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Severe threat today (5/3/11) central/eastern PA/NW NJ


weatherwiz

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A fairly strong cold front and positively tilted trough will be slowly working eastward throughout the morning/afternoon hours of Tuesday. Out ahead of it a warm front is expected to slowly lift northward through the region. Once the warm front passes and the area gets into the warm sector dewpoints will begin to increase as a southerly flow advects moisture northward from the south. Dewpoints are modeled to reach at least the lower 60's. This coupled with WAA in the lower levels of the atmosphere (925mb temps reaching +17C to +20C and 850mb temps reaching about +12C) and strong surface heating (temps reaching the upper 70's to perhaps lower 80's) should yield to a decent amount of surface-based instability.

Models are showing as much as 1000-2000 J/KG of SB/MUcape and MLcape values in the 1000-1500 J/KG with LI values of around -4C...if the level of heating is correct this should come to fruition. The one thing hindering a more robust instability setup is somewhat meager MLlapse rates, right now they are modeled to be around 6 C/KM or so, perhaps a bit closer to 6.5 C/KM...somewhat warmer mid-level temps and lack of temp change with height and killers here, however, there is small possibility ML lapse rates are closer to 6.5 C/KM...perhaps a bit stronger which could really help out with some stronger instability values.

As the front and stronger lift work eastward throughout the day jet dynamics increase as well, with the warm front just off to the north and sfc low just to the west the low-level wind field may back a bit thus increasing low-level helicity.

There should be storms around tomorrow, some even becoming severe, especially if there is a good deal of instability that develops. Damaging winds would be the main threat with large hail also possible...a few isolated brief tornadoes could also be possible, especially if there is a greater deal of instability that develops to go along with the backing of the low-level wind fields.

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12z SPC WRF sped up the timing by almost 4 hours. Line crosses Philly around 02z instead of 06z as it had previously.

Has mostly garden-variety stuff down here but a stronger line pushing through the Pocs and LV, which agrees with the 14z HRRR on where the best instability will be.

Really I'm not too excited about the potential. I think Central PA will get some good stuff but the timing isn't right for us farther east imo.

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12z SPC WRF sped up the timing by almost 4 hours. Line crosses Philly around 02z instead of 06z as it had previously.

Has mostly garden-variety stuff down here but a stronger line pushing through the Pocs and LV, which agrees with the 14z HRRR on where the best instability will be.

Really I'm not too excited about the potential. I think Central PA will get some good stuff but the timing isn't right for us farther east imo.

Anything of a chance for me to film something or should I need not to worry?

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MESOSCALE DISCUSSION 0692 NWS STORM PREDICTION CENTER NORMAN OK 0127 PM CDT TUE MAY 03 2011 AREAS AFFECTED...CENTRAL AND ERN PA/PARTS OF S CENTRAL NY/PORTIONS OF THE MD AND ERN WV PANHANDLES CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 031827Z - 032030Z SEVERE THREAT SLOWLY INCREASING ACROSS THE DISCUSSION AREA COULD REQUIRE WW ISSUANCE. DAYTIME HEATING ALONG AND E OF THE APPALACHIAN CREST AND AHEAD OF THE ADVANCING COLD FRONT IS RESULTING IN AIRMASS DESTABILIZATION...WITH 500 TO 1000 J/KG MIXED-LAYER CAPE NOW INDICATED BY OBJECTIVE ANALYSES -- CONSISTENT WITH MODIFICATION OF MORNING RAOBS AND THE RECENT RAOB FROM IAD /DULLES AIRPORT/. SOME CUMULUS INCREASE IS EVIDENT...WITH A SHOWER NOW OBSERVED IN BEDFORD CO. PA -- AND EXPECT A CONTINUED RAMP-UP IN CONVECTION OVER THE NEXT COUPLE OF HOURS. WITH MODERATELY STRONG FLOW ALOFT AND WEAK VEERING WITH HEIGHT...SHEAR IS SUPPORTIVE OF ORGANIZED/ROTATING STORMS. THIS COMBINED WITH THE ONGOING DESTABILIZATION SUGGESTS THAT A WW MAY BE NEEDED IN THE NEXT HOUR OR SO -- WITH CONTINUED INCREASE IN SEVERE THREAT INCLUDING POTENTIAL FOR AN ISOLATED TORNADO. ..GOSS.. 05/03/2011 ATTN...WFO...OKX...ALY...PHI...BGM...CTP...LWX... LAT...LON 39257674 39347817 40067861 41397733 42437553 42487456

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BULLETIN - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH OUTLINE UPDATE FOR WS 263

NWS STORM PREDICTION CENTER NORMAN OK

350 PM EDT TUE MAY 3 2011

SEVERE THUNDERSTORM WATCH 263 IS IN EFFECT UNTIL 1000 PM EDT

FOR THE FOLLOWING LOCATIONS

MDC001-043-040200-

/O.NEW.KWNS.SV.A.0263.110503T1950Z-110504T0200Z/

MD

. MARYLAND COUNTIES INCLUDED ARE

ALLEGANY WASHINGTON

PAC001-009-011-015-025-027-035-037-041-043-055-057-061-067-069-

071-075-077-079-081-087-089-093-095-097-099-103-107-109-113-115-

117-119-127-131-133-040200-

/O.NEW.KWNS.SV.A.0263.110503T1950Z-110504T0200Z/

PA

. PENNSYLVANIA COUNTIES INCLUDED ARE

ADAMS BEDFORD BERKS

BRADFORD CARBON CENTRE

CLINTON COLUMBIA CUMBERLAND

DAUPHIN FRANKLIN FULTON

HUNTINGDON JUNIATA LACKAWANNA

LANCASTER LEBANON LEHIGH

LUZERNE LYCOMING MIFFLIN

MONROE MONTOUR NORTHAMPTON

NORTHUMBERLAND PERRY PIKE

SCHUYLKILL SNYDER SULLIVAN

SUSQUEHANNA TIOGA UNION

WAYNE WYOMING YORK

VAC043-069-840-040200-

/O.NEW.KWNS.SV.A.0263.110503T1950Z-110504T0200Z/

VA

. VIRGINIA COUNTIES INCLUDED ARE

CLARKE FREDERICK

VIRGINIA INDEPENDENT CITIES INCLUDED ARE

WINCHESTER

WVC003-027-037-057-065-040200-

/O.NEW.KWNS.SV.A.0263.110503T1950Z-110504T0200Z/

WV

. WEST VIRGINIA COUNTIES INCLUDED ARE

BERKELEY HAMPSHIRE JEFFERSON

MINERAL MORGAN

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Not gonna happen south of say, Reading. Nice line about to move into the LV and Poconos though. Some broad rotation in the northern end of the line also. Enjoy it guys.

Very, very heavy rain.

That line slid just to my north. All I got was a passing rain shower. It was heavy for about 3 minutes.

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That line slid just to my north. All I got was a passing rain shower. It was heavy for about 3 minutes.

Sounds like there was some pretty good wind up your way though.

0030UNK 2 SW TAMAQUA SCHUYLKILL PA40787596BARN COLLAPSED 40 CATTLE TRAPPED 5 PINE TREES ACROSS ROAD (CTP

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