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July 2-3 severe weather and flash flooding


Ian

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mcd1253.gif


MESOSCALE DISCUSSION 1253

NWS STORM PREDICTION CENTER NORMAN OK

1105 AM CDT WED JUL 02 2014

AREAS AFFECTED...MUCH OF MD AND VA/PARTS OF ERN WV AND NRN NC

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 021605Z - 021700Z

PROBABILITY OF WATCH ISSUANCE...80 PERCENT

SUMMARY...WW WILL LIKELY BE NEEDED FOR MUCH OF MD AND VA...AND

PORTIONS OF ERN WV AND PERHAPS NRN NC THIS AFTERNOON. TSTMS ARE

EXPECTED TO INCREASE IN COVERAGE...ESPECIALLY ACROSS ERN WV INTO MD

AND NRN/CENTRAL VA. MORE ISOLATED STORM COVERAGE IS EXPECTED

FARTHER SWD INTO NRN NC. STRONG-SEVERE STORMS WILL BE LIKELY

PRODUCING DAMAGING WINDS AND HAIL.

DISCUSSION...MODIFIED 12Z IAD SOUNDING WITH CURRENT SURFACE

TEMPERATURES ALREADY RISING TO AROUND 90 F WITHIN A MOISTURE RICH

ENVIRONMENT RESULTS IN NO INHIBITION FOR SURFACE BASED STORMS...WITH

SBCAPE EXCEEDING 3000 J/KG. THIS INSTABILITY IS CURRENTLY BEING

REALIZED WITH THE TSTMS THAT HAVE FORMED IN ERN WV /TUCKER COUNTY/

INTO THE WRN MD PANHANDLE /GARRETT AND ALLEGANY COUNTIES/.

MEANWHILE...VISIBLE SATELLITE IMAGERY SHOWED CU FORMING ACROSS THE

APPALACHIANS SWD FROM PA TO NERN TN/WRN NC...AND WITHIN A NNE-SSW

CORRIDOR OF LOW-LEVEL CONVERGENCE FROM NRN/WRN VA TO WRN NC. GIVEN

THE UNCAPPED AND VERY STRONG INSTABILITY...TSTMS WILL CONTINUE TO

INCREASE IN COVERAGE/STRENGTH.

STRONGEST MID-UPPER LEVEL FLOW ATTENDANT TO THE GREAT LAKES/OH

VALLEY TROUGH IS EXPECTED ACROSS NRN PORTIONS OF THE DISCUSSION AREA

WITH SUFFICIENT SHEAR FOR STORM ORGANIZATION. MULTICELL STORM MODE

CAN BE EXPECTED...THOUGH SOME TRANSIENT ROTATING STRUCTURES WILL BE

POSSIBLE...ESPECIALLY FROM ERN WV THROUGH NRN VA AND MD...WHERE DEEP

LAYER SHEAR WILL BE STRONGER.

..PETERS/CORFIDI.. 07/02/2014

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Wonder if they'll add a 30% wind.. could see that into northern parts of the area at least. Tho hi res are not emphatic on coverage on the whole.  

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ww0385_overview.gif

 

DISCUSSION...TSTMS FORMING ALONG HIGHER TERRAIN IN ZONE OF
CONFLUENCE ATTENDANT TO UPR IMPULSE NOW OVER WRN PA EXPECTED TO
INCREASE IN COVERAGE/STRENGTH WITH CONTINUED SFC HEATING THROUGH THE
AFTN. WHILE DEEP WSWLY SHEAR DECREASES WITH SWD EXTENT...SUFFICIENT
SHEAR APPEARS PRESENT THROUGHOUT WW AREA PER VWP DATA TO SUPPORT
ORGANIZED STORMS WITH A THREAT FOR LOCALLY DMGG WIND AND PERHAPS SVR
HAIL GIVEN DEGREE OF BUOYANCY/MOISTURE PRESENT.

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Downstream MCD issued for eastern areas as well

 

mcd1254.gif

 

MESOSCALE DISCUSSION 1254
NWS STORM PREDICTION CENTER NORMAN OK
1145 AM CDT WED JUL 02 2014

AREAS AFFECTED...SERN PA/NJ/SERN NY INCLUDING PARTS OF LONG
ISLAND/CT/RI/MA AND SRN NH

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 021645Z - 021745Z

PROBABILITY OF WATCH ISSUANCE...95 PERCENT

SUMMARY...TSTMS ARE EXPECTED TO DEVELOP AND/OR MOVE INTO THE
MID-ATLANTIC TO THE NEW ENGLAND STATES THIS AFTERNOON...WITH STORMS
BECOMING STRONG TO SEVERE PRODUCING DAMAGING WINDS AND HAIL. WW
ISSUANCE IS LIKELY FROM PARTS OF NEW ENGLAND SWD TO NJ...SERN PA AND
PERHAPS PORTIONS OF THE DELMARVA.

DISCUSSION...STRONG SURFACE HEATING HAS RESULTED IN TEMPERATURES
ALREADY AT ABOVE NORMAL READINGS AROUND NOON IN THE UPPER 80S TO
LOWER 90S FROM SERN PA AND NJ NWD TO NH. THIS HEATING OCCURRING
WITHIN THE PRESENCE OF A MOISTURE RICH ENVIRONMENT /PW VALUES OF 1.7
TO NEAR 2 INCHES/ HAS RESULTED IN MODERATE TO STRONG INSTABILITY
ACROSS MUCH OF THE MID-ATLANTIC REGION TO NEW ENGLAND. EFFECTIVE
BULK SHEAR IS EXPECTED TO STRENGTHEN FROM WEST TO EAST AND BECOME
SUFFICIENT FOR MULTICELLS AND PERHAPS A FEW SUPERCELLS. THESE
FACTORS WILL SUPPORT DAMAGING WINDS AND HAIL AS THE PRIMARY THREATS
THROUGH THE AFTERNOON TO EARLY EVENING.

..PETERS/CORFIDI.. 07/02/2014

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Woostorms.

 

...MIDDLE ATLANTIC STATES INTO NEW ENGLAND...

AMPLE MOISTURE WILL PERSIST IN ADVANCE OF THE APPROACHING COLD FRONT

WITH SURFACE DEW POINTS IN THE LOW-MID 70S AND PW VALUES AOA 1.75

INCH. ALTHOUGH MID LEVEL LAPSE RATES WILL BE MODEST AT

BEST...REGIONS OF STRONGER DIABATIC HEATING WILL ENHANCE INSTABILITY

BY LATE MORNING AND AFTERNOON WITH SBCAPE RANGING FROM 1000-1500

J/KG OVER PARTS OF NEW ENGLAND/UPSTATE NY TO CLOSER TO 2000 J/KG

FARTHER SOUTH INTO THE MIDDLE ATLANTIC REGION. CONVECTION IS

EXPECTED TO INCREASE BY EARLY AFTERNOON WITHIN A WEAKLY CAPPED

PRE-STORM ENVIRONMENT AS LARGE SCALE ASCENT INCREASES AHEAD OF THE

UPPER TROUGH AND WITHIN THE RIGHT ENTRANCE REGION OF A STRONG UPPER

LEVEL JET. MODERATELY STRONG SWLY UNIDIRECTIONAL FLOW ALOFT /30-40

KT IN THE 700-500 MB LAYER/ WILL PROVIDE SUFFICIENT VERTICAL SHEAR

FOR ORGANIZED MULTICELL AND ISOLATED BRIEF SUPERCELL STRUCTURES

DURING THE AFTERNOON AND EVENING. DAMAGING WIND GUSTS WILL BE THE

PRIMARY THREAT WITH STRONGER STORMS ALTHOUGH MARGINAL HAIL MAY ALSO

OCCUR.

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Where is my TOR threat? ;)

Tomorrow should be a 2%er given the shear at least. Pretty unidirectional but see if there are boundaries etc. Near the front might do it. 

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BULLETIN - EAS ACTIVATION REQUESTED  

SEVERE THUNDERSTORM WARNING  

NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC  

230 PM EDT WED JUL 2 2014  

 

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A  

 

* SEVERE THUNDERSTORM WARNING FOR...  

SOUTHWESTERN FREDERICK COUNTY IN NORTH CENTRAL MARYLAND...  

SOUTHERN WASHINGTON COUNTY IN NORTH CENTRAL MARYLAND...  

NORTHERN CLARKE COUNTY IN NORTHWEST VIRGINIA...  

JEFFERSON COUNTY IN THE PANHANDLE OF WEST VIRGINIA...  

EASTERN BERKELEY COUNTY IN THE PANHANDLE OF WEST VIRGINIA...  

NORTHERN LOUDOUN COUNTY IN NORTHERN VIRGINIA...  

 

* UNTIL 300 PM EDT  

 

* AT 225 PM EDT...SEVERE THUNDERSTORMS WERE DETECTED ALONG A LINE  

EXTENDING FROM 5 MILES NORTHWEST OF SHEPHERDSTOWN TO 6 MILES  

SOUTHWEST OF CHARLES TOWN...AND WERE MOVING EAST AT 30 MPH. THIS  

LINE OF STORMS IS CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS OF  

60 MPH.  

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