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Central PA - December 2017


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3 hours ago, Wmsptwx said:

Severe possible tomorrow, any mets have thoughts?

Its an shocker, i guess the Mets are out and about. But from the looks what i am seeing and models, Day 3 Marginal, Day 2 Slight, then 2nd Day 2 went to Enhanced, will not be shocked based on upcoming runs that an moderate could be need either at the 2AM Day 1 or and later outlook.  Very small area in West and Central PA up to Western NY. Looks like localized outbreak type day with mix of wind damage, large hail, and tornadoes

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4 hours ago, Wmsptwx said:

Severe possible tomorrow, any mets have thoughts?

There's certainly a good amount of low-level moisture in the western half of PA with dew points in the low to mid 60s. Deep layer shear looks pretty impressive for tomorrow as well as some curvy 0-3 km hodographs. I think the biggest issue (per usual in the northeast) will be whether sufficient instability will be present ahead of the convection. One potential issue is how persistent the easterly flow near and east of State College will be, where low-level clouds could limit instability. You can see that there's currently a backdoor front somewhere in eastern PA with temperatures in the low 60s to low 50s and dew points in the 40s.

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3 minutes ago, Wmsptwx said:

 

Wow, parameters are pretty impressive for this part of the country.

Mostly for entertainment, here is the 3km NAM for a point in Clearfield County Monday afternoon. Always interesting to see > 500 m^2/s^2 0-1 km SRH and > 1000 J/kg CAPE in a forecast sounding. nam4km_2017043018_027_40.93--78.49.png

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Storms are going to be absolutely flying tomorrow in this area. Consensus on a 700 mb jet of 60-80 kts positioning itself over W/Central PA and W NY through the afternoon.

I can't imagine 75/66 at IDI at 02z is all that common in this region with a system of this intensity waiting to shift NE, especially with a lack of an organized MCS to the west. That corridor of backing low level flow showing up on the higher res guidance is certainly intriguing with the strength of the H925-H85 flow being forecast.

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Saussman, good morning! I'm not crazy with potential of high end severe, but certainly some opportunity for interesting weather later today. Clouds are thinning here and over most of CPA, but not Sure we acquire instability necessary for high end severe. That being said, most other parameters are very favorable for severe.

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Some breaks in the stratocumulus here to the east but not much sun so far. We'll need pretty substantial surface heating to realize any discrete supercells later on, as the mid-level lapse rates are not that impressive on the 12z soundings from PIT and IAD. Most guidance is pretty optimistic for a QLCS during the early evening in central PA with strong forcing ahead of the cold front, and we could see some strong gusts with 60+ kt 850 mb winds mixing down.

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2 minutes ago, heavy_wx said:

Some breaks in the stratocumulus here to the east but not much sun so far. We'll need pretty substantial surface heating to realize any discrete supercells later on, as the mid-level lapse rates are not that impressive on the 12z soundings from PIT and IAD. Most guidance is pretty optimistic for a QLCS during the early evening in central PA with strong forcing ahead of the cold front, and we could see some strong gusts with 60+ kt 850 mb winds mixing down.

What does SPC see that has them so bullish on TOR odds over large area?

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42 minutes ago, Wmsptwx said:

Saussman, good morning! I'm not crazy with potential of high end severe, but certainly some opportunity for interesting weather later today. Clouds are thinning here and over most of CPA, but not Sure we acquire instability necessary for high end severe. That being said, most other parameters are very favorable for severe.

that was my line of thinking as well. Its not clearing that fast here but who knows. I did send out a quick brief to our fire officers this morning so they keep an eye on it. 

 

Edit- i'm not overly concerned about tornadoes, But i know how the wind gets around my area with these types of events. 

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Quite the interesting setup later this afternoon.  Bufkit forecast soundings are quite impressive with very large hodographs thanks to very strong speed shear and presence of low-level directional shear.  Should be some great forcing as well thanks to decent height falls and potent mid-level jet streak pushing into the region.  While instability won't be the greatest, the degree of forcing and jet dynamics should compensate a bit.  Some flags, however, are the lack of steeper mid-level lapse rates which will work to hold instability back a bit, storm mode looks to become linear rather quickly which could inhibit tornado potential, LCL's look on the higher side which could further hurt tornado potential as well.  But like heavy_wx said, given the parameters QLCS tornadoes are certainly possible in this type of environment.  I wonder if the hail aspect of this is being underplayed.  Bufkit soundings are showing between 400-500 J/KG of hail cape across PA which is pretty impressive...especially considering the degree of helicity.  I think though we should see a rather impressive squall line develop and given degree of low-level winds probably see quite a few damaging wind gusts.  

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Given degree of dynamics full sun isn't entirely a necessity, however, it certainly would help...especially if you're looking for a more widespread outbreak potential but given degree of dynamics and forcing several hundred J of cape I think should more than suffice.  Just need enough buoyancy for updrafts to be able to be strong enough to utilize the shear aloft and not topple over.

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7 minutes ago, canderson said:

Meso out for PIT and enviros. I think the heavy stuff stays NW of the lower valley.

A friend (well an acquaintance, hadn't talked for a few years) was killed in the Saturday night tornado in East Texas, hope all you guys keep safe this evening.

Sorry to hear that man, this stuff is only fun when all are safe. 

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41 minutes ago, canderson said:

Meso out for PIT and enviros. I think the heavy stuff stays NW of the lower valley.

A friend (well an acquaintance, hadn't talked for a few years) was killed in the Saturday night tornado in East Texas, hope all you guys keep safe this evening.

sorry to hear :(

ditto...this is only fun when everyone is safe 

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