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Central PA Late Spring 2012


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anyone else see this?

day3otlk_0730.gif

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0230 AM CDT WED MAY 30 2012

VALID 011200Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE EASTERN

STATES...

...MUCH OF THE EASTERN STATES...

SEVERE POTENTIAL THE FIRST DAY OF JUNE WILL GENERALLY BE TIED TO THE

EAST-NORTHEASTWARD ADVANCEMENT OF A POTENT UPPER TROUGH OVER THE

EASTERN THIRD OF THE CONUS...FOCUSED ALONG/AHEAD OF AN EASTWARD

MOVING COLD FRONT. SOME TIMING/SPATIAL UNCERTAINTIES CARRYOVER FROM

THE DAY 2 PERIOD...WITH 00Z ECMWF/NAM GUIDANCE GENERALLY FASTER THAN

THE 00Z GFS. NEVERTHELESS...AS THE PARENT UPPER SYSTEM TRENDS TOWARD

A SLIGHT NEGATIVE TILT ON FRIDAY...AMPLE FORCING FOR ASCENT/VERTICAL

SHEAR WILL CONTRIBUTE TO SUSTAINED STRONG/SEVERE TSTMS WITHIN A

DIURNALLY DESTABILIZING BOUNDARY LAYER...WITH THE POSSIBILITY OF

1000-2000 J/KG MLCAPE. THIS WILL BE THE CASE 1/ AHEAD OF THE COLD

FRONT AND 2/ ALONG AND SOUTH OF A NORTHWARD-SHIFTING WARM FRONT

ACROSS THE MID-ATLANTIC STATES/DELMARVA.

DAMAGING WINDS /POTENTIALLY WIDESPREAD/ AND SEVERE HAIL WILL BE THE

PRIMARY HAZARDS FROM WHAT SHOULD MAINLY BE A MULTICELLULAR/LINEAR

CONVECTIVE MODE. SOME SUPERCELLS...PERHAPS EVEN A TORNADO

THREAT...COULD OCCUR PROVIDED SUFFICIENT DESTABILIZATION NEAR THE

AFOREMENTIONED WARM FRONT. FARTHER SOUTH...A MORE ISOLATED/MARGINAL

SEVERE POTENTIAL IS ANTICIPATED ACROSS THE SOUTHEAST STATES/FL.

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I am in Enola (just northwest of harrisburg)... major flash flooding here right now.... had some scattered 1" hailstones a little while ago... bucket on my back deck is currently at 4" and rising.... my natural stream out back is currently a raging river... its coming down so hard i am having trouble getting pictures and video but will post anything i can when (if) it lets up

you should have come around the corner to my house, you could have stood in my garage with us, having a beer and watching. Big time flash flooding in our area (Enola/Summerdale) A guy from the fire house walked over and showed me pictures he took, it looked like a river running down the streets. My rain gauge broke and i haven't replaced it yet, so i have no idea what the total was.

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12z NAM and GFS runs both make Friday evening interesting... the way they currently are SPC would have to pull that risk area northward... track of low and when the tilt occurs for both runs have central to east PA in the hotspot (in addition to tapping into a +1-2 standard deviation precipitable water anomaly)

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day2probotlk_0600_any.gif

...MUCH OF THE EASTERN STATES...

THE FIRST DAY OF JUNE WILL SEE THE EAST-NORTHEASTWARD ADVANCEMENT OF

A POTENT UPPER TROUGH OVER THE EASTERN THIRD OF THE CONUS...WITH

DEEP CONVECTIVE/SEVERE POTENTIAL FOCUSED ALONG/AHEAD OF AN EASTWARD

MOVING COLD FRONT AS IT CROSSES THE APPALACHIANS FRIDAY

MORNING/AFTERNOON. THE PARENT SYSTEM IS EXPECTED TO SLOWLY TREND

TOWARD A SLIGHT NEGATIVE TILT ON FRIDAY...WITH A STEADILY

STRENGTHENING BELT OF DEEP LAYER SOUTHWESTERLY FLOW OVERSPREADING

MUCH OF THE CENTRAL APPALACHIANS AND MID-ATLANTIC/NORTHEAST STATES.

ACCORDINGLY...AMPLE FORCING FOR ASCENT/VERTICAL SHEAR WILL

CONTRIBUTE TO SUSTAINED STRONG/SEVERE TSTMS WITHIN A DIURNALLY

DESTABILIZING BOUNDARY LAYER...WITH SUCH DEVELOPMENT FOCUSED IN

VICINITY OF THE COLD FRONT OR PERHAPS A PRE-FRONTAL TROUGH. IT IS

LIKELY THAT AMPLE PRE-FRONTAL INSOLATION WILL COINCIDE WITH AN

INCREASINGLY MOIST BOUNDARY LAYER...SUCH THAT A BROAD AREA OF

1000-2000 J/KG MLCAPE SEEMS LIKELY FROM THE CAROLINAS TO THE

DELMARVA/SOUTHERN PA...ALONG/SOUTH OF A NORTHWARD-SHIFTING WARM

FRONT ACROSS THE MID-ATLANTIC STATES/DELMARVA. THAT SAID...LOCALLY

STRONGER DESTABILIZATION WILL BE POSSIBLE ACROSS PARTS OF THE

CAROLINAS/GA/NORTH FL ALBEIT WITHIN A WEAKER SHEAR REGIME.

OVERALL...DAMAGING WINDS /POTENTIALLY WIDESPREAD AT THAT/ AND SEVERE

HAIL WILL BE THE PRIMARY HAZARDS FROM WHAT SHOULD MAINLY BE A

MULTICELLULAR/LINEAR CONVECTIVE MODE ACROSS THE MAJORITY OF THE

SLIGHT RISK AREA. THAT SAID...SOME SUPERCELLS...INCLUDING A TORNADO

THREAT...COULD OCCUR MAINLY ACROSS VA/DELMARVA REGION INTO SOUTHERN

PA/NJ PROVIDED 1/ SUFFICIENT DESTABILIZATION OCCURS NEAR THE WARM

FRONT AND 2/ SEMI-DISCRETE DEVELOPMENT OCCURS AHEAD OF THE COLD

FRONT WHERE A LINEAR MODE SHOULD BE MORE DOMINANT. SOMEWHAT HIGHER

PROBABILITIES/PERHAPS EVEN A CATEGORICAL MODERATE RISK MIGHT BE

WARRANTED IN SUBSEQUENT CONVECTIVE OUTLOOKS.

Hazardous Weather Outlook

HAZARDOUS WEATHER OUTLOOK

NATIONAL WEATHER SERVICE STATE COLLEGE PA

241 AM EDT THU MAY 31 2012

PAZ035-036-056-057-059-063>066-010645-

FULTON-FRANKLIN-PERRY-DAUPHIN-LEBANON-CUMBERLAND-ADAMS-YORK-

LANCASTER-

241 AM EDT THU MAY 31 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY AND TONIGHT.

HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FRIDAY AFTERNOON

AND EVENING. STORMS WILL LIKELY CONTAIN HEAVY DOWNPOURS WITH

INTENSE RAINFALL RATES...POSSIBLY RESULTING IN LOCALIZED FLOODING.

DAMAGING WINDS AND LARGE HAIL WILL BE THE PRIMARY SEVERE THUNDERSTORM

HAZARDS. HOWEVER...THERE WILL BE AN ELEVATED CONDITIONAL THREAT

FOR ISOLATED TORNADOES.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS LIKELY ON FRIDAY AFTERNOON AND EVENING.

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Dr Forbes posted his initial TORCON forecast for Friday:

Friday, June 1

AL south - 2

DC - 4

DE - 4

FL panhandle - 2

GA east-central, south - 2

MD east - 4

MD central - 2 to 3

NC central, east - 2

NJ north - 2

NJ south - 3

PA southeast - 4

SC central, east - 2

VA north - 4

VA south-central, east - 2 to 3

Other areas - 1 or less

a 4 or higher in PA does not happen often at all

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Quite an interesting couple days ahead. In contrast from what we've seen with the past few severe weather episodes, speed and directional shear look excellent. But i'm worried about how far north we can get this warm front to come. Whether it stays in Maryland, or moves up into southern PA will make a huge difference in the northward extent of severe storms. Hard to pinpoint right now, but something to keep an eye on in future model runs this evening.

Here are the SREF plumes for instability at UNV...

345l9a0.jpg

Cloud cover is another concern. I think we should see enough breaks in the clouds to destabilize southern PA enough (1000 J/kg CAPE?), but this is yet another thing to keep an eye on tonight and tomorrow morning. Some of the higher resolution models are suggesting that we could get some discrete cells forming ahead of the main line in the vicinity of the warm front. This could be enough for SPC to pull the trigger for a mod risk in northern VA, central MD, and southern PA.

2euigew.jpg

6h6z9z.jpg

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Latest from SPC:

AN AREA OF STRONG HEIGHT FALLS...ON THE ORDER OF 60-90M...WILL

OVERSPREAD THE OH VALLEY DURING THE DAY FRIDAY AS SLIGHTLY NEGATIVE

TILTED UPPER TROUGH AXIS PROGRESSES TO A POSITION FROM LOWER

MI...ARCING SEWD TO SC BY 02/00Z. AN EXPANSIVE AREA OF LARGE SCALE

ASCENT IS EXPECTED TO OVERSPREAD THE REGION AHEAD OF THIS UPPER

DIFFLUENT TROUGH AND SHOULD PROVE SUPPORTIVE OF WIDESPREAD

CONVECTION ALONG ADVANCING COLD FRONT AS IT SURGES EWD.

THUNDERSTORMS SHOULD BE ONGOING EARLY IN THE PERIOD ALONG THE COLD

FRONT FROM OH...SWD INTO NRN GA. WHILE STRONG SHEAR WILL COINCIDE

WITH THIS ACTIVITY IN ALL LIKELIHOOD BROKEN LINEAR TSTM SEGMENTS

SHOULD BE MOSTLY NON-SEVERE...OR PERHAPS MARGINALLY SEVERE AT

DAYBREAK. MAIN LIMITING FACTOR FOR SEVERE EARLY IN THE PERIOD WILL

BE DUE TO MEAGER INSTABILITY. HOWEVER...BOUNDARY LAYER HEATING

SHOULD AID IN AIR MASS DESTABILIZATION BY 18Z AND SUFFICIENT

BUOYANCY WILL DEVELOP FOR ROBUST UPDRAFTS WITHIN AN ENVIRONMENT MORE

THAN SUFFICIENTLY SHEARED FOR ORGANIZATION. IN FACT...FORECAST

SOUNDINGS SUGGEST ROTATING UPDRAFTS/SUPERCELL STRUCTURES ARE

POSSIBLE. GIVEN THE AFOREMENTIONED LARGE SCALE SUPPORT...IT APPEARS

A STRONGLY FORCED SQUALL LINE SHOULD BE NOTED WITH ADVANCING COLD

FRONT AND GRADUAL INTENSIFICATION IS EXPECTED AS AIR MASS

DESTABILIZES...PRIMARILY EAST OF THE APPALACHIANS AND WITH TIME

ACROSS PORTIONS OF PA. DAMAGING WINDS MAY BE COMMON WITH THE SQUALL

LINE...ESPECIALLY IF MUCAPE CAN EXCEED 1500 J/KG AS NAM SUGGESTS.

AT THIS TIME WILL MAINTAIN 30% SEVERE PROBS TO ACCOUNT FOR THE

EXPECTED STRONG WINDS WITH THE FRONTAL CONVECTION AND FOR ISOLATED

TORNADOES THAT COULD BE NOTED IF PRE-FRONTAL DISCRETE SUPERCELLS

DEVELOP. HOWEVER...THERE IS SOME CONCERN THAT A MORE WIDESPREAD

EVENT MAY EVOLVE IF LOW LEVEL LAPSE RATES/INSTABILITY RESPOND PRIOR

TO FRONTAL PASSAGE AND SEVERE PROBS MAY BE INCREASED TO ACCOUNT FOR

THIS SCENARIO IN LATER OUTLOOKS.

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My biggest "concern" if you will, for the development of widespread severe weather in this situation would be how far we can get the warm sector into PA and how much sun we manage to see tomorrow. I'd say the the lower Sus Valley obviously would be my area to really keep an eye out tomorrow, as they likely get some decent sun to ramp up CAPE's/low level lapses and take advantage of an already dynamic set up. Further south underneath southeast PA in MD and northern VA seem like they will be even more under the gun.

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Oh true, I can do that yeah. I'm sure I have a spare wood piece around here somewhere.

That's probably your best bet, as long as you can get it far enough away from buildings and trees.

On a more directly weather-related note, my aunt in Snyder County recorded 11.4" of rain in May. That area seemed to cash in on every rain and thunderstorm opportunity.

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Yeah we'll not see the major severe stuff here methinks. Gotta get down on S MD /N VA I'd guess for that. The warm front doesn't look like it'll make iypt this far north, hurting our chances.

We will see heavy rain and strong wind gusts though later.

early this morning i thought we were golden. The sun seemed like it was going to be in control, but man did it cloud up quick. I think the temp has only gone up a couple degrees since around 6. The wind is increasing though.

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