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Friday, May 15, 2020 Severe Weather Potential


weatherwiz
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Been meaning to start this thread since Monday but I was all threaded out. Anyways, severe weather season is starting to get very active around here as we have another threat right around the corner...and this one comes with our first early taste of late spring or early summer as a warm front tickles us and we taste some humidity. Obviously, this early in the season the biggest question is northward warm front progression. It does appear the warm front will at least push into central New England. South of the warm front dewpoints should get into the lower 60's. While not great, mid-level lapse rates will be around 6.5 C/KM. With surface temperatures perhaps pushing into the 70's we should generate enough instability, when combined with ample wind shear to produce the development of t'storms; including the risk for some strong-to-severe t'storms. 

As usual with this type of setup and time of year, the greatest risk will be away from the marine influence. When considering timing of the fropa or pre-frontal trough the greatest potential will likely be eastern PA, southeast NY, southern VT, and western MA/CT. Strong winds aloft, inverted-V sounding signatures, and linear storm mode indicate main severe hazard will be damaging wind gusts. However, in the vicinity of the warm front there will be enough backing of the llvl winds to yield the risk of rotation and an enhanced risk for hail or a brief tornado. 

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40 minutes ago, weatherwiz said:

Been meaning to start this thread since Monday but I was all threaded out. Anyways, severe weather season is starting to get very active around here as we have another threat right around the corner...and this one comes with our first early taste of late spring or early summer as a warm front tickles us and we taste some humidity. Obviously, this early in the season the biggest question is northward warm front progression. It does appear the warm front will at least push into central New England. South of the warm front dewpoints should get into the lower 60's. While not great, mid-level lapse rates will be around 6.5 C/KM. With surface temperatures perhaps pushing into the 70's we should generate enough instability, when combined with ample wind shear to produce the development of t'storms; including the risk for some strong-to-severe t'storms. 

As usual with this type of setup and time of year, the greatest risk will be away from the marine influence. When considering timing of the fropa or pre-frontal trough the greatest potential will likely be eastern PA, southeast NY, southern VT, and western MA/CT. Strong winds aloft, inverted-V sounding signatures, and linear storm mode indicate main severe hazard will be damaging wind gusts. However, in the vicinity of the warm front there will be enough backing of the llvl winds to yield the risk of rotation and an enhanced risk for hail or a brief tornado. 

NAMNSTNE_con_uphlysw_060_zpskivfpycg.png

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let's go

   ...Northeast States...
   A northern-stream shortwave trough is forecast to progress quickly
   eastward/southeastward across the Great Lakes into the Northeast
   States on Friday. Strong mid-level flow attendant to this system
   will spread eastward just ahead of it while an associated surface
   low and cold front also move across the Northeast. Temperatures and
   dewpoints ahead of this front are forecast to reach the mid 70s and
   upper 50s/low 60s, respectively, resulting in modest instability.
   Thunderstorm development is anticipated during the afternoon as the
   front interacts with this instability. Low to mid-level flow will
   strengthen over the region as the shortwave trough approaches,
   contributing to both moderate vertical shear and fast storm motions.
   Fast-moving bowing line segments, which may eventually amalgamate
   into a coherent convective line, will be the predominant storm mode.
   Damaging wind gusts from these bowing segments will be the primary
   severe hazard, although some isolated hail may occur, particularly
   with any more cellular/discrete storms. Additionally, moderate
   veering of the low-level wind profiles will support a low-probably
   tornado potential with both discrete development ahead of the line
   and line-embedded circulations.
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16 minutes ago, ineedsnow said:

First slight risk of the year..  congrats paul

I am a bit shocked it's so far east. I think the greatest overall potential is to our northwest. What kinda sucks for us is timing but there seems to be enough instability left to keep the threat for damaging winds through the I-84 corridor. 

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4 minutes ago, CoastalWx said:

Looks like a lot of the action is along warm front and even near backdoor front.

 

2 minutes ago, CoastalWx said:

Decent s/w support for storms on the cold front in the evening though. Definitely an interesting day I think. 

Definitely agreed the warm front could be a pretty decent focal point...especially if any convection can form along it. There definitely seems to be at least enough support to keep a line of t'storms moving into the region (even after sunset) but I think the overall greatest potential for severe wx is going to be just west of us...I think timing kinda hurts us. That strong piece of vort tracking into NNE happens just a bit too late. 

It would seem like the greatest chance for any severe associated with the warm front would be mid-to-late afternoon, however, there may not be much overall support for developing convection then. Strongest height falls seem to arrive shortly after the best ingredients would be in place. 

But we should certainly see some scattered wind damage tomorrow!!! 

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Ok. I'm intrigued. Let's see how today's convection can screw this up.  Most models have today's leftover convection passing offshore before 12z tomorrow morning. Hopefully it's out of gas, otherwise we run the risk of it throwing a backdoor well inland and beating back the warm front.  But also....we may need that morning convection to add a little extra moisture to the air. Boy it is dry out there today.

For those in eastern SNE, it is most certainly a race between convection and a potential backdoor.  Ugh

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4 minutes ago, CoastalWx said:

Tossed

Do you really think we see dewpoints in the 63-65F range? There is model support for it but I am struggling to find any evidence that happens. I can see 61-62 happening. 

Also, I see some on social media going sounding happy and this is something I've noticed and not sure if there is some type of issue with generating soundings but some of the soundings (SHARPpy) people are tossing around have rather high lapse rates and dewpoints and thus throwing out some big CAPE values.

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Mentioned this yesterday in the May thread that it would/should not be surprising if SPC upgraded what was then hashed out MRGL ( to SLGHT ) for our area. 

Has the hallmarks ... A warm frontal passage wedges warm sector into the region circa 12 to 15z  ...  After associated early showers and an elevated thunder clap or two freshens up the llv theta-e ...the sun burst through and the south facing windows brighten up suddenly mid morning.  Temp bounces 14.8F in a half hour. By early afternoon blue tinted facades of the distant hill tops, along with the mash up smell of summer theta-e with early biomist turns into tropopausal rollers. 

The day of Monson Massacre did that... 

June 1986 drecho down Rt 2 did that...

Worcester 1953 did that...

From my personal logging, that seems to be a good way to get it done in NE.  Have the day dawn fighting a warm boundary, said boundary wins by 10 am... Clearing peels open a rich warm primed air mass and sun does the rest ahead of some synoptic forcing later in the day ...

None of those in that list above are intended as outright analogs ... but the orbital perspective of a warm wedge followed by evacuating S/W later in the day does bear at least a conceptual similarity.  

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2 minutes ago, dendrite said:

3k NAM is close to warm sectoring here. It'll probably be relegated to Cheshire/Hillsborough counties though.

Congrats Mitch

NAMNSTNE_con_stp_035.png

SW VT/extreme NW MA could be a really good spot for something but I think the best ingredients are going to go to waste...don't see much of a trigger to generate convection during the afternoon...or at least enough support for deep enough convection to utilize the dynamics aloft. Going to be ugly on the cold side of the front...rain and 50's...yuck

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2 minutes ago, radarman said:

3km nammy does a pretty good job of suppressing action out ahead of the front as Wiz mentioned for lack of a trigger.  Weak height rises during the course of the entire day.  Granted it does get fairly unstable. 

I wonder if the instability is overdone. Soundings from the 3km NAM show pretty steep mid-level lapse rates which may be overdone. 

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