Active severe wx day possible on Wednesday across parts of PA/NY

[weatherwiz]

The month of April has been near historic levels as far as severe thunderstorm/tornado activity has been concerned for portions of the country as we have been in a highly volatile weather pattern this month. This pattern shows no signs of breaking down anytime soon and it appears we may include a bit more of the country into the threat for severe weather and even tornadoes. As we move towards the middle half of the week the threat for severe weather looks to extend into portions of the Northeast and portions of PA/NY may be under the gun this time.

A rather potent storm system is moving through the Plains and looks to wreck major havoc across much of the central/eastern US as a great deal of instability coupled with high amounts of moisture and strong dynamics set the stage for multiple/consecutive days of severe weather outbreaks.

Over the next few days a warm front will continue to lift northward through portions of the Northeast. This front is expected to lift enough to the north to where all of PA and a good chunk of NY is engulfed in the warm sector. Within this broad warm sector dewpoints will soar into the 60's and low-level temperatures will vastly warm as well. 925mb temps should be around +15C and 850mb temps in the +10 to +13C range. With good mixing and quality sfc heating temperatures would have the potential to reach into the lower to near mid 80's. Cloud cover from convective debris may limit this from occurring but temps should reach the mid to upper 70's nonetheless.

Just off to the west/southwest of the region a very strong and deepening sfc low will be working northeastward. This will be the sfc-low responsible for swinging the warm front northward. This low will be deepening rapidly as it approaches the area meaning there will be a good deal of height falls across the region. The deepening of the sfc low will also work to increase the dynamics aloft.

While the 0z models weren't overly impressive with the degree of instability the 3z SPC SREF beefed things up big time and given the degree of dynamics/lift/support aloft if sufficient instability can develop it could be a very active day. The 3z SPC SREF really hits SE PA area as the threat zone right now:

The 3z SPC SREF now is indicating as much as 1500-2000 J/KG of SBcape may develop with 1000-1500 J/KG of MLcape to go along with LI values around -4C.

One issue to contend with though is the system becomes somewhat wrapped up, this will cause some warming aloft in the mid-levels and slow down any cooling aloft with the eastward advancing cold front/upper level trough. This means mid-level lapse rates may be fairly weak which could really limit the degree of destabilization that occurs as well as hindering updraft strength.

The 3z SPC SREF is also indicating as much as 50 knots of vertical shear to go along with 150-200 m2s2 of 0-1km helicity and 250-350 m2s2 of 0-3km helicity. This would be more than sufficient to produce organized convection and even the potential for supercells. Again though, the degree of instability is going to be key here.

If dewpoints can indeed get into the mid 60's that would really help with drawing some of the higher instability values, especially if enough sun can occur to get temperatures to jump into the 70's.

The potential does exist for thunderstorms, some strong to severe both today and tomorrow but Wednesday has potential to be the bigger of the days depending on the degree of instability.

[weatherwiz]

The SPC already does have the entire area under a slight risk for Wednesday:

ALONG WITH FAIRLY SUBSTANTIAL SEVERE POTENTIAL EXTENDING FARTHER NNEWD INTO PA/NY -- INCLUDING THREATS FOR DAMAGING WINDS AND ISOLATED TORNADOES...SEVERE STORMS WILL LIKELY ALSO EXTEND E OF THE APPALACHIANS INTO THE ATLANTIC COAST STATES. ALONG WITH THE LIKELIHOOD FOR AFTERNOON SEVERE CONVECTION...SEVERE CONVECTION MAY CONTINUE INTO THE OVERNIGHT HOURS AS THE SURFACE FRONT CRESTS THE APPALACHIANS.

It's interesting to note this was made before the SPC 3z SREF was available (unless of course they have the data available before the public) but this run definitely beefed things up from previous runs. It will be interesting to see what the 12z guidance suggests.

[Chrisrotary12]

Wow. Eastern and southeastern PA on Wed look like they could possibly get in on some fun. Areas just north of Philly as of now look like a target area.

[PennMan]

Thanks for the input, Paul. Hoping to see something of interest here in State College.

[Tornado Girl]

You're right, we have a shot....I was talking to Andy about the set-up this morning. He and I agree that all our ducks have to be in a row this time of year. The good thing this time is we will have some instability. The last few events were nil. So with the elevated instability during the overnight and for tomorrow. Western NYS along with Western Oneida, Lewis, Oswego, and Jefferson counties have a shot at strong to severe....The instability looks even better Wednesday so the severe threat looks good for that day, as long as convection to our SW doesn't steal the show. Thursday looks good for SE NYS. Time will tell....It's almost impossible to get severe weather in April in the NE. Mid May to Mid June is normally our time....But we have had severe wx in April before so we can hope.

[Tornado Girl]

Out west it will be interesting to watch the storms develop along the dry line and cold front this afternoon.

[weatherwiz]

The best chance of anything happening would likely be across PA, PA is much more susceptible to severe this time of year than NY is. PA has had over 60 tornadoes in April which isn't too bad. The SPC SREF continues to indicate central/eastern PA as the potential hot spot area. Were really going to need to see a good deal of solar heating though to really aid in destabilizing the lower levels of the atmosphere and steepening those low-level lapse rates.

[Tornado Girl]

The best chance of anything happening would likely be across PA, PA is much more susceptible to severe this time of year than NY is. PA has had over 60 tornadoes in April which isn't too bad. The SPC SREF continues to indicate central/eastern PA as the potential hot spot area. Were really going to need to see a good deal of solar heating though to really aid in destabilizing the lower levels of the atmosphere and steepening those low-level lapse rates.

I agree....Ohio, PA, and SE NYS have the best shot.

[hudsonvalley21]

I agree....Ohio, PA, and SE NYS have the best shot.

Mt. Holly is thinking on the bullish side for Thursday. A section of their AFD

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE MOUNT HOLLY NJ

756 PM EDT MON APR 25 2011

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...

TUESDAY-WEDNESDAY...USED MAINLY THE PRIOR 4AM KPHI FCST TEMPS WHICH

ARE WARMER BOTH DAY AND NIGHT THAN THE 12Z/25 NCEP GUIDANCE WHICH

MAY STILL BE PARTIALLY BIASED COOLER TO CLIMO.

THIS EARLY SUMMER AIRMASS SHOULD BE ESSENTIALLY RAIN FREE UNTIL THE

CFP THURSDAY. WE HAVE POPS IN THE FCST IN DEFERENCE TO GUIDANCE.

ALSO A SHORT WAVE MOVING NEWD OFF THE SE COAST OF THE USA MAY PRODUCE

SHOWERS TUE NIGHT OR WED MORNING AND OF COURSE...REMNANT W OF THE

APPALACHIANS TSTM ACTIVITY MAY AT TIMES GRAZE OR REFIRE ALONG THE

W FRINGE OF OUR FA.

SKYCOVER FOR OUR AREA ON WEDNESDAY MAY BE TOO HEAVY AND ITS A LOW

CONFIDENCE FCST. BELIEVE THE 12Z NCEP GFS/NAM TSECS ARE TOO HEAVY

ON THE BL MOISTURE AND THEREFORE OFFER TOO MUCH CLOUD COVER.

GUSTY SSW WINDS TO 25 KTS EXPECTED ON THE LAND TUE AND WED AFTNS.

THURSDAY...COULD BE OUR SVR WX DAY WITH A STRONG UNSTABLE LLJ AND

OBVIOUSLY EXCELLENT SHEAR....ENOUGH FOR ISOLATED TORNADO PRODUCTION

IF THE MODELED INSTABILITY PANS OUT AHD OF THE CFP.

FOR NOW...THE FCST HAS THUNDER AND R+. WE CAN ADD GUSTY WINDS IN

FUTURE FCST CYCLES IF CONFIDENCE INCREASES. HWO WILL FOCUS ON A

SVR WX EVENT POTENTIAL FOR THURSDAY...ESPECIALLY MORNING/MIDDAY.

[weatherwiz]

If enough instability does develop I could certainly see a threat for isoalted tornadoes across eastern PA and perhaps NW NJ...this is hwere it appears the strongest instability will occur plus the low-level wind flow will be more backed across this area. Shear is going to be pretty strong though and with weak ML lapse rates were going to need to see a good deal of sfc heating/upper level support for vigorous enough updrafts to develop and be sustained.

[hudsonvalley21]

If enough instability does develop I could certainly see a threat for isoalted tornadoes across eastern PA and perhaps NW NJ...this is hwere it appears the strongest instability will occur plus the low-level wind flow will be more backed across this area. Shear is going to be pretty strong though and with weak ML lapse rates were going to need to see a good deal of sfc heating/upper level support for vigorous enough updrafts to develop and be sustained.

It will be interisting to see what happens. I work out in eastern Pa. in the Lehigh valley region near Nazareth. I will post my obs. and keep you all updated. We'll see what the next few runs put out. The fun season is here Paul, any toughts of a chase this week ?

[weatherwiz]

It will be interisting to see what happens. I work out in eastern Pa. in the Lehigh valley region near Nazareth. I will post my obs. and keep you all updated. We'll see what the next few runs put out. The fun season is here Paul, any toughts of a chase this week ?

I won't be going chasing this week, I have baseball too on Wednesday so will probably miss out on most of the afternoon unfortunately. I'll be doing some local chasing though the first two weeks of June when my friend from NH comes down.

Even if this event doesn't pan out though I think as we move into May and the first few weeks of June we'll see some pretty good potential, especially across PA/NY. This pattern is probably not going to be going anywhere anytime soon, at least until the heat ridge builds in...if it even does so.

[hudsonvalley21]

I won't be going chasing this week, I have baseball too on Wednesday so will probably miss out on most of the afternoon unfortunately. I'll be doing some local chasing though the first two weeks of June when my friend from NH comes down.

Even if this event doesn't pan out though I think as we move into May and the first few weeks of June we'll see some pretty good potential, especially across PA/NY. This pattern is probably not going to be going anywhere anytime soon, at least until the heat ridge builds in...if it even does so.

Agree, It will be interesting the next month or so. As long as your chasing the cells instead of them chasing you, all is good. Good luck on Wednesday.

[weatherwiz]

Agree, It will be interesting the next month or so. As long as your chasing the cells instead of them chasing you, all is good. Good luck on Wednesday.

Wednesday is an alright setup, it's not one that is going to produce a widespread severe wx outbreak but there could be a small localized area that gets hit pretty good. Damaging winds are going to be the main threat.

Being a few days out it's really to gauge any tornadic potential, although looking at things right now that threat does exist but we'll see what happens as we get closer to Wednesday.

[weatherwiz]

Looking at the 0z NAM so far the eastward progression of the front continues to slow down...I wonder if perhaps Thursday might be the day, on Wednesday aloft there is a good deal of ridging still which will mean sucks lapse rates, on Thursday though we get some height falls aloft as the front/trough move closer to the area.

[Tornado Girl]

Arkansas will be hit hard again tomorrow. LLJ will help the SBCAPE values into the 300 to 600 J/Kg overnight. As for tomorrow and Wednesday CAPES should be in the 600- 1400 J/Kg range....As for severe Wx for tomorrow, it will depend on how fast we lose the debris clouds from the overnight and early morning hours; also, if we see that trigger the models are showing pulls thru tomorrow afternoon. Thursday could be a good day for NE PA and SE NYS depending on how much instability we actually see.

[weatherwiz]

Yeah we can look at the models all we want for this area Wednesday/Thursday but unfortunately this is all going to depend on how much instability can develop and as we know living in this area that's not an easy task. Going to be one of those nowcast situations where you look out the window when you wake up then look at satellite trends.

The one key thing to keep in mind is the bulk of the moisture/clouds is going to be low-level, there will be a decent amount of dry air in the mid-levels which could really help to mix out some of this low-level moisture/clouds much faster than what models are showing.

[Tornado Girl]

Yeah we can look at the models all we want for this area Wednesday/Thursday but unfortunately this is all going to depend on how much instability can develop and as we know living in this area that's not an easy task. Going to be one of those nowcast situations where you look out the window when you wake up then look at satellite trends.

The one key thing to keep in mind is the bulk of the moisture/clouds is going to be low-level, there will be a decent amount of dry air in the mid-levels which could really help to mix out some of this low-level moisture/clouds much faster than what models are showing.

I agree all good points...I only mention the models because they show an afternoon trigger.......There will be a lot of shear....but the Capes won't be all that impressive. If the shortwave pulls thru and the timing works out just right.... we might see something.

[weatherwiz]

I agree all good points...I only mention the models because they show an afternoon trigger.......There will be a lot of shear....but the Capes won't be all that impressive. If the shortwave pulls thru and the timing works out just right.... we might see something.

Yup good point...didn't mean not to look at the models at all...meant they are just going to handle the instability situation poorly

Yeah the trigger is something to watch b/c if some weak instability can develop given the shear it could be enough for some isolated action.

[weatherwiz]

New Day 2 has much of western PA in the 30% risk zone...I'm real interested to see what the new day 3 says. I'm tempted to stay up for it but I have to work at 11:00 AM and I've only slept 2 hours over the past 2 days. I might just go to sleep now and wake up around 4 AM...the 3z SPC SREF should also be coming out around then as well...or sometime between 4-5 AM.

[weatherwiz]

Very favorable thermodynamic environment setting up across parts of NY/PA...strong sfc heating coupled with steep ML lapse rates setting the stage for some decent instability. Dynamics aloft are quite strong too. Damaging winds/large hail are the main threats, while an isolated tornado is possible due to the fairly high/increasing helicity values LCL's are a little on the high side.

[weatherman5416]

New Day 2 outlook has Western PA in the hatched Moderate Risk area.

[weatherwiz]

If enough instability can develop tomorrow...which is certainly possible b/c the column is dry enough to where sfc heating is being underforecasted but if enough instability can develop tomorrow could certainly be active...if it does become apparent that sfc heating is underdone I could see the mod risk being expanded further into PA.

The question then is what is the main threat for tomorrow? Will the tornado threat be on the isolated side or where there be a distinct threat for tornadoes? This will all depend on the storm mode tomorrow and how things align.

[2Slick]

HOLY CRAP!

What an awesome storm. Strong winds, great lightning streaks, insanely loud thunder. 1.75" hail reported in Syracuse! My street is practically impassible.

I love severe storms.

[NorEaster27]

my brother in syracuse is reporting roads are flooded and closed.

[Tornado Girl]

Confirmed tornado on the ground near Rome, NY

[2Slick]

my brother in syracuse is reporting roads are flooded and closed.

Yeah, never seen it like this before.

[Tornado Girl]

That super cell in Central Oneida County is a right hand turner.

[2Slick]

CRAZY pictures from east side of Syracuse:

http://plixi.com/p/96223296

http://plixi.com/p/96220232

[2Slick]

Another storm heading our way. GOLF BALL size hail...heads up haha!