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SE PA/Mt. Holly severe threats..


NaoPos

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I'm kind of simple-minded and will get a kick even out of "plain" thunderstorms. Hopefully we can manage some of that at least. But the point-and-click is also indicating 1-2" of rain possible. Don't want to get greedy here, but that would be nice too. :whistle:

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Looked at the 12 and 18...this continues to be a MDT-LNS on south threat. Philly gets wind, some thunder, some rain...maybe severe criteria but the goods (if they go) will be in Central PA...pretty much Chambersburg to Harrisburg to Lebanon to Lancaster is the best spot in the state for anything to go.

i definitely would say pitt on east to about mdt looks the best, with the best shot around the laurels. Some good cape values and LI just east of pitt. The EHI numbers are conducive for super cell development. Only thing that could hurt them is the front may arrive just after noonish. But number wise they look the best in the state.

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18Z 4KM Nam at 22Z on Friday suggesting some discrete cells ahead of the main line. One note: there is far less morning cloudiness from the 12Z to the 18Z runs at the same times, which could be why there are more discrete cells shown.

By the time they get up to Philly on that run they weaken a bit.

DE has a shot at getting some stuff but the air may be a bit too stable for anything more than run of mill gusty winds here.

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as Indicated by some sim radars and models heavy rain fall is likely regardless of thunderstorm strength tomorrow some areas I95 North and west would not need much in a 3 hour period for flash flooding. I would suspect flash flood watches get posted overnight tonight or sometime tomorrow morning for I95 north and west into the Leigh valley.

ffg_NJ_3.gif

Also the RPM model for whatever it is worth for several runs now (updates every 3 hours) has tried to bring the warm front through Philly around 1pm. not agreeing with this model or saying this model is right but something to to watch that is for sure.

http://www.chicagoweathercenter.com/maps/rpm/

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How far east was the front supposed to be at this point? The line of convection with the front is already starting to come into Ohio, with cells ahead of it, moving NE into WV.

18z GFS had nothing this far east this soon. Interesting thing about this is when a storm in the winter is ahead of schedule it does not mean much when the same process that occurs almost every winter event happens with a thunderstorms threat it has a greater effect on storm strength. It would Fall right in line with the RPM if this continues.

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18z GFS had nothing this far east this soon. Interesting thing about this is when a storm in the winter is ahead of schedule it does not mean much when the same process that occurs almost every winter event happens with a thunderstorms threat it has a greater effect on storm strength. It would Fall right in line with the RPM if this continues.

the nam's sim radar is pretty much spot on for right now.

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SPC keeps it a SLGT, but has a large area of 10% TOR

day1probotlk_20120601_1200_torn_prt.gif

and an excellent disco from them too

...CENTRAL APPALACHIANS AND UPPER OH RIVER REGION TO MID-ATLC AND

CAROLINAS...

SCATTERED-NUMEROUS TSTMS ARE EXPECTED TO DEVELOP IN BAND NEAR OR

AHEAD OF SFC COLD FRONT BY MIDDAY...OVER WRN PORTIONS OUTLOOK

AREA...THEN MOVE NEWD WHILE BACKBUILDING SWD. NET EFFECT SHOULD BE

EWD SPREAD AND INCREASE IN BOTH CONVECTIVE COVERAGE AND SVR

POTENTIAL AS FOREGOING AIR MASS DESTABILIZES DIURNALLY. DAMAGING

GUSTS APPEAR LIKELY WITH DOMINANT QUASI-LINEAR STORM MODE...ENHANCED

LOCALLY BY TRACKS OF BOW/LEWP FORMATIONS. MANY WIND-DAMAGE EVENTS

MAY OCCUR...ALTHOUGH FCST LOW-LEVEL WIND PROFILES DO NOT YET APPEAR

STRONG ENOUGH TO SUPPORT ORGANIZED THREAT OF SIGNIFICANT GUSTS OF 65

KT OR GREATER. PATCHES OR CLUSTERS OF CONVECTION ALSO MAY BECOME

SFC-BASED DURING MIDDAY THROUGH AFTERNOON IN FOREGOING WARM

SECTOR...AMIDST STRENGTHENING DEEP-LAYER SHEAR PROFILES FAVORABLE

FOR SVR.

GREATEST RELATIVE SPATIAL OVERLAP/DENSITY OF TORNADO POTENTIAL MAY

BE FROM N-CENTRAL/NERN NC ACROSS CENTRAL VA TO CHESAPEAKE BAY

REGION. THAT CORRIDOR REPRESENTS SPATIAL OVERLAP OF THREAT FROM 1.

EARLIER/MORE DISCRETE AND DIURNAL CONVECTION...WHERE DISCRETE OR

EMBEDDED/CLUSTERED SUPERCELLS ARE POSSIBLE BUT SPECIFIC FOCI FOR

LOW-LEVEL FORCING ARE MORE NEBULOUS AND UNCERTAIN...AND

2. MORE CERTAIN ARRIVAL OF LATER AFTERNOON/EVENING QLCS ACTIVITY

CONTAINING EMBEDDED CIRCULATIONS.

FCST HODOGRAPHS...WHILE FAVORABLE IN BOTH REGIMES...DO NOT APPEAR AS

LARGE OVER BROAD AREAS AS ON MOST ERN-CONUS TORNADO OUTBREAK

DAYS...AND THERE ARE CONSIDERABLE UNCERTAINTIES ATTM REGARDING

DENSITY/LONGEVITY OF ANY SUPERCELL MODES.

EXTENT/MAGNITUDE OF WARM-SECTOR DESTABILIZATION ALSO REMAINS QUITE

UNCERTAIN ATTM...BECAUSE OF LARGE AREA OF ANTECEDENT CLOUD COVER AND

PATCHY/CLUSTERED PRECIP. THIS INDICATES DISPLACEMENT BETWEEN MOST

UNSTABLE/MOIST MARINE AIR OVER SRN/ERN CAROLINAS AND STRONGEST

VERTICAL SHEAR FARTHER N ACROSS PA/WV/MD AND NRN VA. THIS ALSO IS

MAIN FACTOR PRECLUDING GREATER SVR PROBABILITIES ATTM.

GIVEN THESE FACTORS...PROBABILITIES ARE KEPT WITHIN UPPER REACHES OF

CATEGORICAL SLGT RISK BIN FOR NOW...THOUGH UPGRADE IS POSSIBLE LATER

TODAY ONCE SOME OF THESE DESTABILIZATION AND MOISTURE FACTORS BECOME

BETTER-FOCUSED.

I'm kinda surprised at the 10% tor given their disco and the fact that they tend to be conservative with EC episodes (imo) but it certainly does look like it's game on for VA and MD.

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as Indicated by some sim radars and models heavy rain fall is likely regardless of thunderstorm strength tomorrow some areas I95 North and west would not need much in a 3 hour period for flash flooding. I would suspect flash flood watches get posted overnight tonight or sometime tomorrow morning for I95 north and west into the Leigh valley.

Also the RPM model for whatever it is worth for several runs now (updates every 3 hours) has tried to bring the warm front through Philly around 1pm. not agreeing with this model or saying this model is right but something to to watch that is for sure.

http://www.chicagowe...r.com/maps/rpm/

NYC might issue one for parts of North Jersey where the three hour guidance is just under two inches (and it would make some sense to have one up there) but the only area in the PHI CWA that might even be borderline for a FFW would be the Poconos...in a three hour window those #'s are that great if you're trying to push for a flood watch.

2.5-3" in a 3-6 hour window is not expected in this event around here. Almost all major modeling on this is under two inches in their footprint.

Mentioning heavy rain in their zones and some wording (which is in their AFD already) about possible flooding in localized spots is enough.

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Not feeling too optimistic about this evenings chances.

cfacce86-a4bb-7cd0.jpg

Keep an eye on the warm front this morning into early afternoon. Need this thing to blow by us. Still a lot of cloud cover associated with it.

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Does the current overcast and showery weather inhibit the chances of severe later today or could it offer a hint as to where the possible supercells may track?

The overcast skes now are associated with the warm front lifting north. If it stalls here, and we stay cloudy, don't expect too much in the way of thunderstorms , let alone severe. Easterly winds are not what you want. We need to Propogate into the warm sector and need the sun to come out to even think about severe storms. Another thing we have to worry about is timing. If we get warm and sunny, we have a chance of getting some heavier stuff later.

@LV, the associates cold front to the west is pretty dynamic. Just gonna be a now cast thing.

This was from HM (not accu HM).:

I agree that things get awfully interesting with the actual front and strengthening wind fields late between 00z-06z W-E (from DC to PHL). The SREF sig tor probs are certainly noteworthy in this corridor during that time frame.

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Latest RPM model run is rather interesting has a vigorous squall line with the cold front. Kind of thins out a bit when coming through our area but is still rather nasty.

http://www.chicagoweathercenter.com/maps/rpm/

Joe,

Probably because the model sees the more stable air and loss of diurnal heating.

The forcing might make up for some of lack of instability, with some shear in place.

A funny gut feeling tells me it's gonna do what Tuesday's threat as it reached Philly and fall apart. (just a feeling). Safe forecast would be for low topped convection, maybe some boomers and brief rains.

Of course, if we can get this warm felt thru, and destabilize moderately, maybe we'll have some mucape leftover, and the elevated convection is a little stronger. Not expecting much in the way of discrete stuff.

Sent from my iPad HD

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Joe,

Probably because the model sees the more stable air and loss of diurnal heating.

The forcing might make up for some of lack of instability, with some shear in place.

A funny gut feeling tells me it's gonna do what Tuesday's threat as it reached Philly and fall apart. (just a feeling). Safe forecast would be for low topped convection, maybe some boomers and brief rains.

Of course, if we can get this warm felt thru, and destabilize moderately, maybe we'll have some mucape leftover, and the elevated convection is a little stronger. Not expecting much in the way of discrete stuff.

Sent from my iPad HD

Both the RAP and the HRRR never get us above 750 J/Kg of CAPE.

The warm front has now been consistently modeled to our south, so I think it's about time we give up and just watch what happens down in the DC area.

Btw, Moderate Risk.

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15% TOR. Yikes! Can't remember ever seeing that in the Mid-Atlantic before.

Yea, pretty impressive. A small area, but very populated nonetheless. Makes me think I should have taken a ride. Buddies of mine live down in silver spring md.

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Yea, pretty impressive. A small area, but very populated nonetheless. Makes me think I should have taken a ride. Buddies of mine live down in silver spring md.

Silver Spring is a great place! You should have taken the hop down here!

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My husband and I are leaving this evening to drive to VA Beach...Looks like our timing will be close since we aren't leaving until 6:30 or 7:00 but perhaps we can still catch some strong storms. May also try to convince him to take a little detour :whistle:

Yea, pretty impressive. A small area, but very populated nonetheless. Makes me think I should have taken a ride. Buddies of mine live down in silver spring md.

post-5452-0-99786400-1338570178_thumb.jp

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My husband and I are leaving this evening to drive to VA Beach...Looks like our timing will be close since we aren't leaving until 6:30 or 7:00 but perhaps we can still catch some strong storms. May also try to convince him to take a little detour :whistle:

Haha do it! But I'm thinking the the tornado window could be from 5-8. Let us know how you 2 make out.

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Tornado Watch to the west & southwest:

URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 333

NWS STORM PREDICTION CENTER NORMAN OK

150 PM EDT FRI JUN 1 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

DISTRICT OF COLUMBIA

EASTERN MARYLAND

NORTHEAST NORTH CAROLINA

SOUTH-CENTRAL PENNSYLVANIA

NORTHERN AND EASTERN VIRGINIA

COASTAL WATERS

EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 150 PM UNTIL 900

PM EDT.

TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE

MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH NORTHWEST OF

WILMINGTON DELAWARE TO 35 MILES SOUTH SOUTHWEST OF SOUTH HILL

VIRGINIA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 332...

DISCUSSION...THUNDERSTORMS WILL CONTINUE TO INCREASE THROUGH THE

AFTERNOON IN A VERY MOIST AND INCREASINGLY UNSTABLE AIRMASS FROM NC

NWD ACROSS VA...THE DC AREA...MD EASTERN SHORE...AND INTO SRN PA. AT

FIRST...MORE ISOLATED STORMS EXHIBITING WEAK ROTATION WILL POSE A

THREAT FOR ISOLATED SEVERE WEATHER IN THE FORM OF HAIL AND LOCALLY

STRONG WINDS FROM NC INTO SERN VA. WITH TIME...A MORE SUBSTANTIAL

WIND AND ISOLATED TORNADO THREAT WILL EVOLVE AS A STRONG UPPER

TROUGH AND ASSOCIATED COLD FRONT SPREAD EAST. FOCUSED TORNADO THREAT

MAY ALSO EVOLVE ALONG THE WARM FRONT LIFTING ACROSS THE DC/BWI AREA

AND INTO PARTS OF SCNTRL PA LATER THIS AFTERNOON AND EARLY EVENING.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 21030.

...CARBIN

ww0333_radar.gif Hazard Tornadoes EF2+ Tornadoes Likelihood Moderate Moderate Severe Wind 65 kt+ Wind Moderate Moderate Severe Hail

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