and he said commenting on the 18z NAM 0-1km winds looked more back.

    1. What does this mean?

      18z NAM 0-1km winds looked more back.

      Looked more back???

      Back what? Back to more shear? more helicity? More of a threat?
      we’re missing something there.

  36. That is simulated Infra Red Satellite imagery display.
    Darker reds indicate higher cloud tops which means more intense thunderstorms, I presume.

    1. Yes, but keep in mind if you have rapidly developing storms the anvils are going to be cold over a large area so you can be under a “red” spot and have just an overcast sky with nothing happening. It will depend on where each storm tower is, or whether or not we have a line, or a cluster, or whatever the set-up is.

  38. I miss real thunderstorms and tornadoes back home. Pretty rare up here. No dry line to speak of and the marine air kills them.
    I watched one in the air pull the air handlers off the top of the athletic center and toss them across two parking lots.
    Rode another big one out in the walk-in fridge in a coffee shop once.
    Hail the size of baseballs beat the roof off our house a twice when I was a kid. Beat the roof off again a few years ago on my moms house.
    I miss a real storm outbreak. 🙁

    1. i call it lucky, we don’t generally have extremely destructive tornado’s. Its one of the many reasons why I would never live in the center of this country. Also No ocean.

  39. Every piece of new information I see makes me more concerned about tomorrow. I’d be very interested in TK’s thoughts, but I don’t see how you get a much better setup for severe weather around here. I especially like the remnant EML and the timing of the front to take advantage of peak heating. Certainly plenty of shear and sufficient moisture as well. Everyone likes to jump straight to the tornado threat, but that’s always a crapshoot around here, and there are still a couple things that will limit the tornado potential tomorrow. I think the point is that widespread strong to severe storms seem likely, especially in/around central and western parts of SNE, and the specific hazards can be addressed as they play out.

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