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Saturday, July 2, 2022 SEVERE Potential


weatherwiz
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A warm front is set to lift northeast across New England Thursday night through Friday morning ushering in a much hotter and more humid airmass. Several weak disturbances will cross the Northeast Friday which may spark off isolated afternoon showers and thunderstorms with scattered showers and thunderstorms possible Friday night. All eyes then turn to Saturday...

A substantial longwave trough moves across southeastern Canada through the day Saturday with a belt of strong westerlies traversing much of New England. An elongated cold front extending from near Hudson Bay through southeast Canada and into the Ohio Valley will advance southeast through the day Saturday with a pre-frontal trough becoming established across the Northeast. Out ahead of these features and very warm and humid airmass is expected with surface temperatures climbing into the lower 80's with dewpoints well into the 60's. While poor mid-level lapse rates will tamper instability, the combination of temperatures into the 80's and dewpoints well into the 60's should contribute to 1000-1500 J/KG of MLCAPE.

Forecast models indicate 30-50 knots of mid-level flow traversing the region (though weakening through the afternoon). Despite the fact the stronger shortwave forcing is along and north of the International border, modest mid-level flow should help contribute to storm organization ahead of the pre-frontal trough. As such multiple lines of showers and thunderstorms are expected develop and traverse southern New England Saturday afternoon into the evening. 

Given MLCape values on order of 1000-1500 J/KG the potential will exists for some of the thunderstorms to become severe. Despite the rather modest low-level winds characterized by 850mb winds <30 knots, forecast models develop steep low-level apse rates >8.5 -9 C/KM. These lapse rates, combined with the moderate buoyancy would support the potential for scattered wind damage. While flow is modest in the low-levels, some forecast models indicate some low-level directional shear becoming present in the vicinity of the pre-frontal trough. As such an isolated brief tornado would also be possible with the highest potential from southern New Hampshire into Worcester County. 

WE NEED SEVER!!!!!!!!!

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CAMS struggling to develop much in the way of convection tomorrow. Looks like there could be a little bit of shortwave subsidence behind early morning activity. Also wonder if there could be some minor capping issues too. The mid-level lapse rates are certainly garbage but mid-level shear is looking healthier. Not sure how widespread convection will fire 

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20 minutes ago, weatherwiz said:

CAMS struggling to develop much in the way of convection tomorrow. Looks like there could be a little bit of shortwave subsidence behind early morning activity. Also wonder if there could be some minor capping issues too. The mid-level lapse rates are certainly garbage but mid-level shear is looking healthier. Not sure how widespread convection will fire 

I hope that it’s eventful enough that the Hallmark Channel will make a movie about it someday and call it “Night of the EF0”  starring John Schneider 

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 Ahead of the front, a seasonally moist airmass will be in place,
   with mid/upper 60s F dewpoints common. While midlevel lapse rates
   will remain modest, heating into the 80s F will support 1000-2000
   J/kg MLCAPE. Deep-layer flow will remain mostly unidirectional,
   though increasing speeds with height will support 35-45 kt effective
   shear magnitudes across the Mid-Atlantic and southern New England.
   As a result, organized supercells and bowing clusters are possible.
   Steep low-level lapse rates and high PW values, combined with rather
   weak low-level shear will favor damaging gust potential. Modest
   lapse rates and somewhat warm temperatures aloft will limit the
   large hail potential, but any organized/sustained supercell could
   produce marginally severe hail. 
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* A approaching cold front will bring strong to severe thunderstorms
  Saturday afternoon and evening.

Saturday: SPC continues to include much of southern New England
under a slight risk for severe weather, with the main threat being
straight-line damaging winds. During the morning, anticipating
mainly elevated convection with a threat of for locally heavy rain.
During the afternoon, surface-based instability increases to 1000-
2000+ J/kg, with with 35-45 kts of shear, while a cold front
approaches and passes through much of SNE. Ahead of the cold front,
we maintain 1.5-2 inch PWATs, thus locally heavy rainfall is
expected. This could produce urban and poor drainage flooding. It
should be noted that with the 12Z CAMs, they have backed off some on
the areal coverage of convection across SNE, will need to keep an
eye on future runs. At this time, the greatest threat for severe
weather looks to be across northern CT, thru central RI and SE MA in
the afternoon/early evening.
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28 minutes ago, Torch Tiger said:
* A approaching cold front will bring strong to severe thunderstorms
  Saturday afternoon and evening.

Saturday: SPC continues to include much of southern New England
under a slight risk for severe weather, with the main threat being
straight-line damaging winds. During the morning, anticipating
mainly elevated convection with a threat of for locally heavy rain.
During the afternoon, surface-based instability increases to 1000-
2000+ J/kg, with with 35-45 kts of shear, while a cold front
approaches and passes through much of SNE. Ahead of the cold front,
we maintain 1.5-2 inch PWATs, thus locally heavy rainfall is
expected. This could produce urban and poor drainage flooding. It
should be noted that with the 12Z CAMs, they have backed off some on
the areal coverage of convection across SNE, will need to keep an
eye on future runs. At this time, the greatest threat for severe
weather looks to be across northern CT, thru central RI and SE MA in
the afternoon/early evening.

Models look awful . Stein 

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Recent hi res visible satellite loop/trends finally show some tendency to break up this 'tube' of convection dumpster juice ...

That's step one in substantiating this thread - LOL, or forget it.   

If we can do so sooner rather than later, and get thermal recovery going here over the next hour, that allows even asking the 2nd question:  is that enough?  

It could be in time to destablize.  In reading the SPC stuff, the mechanics are not overwhelming, but there is some unidirectional forcing.  There is no question that SB CAPE would balloon if the sun floods through this decaying linear cloud scung.   But my own rule of thumb for convection around here is that we tend to really need mid level lapse rates to be sloped.  It seems the CAPE has a chance to be anomalously high, so that may offset ... but we gotta get the f'n sun shining here quick.

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