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Rain/Wind/Isolated Thunder Event: April 19-20


Quincy

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Due to the timing of a cold front and marginal to no instability, this does not look like a severe weather scenario.

 

However, some strong winds associated with the frontal passage are definitely possible. Temperatures can rise into the 70's on Friday, assuming the region gets at least some partial sunshine. 

 

Current thinking is isolated showers/storms Friday night and then heavy rain and thunder for a time overnight. Clearing out during the day on Saturday.

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If the NAM is correct we will be dealing with a decaying squall line around midnight tonight west of the city. We have broken out in full sunshine which should allow for at least some slight instability to build in.

The NAM is still showing this, although there is some question of how the line can hold together once it reaches the Appalachians. This is especially true due to the nighttime time-frame of this happening.

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I think the severe weather threat is very limited...you could even argue that the threat for thunder is limited east of NYC as well. The timing of the front is poor and we're holding on to an elevated instability axis over Western NJ through 06z...so there could be some embedded storms as the front comes through. But I think this will be a burst of heavy rain with some rumbles of thunder and very limited severe weather reports as far as strong winds go. 

 

You can see the effect that the S winds have on Long Island with the thermal gradient east of NYC

 

temp30.gif

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I think the severe weather threat is very limited...you could even argue that the threat for thunder is limited east of NYC as well. The timing of the front is poor and we're holding on to an elevated instability axis over Western NJ through 06z...so there could be some embedded storms as the front comes through. But I think this will be a burst of heavy rain with some rumbles of thunder and very limited severe weather reports as far as strong winds go. 

 

You can see the effect that the S winds have on Long Island with the thermal gradient east of NYC

 

temp30.gif

Agree-looks like the marine layer will be a problem for eastern areas. Although, the last T-storm event was able to make it to the coast, the instability doesn't look too promising.

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I think the severe weather threat is very limited...you could even argue that the threat for thunder is limited east of NYC as well. The timing of the front is poor and we're holding on to an elevated instability axis over Western NJ through 06z...so there could be some embedded storms as the front comes through. But I think this will be a burst of heavy rain with some rumbles of thunder and very limited severe weather reports as far as strong winds go. 

 

You can see the effect that the S winds have on Long Island with the thermal gradient east of NYC

 

The NAM has elevated CAPE, increasing for eastern areas, with a strengthening southerly LLJ, early tomorrow night.

 

974t4m.jpg

 

 

2lq3rr.jpg

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Are we going to be able to clear out though?

 

I would think so once the winds shift to southerly. The NAM shows this pretty well. Notice how the southerly and maybe slightly SSE component to the wind keeps a low cloud bank near the shores, but only high clouds over NJ which allows for the big warmup ahead of the approaching front in a small warm sector.

 

http://www.meteo.psu.edu/~fxg1/NAMSFC4_6z/rad15.gif

 

temp11.gif

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I have an inclination there will be a borderline severe if not severe outflow boundary (due to winds) across NYC/LI that outraces any updrafts from a squall line associated with the front in NJ late this evening/tonight. This event seems to have that kind of signature.

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We're really clearing out here now and visible satellite confirms that this continues to spread north and east. 

 

Noticing an increase in surface based and elevated cape on SPC mesoanalysis which is juxtaposed with some modestly favorable 0-6km bulk shear. We've got several hours before the best forcing arrives...but not a bad trend so far today. 

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