Severe Thunderstorm Warning 229, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
314 PM EDT TUE JUL 24 2012

.SYNOPSIS...
SHOWERS AND THUNDERSTORMS ARE POSSIBLE IN ADVANCE OF A COLD FRONT
THAT WILL MOVE THROUGH THE MID-ATLANTIC REGION THIS EVENING.  HIGH
PRESSURE WILL DOMINATE ON WEDNESDAY...WITH A WARM FRONT MOVING
NORTHWARD THROUGH THE REGION WEDNESDAY NIGHT INTO THURSDAY.  A COLD
FRONT WILL THEN IMPACT THE AREA AT THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
SVR WX IN EFFECT UNTIL 0Z FOR ENTIRE CWA. SVRL AREAS OF FOCUSED
CNVCTN IMPACTING RGN. LONG-LIVED AND SVR MCS DIVING THRU SRN WV AT
18Z LOOKS TO PASS MAINLY S/W OF CWA. SUPERCELL THAT IMPACTED POTOMAC
HIGHLANDS HAS EVOLVED INTO SE-MOVING STORM CLUSTER THAT WILL AFFECT
CNTRL SHEN VLY...FOOTHILLS...AND PORTIONS OF VA PIEDMONT.  N OF
CWA...SCATTERED SHWRS/TSTMS INCRG IN INTENSITY/CVRG ACRS SRN PA IN
ASSOCIATION WITH SFC CDFNT. THIS ACTIVITY WILL SAG SWD INTO CWA
LATER THIS AFTN...LIKELY ORGANIZING FURTHER AS IT DOES.

MOIST/UNSTABLE AIRMASS IN PLACE ACRS CWA. MORE WILL BE KNOWN WHEN
ONGOING 18Z KIAD SOUNDG IS COMPLETED...BUT CAPE VALUES ARE LIKELY
IN 3-4KJ/KG. H8 INVRSN ACRS ERN ZONES HAS SUPPRESSED ACTIVITY...BUT
AS SHRTWV TROF AXIS MOVES E THIS AFTN...TEMPS ALOFT WILL FALL AND
INHIBITION SHUD BE OVERCOME. ASIDE FROM THIS...SUBSTANTIAL AND
PERSISTENT CLOUDCOVER IS MAIN FACTOR IN LACK OF ACTIVITY ACRS
MAJORITY OF CWA THRU ERY AFTN...AND CONTS TO BE SOURCE OF FCST
UNCERTAINTY.  WNW FLOW WILL ADVECT MORE UNSTABLE AIR FROM PA
TDA...AND STRONG M/ULVL WINDS PRODUCING SUFFICIENT SHEAR TO SUPPORT
SVR WIND GUSTS. LARGE HAIL PSBL WITH MORE ROBUST UPDRAFTS...AND
ISOLATED TORNADO CANT BE RULED OUT IN ANY RIGHT-MOVG SUPERCELL.

TEMPS THIS AFTN HAS BEEN HOT OUTSIDE OF RAIN-COOLED
LOCATIONS...L/M90S WITH HEAT INDICES AOA 100F.

CDFNT WILL PROGRESS S OF CWA BY LATE EVE...WITH TSTMS ENDING FROM N
TO S BY AROUND SUNSET. DRIER/COOLER AIR ADVECTS SEWD INTO MID-ATLC
RGN OVNGT...AND MINIMA WILL DROP INTO 60S MAIN AREAS. MOSTLY SUNNY
AND GENERALLY DRY WED...WITH LWR RH AND BRZY NW WINDS. MAXIMA WILL
HOLD AOB NRML...MAINLY M/U80S. REMOTE CHC SHWRS/TSTMS ACRS
SW...WHERE RMNT CDFNT BOUNDARY WILL BE CLOSEST.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
A SHORT WAVE WILL PASS BY TO THE NORTH OF THE REGION WEDNESDAY NIGHT
AND THURSDAY. WARMER AND MORE HUMID AIR SPREADS BACK INTO THE AREA
AS THIS OCCURS. ISOLATED THUNDERSTORMS ARE POSSIBLE ALONG THE
WESTERN HIGHLANDS WEDNESDAY NIGHT...AND ACROSS THE WHOLE REGION
THURSDAY. HIGHER CHANCES OF STORMS WILL BE ALONG THE NORTHERN
BORDER...CLOSER TO A COLD FRONT WHICH WILL SLOWLY MAKE ITS WAY SOUTH
TOWARD THE END OF THE WEEK. THURSDAY WILL BE WARM AND MUGGY WITH
TEMPERATURES IN THE UPPER 90S AND DEWPOINTS APPROACHING THE MID 70S.
THE HEAT INDEX WILL BE OVER 100...HOPEFULLY SOME CLOUD COVER WILL
MITIGATE THE EFFECT OF THE WARM AIR THURSDAY. INSTABILITY SHOWERS
ARE POSSIBLE THURSDAY NIGHT.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
A COLD FRONT SAGS SOUTH ACROSS THE AREA FRIDAY. STRONG
THUNDERSTORMS ARE POSSIBLE. COOLER TEMPERATURES ARE EXPECTED NORTH
OF THE FRONT SATURDAY AS A SHORT WAVE TROF MOVES EAST OF THE AREA.
THERE ARE TIMING UNCERTAINTIES WITH THIS SCENARIO IN OUR FORECAST
MODELS SO WE WILL RETAIN THE THREAT OF THUNDERSTORMS FOR
SATURDAY. MEDIUM RANGE FORECAST MODELS CONTINUE TO SHOW LITTLE
CHANGE IN THE SYNOPTIC WEATHER PATTERN. THE FRONT MAY LIFT BACK
NORTH SUNDAY AND MONDAY AS 500MB HEIGHTS REBUILD OVER THE EASTERN
U.S. AS A RESULT WE HAVE LEFT THE THREAT OF SHOWERS AND
THUNDERSTORMS IN THE FORECAST BOTH DAYS WITH TEMPERATURES
SEASONALLY WARM.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
TSTMS HAVENT ORGANIZED ENUF TO GIVE CONFIDENCE FOR TEMPO TSRA GROUPS
AT TERMINALS BESIDES KCHO...SO VCTS CONTS TO AROUND 0Z.  WHEN MORE
PRECISE ARRIVAL TIMES CAN BE ESTIMATED...TEMPO GROUPS LIKELY WILL BE
INTRODUCED AT RMNG SITES.  SCT/NUM SHWRS/TSTMS WILL LEAD TO
LOCALIZED STRONG WINDS AND SIGNIFICANT FLIGHT RISKS.

CDFNT WILL MOVE SWD TNGT...BRINGING DRIER AIR AND NW WINDS OF AROUND
10 KTS TO MID-ATLC TERMINALS.  SUNNY/VFR WED...WITH NW WINDS PERHAPS
GUSTING TO 20 KTS IN AFTN.

NO SGFNT IMPACTS TO AVIATION XPCD WED-WED NGT. TSTM CHCS WILL INCR
THU AND SPCLY FRI AS CDFNT AND STRONG UPR WAVE APRCH. VFR CONDS
XPCD EXCEPT IN TSTMS.

&&

.MARINE...
SCT/NUM SHWRS/TSTMS XPCD TO IMPACT WATERS THIS AFTN/EVE AS CDFNT
MOVES SWD. STRONG WINDS PSBL IN SOME STORMS AND SMWS MAY BE NEEDED.
SYNOPTICALLY...SWLY WINDS GUSTING TO 20 KTS TDA SUPPORT AN ONGOING
SCA. TNGT...BEHIND CDFNT...NW WINDS WILL CONT TO GUST TO 20 KTS FOR
MOST AREAS...AND ADZY CONTS. GUSTS GRADUALLY SUBSIDE ON WED.

NLY CHANNELING XPCD TO CONT EARLY WED MRNG BUT WILL SUBSIDE BY
MID-DAY AS SFC HIPRES BUILDS INTO THE RGN. STRONGER SWLY WINDS
XPCD ON THU AS WARM SECTOR OVERSPREADS THE RGN. UNUSUALLY STRONG
PRES GRADIENT XPCD THU AFTN AS LEE TROF SHARPENS. GUSTS MAY EXCEED
SMALL CRAFT ADZY THRESHOLD DURG THIS TIME.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ530-531-
     536-539-542.
     SMALL CRAFT ADVISORY UNTIL 9 PM EDT THIS EVENING FOR ANZ535-
     538.
     SMALL CRAFT ADVISORY UNTIL 11 AM EDT WEDNESDAY FOR ANZ532>534-
     537-540-541-543.

&&

SYNOPSIS...SBK
NEAR TERM...SBK
SHORT TERM...SDG
LONG TERM...SDG
AVIATION...SBK/SDG
MARINE...SBK/SDG

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
110 PM EDT TUE JUL 24 2012

ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057-
251030-
CHESAPEAKE BAY NORTH OF POOLES ISLAND MD-
CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT MD-
CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH MD-
CHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT MD-
CHESAPEAKE BAY FROM DRUM POINT MD TO SMITH POINT VA-
TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD MD-
TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND MD-
TIDAL POTOMAC FROM COBB ISLAND MD TO SMITH POINT VA-
PATAPSCO RIVER INCLUDING BALTIMORE HARBOR-
CHESTER RIVER TO QUEENSTOWN MD-EASTERN BAY-
CHOPTANK RIVER TO CAMBRIDGE MD AND THE LITTLE CHOPTANK RIVER-
PATUXENT RIVER TO BROOMES ISLAND MD-
TANGIER SOUND AND THE INLAND WATERS SURROUNDING BLOODSWORTH
ISLAND-DISTRICT OF COLUMBIA-NORTHERN BALTIMORE-HARFORD-
SOUTHERN BALTIMORE-PRINCE GEORGES-ANNE ARUNDEL-CHARLES-ST. MARYS-
CALVERT-PRINCE WILLIAM/MANASSAS/MANASSAS PARK-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-STAFFORD-SPOTSYLVANIA-
KING GEORGE-
110 PM EDT TUE JUL 24 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE MARYLAND PORTION OF THE
CHESAPEAKE BAY...TIDAL POTOMAC RIVER...AND ADJACENT COUNTIES IN
CENTRAL MARYLAND AND NORTHERN VIRGINIA AS WELL AS THE DISTRICT OF
COLUMBIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL 800 PM EDT. SHOWERS
AND THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS AFTERNOON ALONG
AND SOUTH OF A SLOW-MOVING COLD FRONT. SOME STORMS WILL BECOME
SEVERE AND WILL BE CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND
POSSIBLY LARGE HAIL.

A SMALL CRAFT ADVISORY IS IN EFFECT THROUGH TONIGHT FOR PORTIONS
OF THE WATERS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

A SMALL CRAFT ADVISORY IS IN EFFECT THROUGH 11 AM WEDNESDAY FOR A
PORTION OF THE WATERS.

A HEAT ADVISORY MAY BE NEEDED ON THURSDAY FOR A LARGE PORTION OF
THE OUTLOOK AREA AS HEAT INDICES MAY EXCEED 105 DEGREES.

SEVERE THUNDERSTORMS ARE POSSIBLE ON THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS HAVE BEEN ACTIVATED. PLEASE RELAY REPORTS OF SEVERE
WEATHER TO LAW ENFORCEMENT OR THE NATIONAL WEATHER SERVICE.

MDZ003>005-009-010-501-502-VAZ025>031-036>040-042-050-051-501>504-
WVZ050>053-055-501>506-251030-
WASHINGTON-FREDERICK MD-CARROLL-MONTGOMERY-HOWARD-
EXTREME WESTERN ALLEGANY-CENTRAL AND EASTERN ALLEGANY-AUGUSTA-
ROCKINGHAM-SHENANDOAH-FREDERICK VA-PAGE-WARREN-CLARKE-NELSON-
ALBEMARLE-GREENE-MADISON-RAPPAHANNOCK-LOUDOUN-ORANGE-CULPEPER-
NORTHERN FAUQUIER-SOUTHERN FAUQUIER-WESTERN HIGHLAND-
EASTERN HIGHLAND-HAMPSHIRE-MORGAN-BERKELEY-JEFFERSON-HARDY-
WESTERN GRANT-EASTERN GRANT-WESTERN MINERAL-EASTERN MINERAL-
WESTERN PENDLETON-EASTERN PENDLETON-
110 PM EDT TUE JUL 24 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN WEST VIRGINIA...
NORTHERN AND CENTRAL VIRGINIA...AND CENTRAL AND WESTERN MARYLAND
WITH THE EXCEPTION OF GARRETT COUNTY.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL 800 PM EDT.
THUNDERSTORMS WILL CONTINUE DEVELOP THIS AFTERNOON ALONG AND
AHEAD OF A COLD FRONT. SOME STORMS WILL SEVERE AND WILL BE CAPABLE
OF DAMAGING WIND GUSTS AND POSSIBLY LARGE HAIL. IF AN ORGANIZED
STORM SYSTEM DEVELOPS...VERY DAMAGING WIND GUSTS WILL BE
POSSIBLE...ESPECIALLY FROM THE POTOMAC HIGHLANDS TO THE SHENANDOAH
VALLEY AND CENTRAL FOOTHILLS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

A HEAT ADVISORY MAY BE NEEDED ON THURSDAY FOR COUNTIES EAST OF THE
BLUE RIDGE MOUNTAINS AS HEAT INDICES MAY EXCEED 105 DEGREES.

SEVERE THUNDERSTORMS ARE POSSIBLE ON THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS HAVE BEEN ACTIVATED. PLEASE RELAY REPORTS OF SEVERE
WEATHER TO LAW ENFORCEMENT OR THE NATIONAL WEATHER SERVICE.

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
422 PM EDT TUE JUL 24 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0116 PM     TSTM WND DMG     LOST RIVER              38.95N  78.80W
07/24/2012                   HARDY              WV   DEPT OF HIGHWAYS

            MULTIPLE TREES DOWN ALONG MILL GAP-THORNE BOTTOM RD ONE
            HALF MILE EAST OF RT 239.

&&

EVENT NUMBER LWX1200977

SMZ

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