Severe Thunderstorm Warning 20, NWS Baltimore/Washington

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
520 PM EDT WED MAR 23 2011

.SYNOPSIS...
LOW PRESSURE WILL PASS THROUGH THE REGION TONIGHT. CANADIAN HIGH
PRESSURE WILL BUILD IN BEHIND THIS SYSTEM FOR THURSDAY AND FRIDAY. A
SERIES OF DISTURBANCES WILL PASS THROUGH THE REGION DURING THE
WEEKEND INCREASING CHANCES FOR PRECIPITATION.

&&

.NEAR TERM /THROUGH THURSDAY/...
UPDATE...ISSUED SCA FOR THE LOWER TWO TIDAL POTOMAC ZONES W/ ESELY
WINDS CHANNELING INTO THESE ZONES AHEAD OF AN INCOMING LOW
PRESSURE SYSTEM.

PREV UPDATE...SEVERE THUNDERSTORM WATCH 57 IN EFFECT FOR THE WRN
2/3RDS OF THE CWA THRU 11 PM. AREAS EAST OF I-95 NOT IN THIS WATCH
MAY BE PLACED INTO A SUBSEQUENT WATCH LATER THIS EVE IF TRENDS
SHOW STORMS ARE MAINTAINING THEIR STRENGTH/SEVERITY AS THEY MOVE
EAST. CURRENTLY THOUGH...THE INITIAL WAVE OF CONVECTION /WELL
AHEAD OF THE ACTUAL COLD FRONT/ NOW CLEARING THE CNTRL APLCNS
WITHIN THE NEXT HR/TWO AND WILL SEE HOW THESE CELLS FARE AS THEY
APPROACH THE SHENANDOAH VLY AND THE MORE STABLE AIR THAT LIES EAST
OF THE BLUE RIDGE.

FROM PREV DISC...
WARM FRONT STILL ACROSS THE CWFA THIS AFTERNOON...ALONG A LINE
FROM SOUTHERN GRANT COUNTY THROUGH THE SHENANDOAH VALLEY TO JUST
EAST OF CHARLOTTESVILLE. SOUTH OF THE FRONT...TEMPS HAVE RISEN
INTO THE 60S AND LOWER 70S. NORTH OF THE WARM FRONT...IN THE
EASTERLY FLOW...TEMPS ARE MAINLY IN THE 40S AN 50S. FRONT MAY LIFT
A LITTLE FURTHER NORTHWARD THIS AFTERNOON...ESPECIALLY ACROSS THE
HIGHLANDS. THE NORTHEAST CWFA WILL PROBABLY REMAIN FIRMLY
ENTRENCHED IN THE COOLER WEDGE. SEVERE THUNDERSTORMS ARE MOST
LIKELY JUST ALONG AND SOUTH OF THE WARM FRONT LATE THIS AFTERNOON
AND EVENING. AS THUNDERSTORMS CROSS NORTH OF THE WARM FRONT AND
BECOME ELEVATED INSTEAD OF SURFACE BASED...HAIL WILL STILL BE
POSSIBLE. HAVE TRIED TO INDICATE THIS WITH A TRANSITION ZONE
BETWEEN THE WARM FRONT AND THE MOST STABLE AREA OF THE CWFA.

SURFACE LOW WILL MOVE SOUTHEAST ACROSS THE CWFA THIS EVENING...AND
EMERGE OFFSHORE NEAR THE MOUTH OF THE CHESAPEAKE BAY BY THE EARLY
MORNING. MOST OF THE PRECIP SHOULD END BY MIDNIGHT...WITH SOME
LINGERING ACTIVITY ACROSS THE POTOMAC HIGHLANDS. A RA/SN MIX IS
POSSIBLE ACROSS THE WESTERN SLOPES.

500MB TROUGH MOVES THROUGH THE CWFA DURING THE DAY TOMORROW. CHANCE
OF SHOWERS WILL BE POSSIBLE.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/...
CANADIAN HIGH PRESSURE WILL BUILD OVER THE REGION THURSDAY NIGHT
THROUGH FRIDAY...BRINGING DRY AND CHILLY CONDITIONS. MIN TEMPS
THURSDAY NIGHT WILL RANGE FROM THE TEENS IN THE POTOMAC HIGHLANDS TO
THE LOWER 30S IN DOWNTOWN WASHINGTON AND BALTIMORE.

MAX TEMPS FRIDAY WILL RANGE FROM THE 30S IN THE ALLEGHENY HIGHLANDS
TO THE MID 50S IN CENTRAL VIRGINIA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
CANADIAN HIGH PRESSURE WILL REMAIN JUST TO OUR NORTH THROUGHOUT THE
PERIOD KEEPING COLD AIR IN PLACE WHILE STORM SYSTEMS PASS BY TO OUR
SOUTH IN A ZONAL FLOW ALOFT. THE EXACT TRACK AND TIMING OF THESE
SYSTEMS REMAINS UNCERTAIN AT THIS TIME...BUT THERE IS A GOOD CHANCE
FOR UNSETTLED WEATHER FOR THE WEEKEND THROUGH THE MIDDLE OF NEXT
WEEK.

WITH THE TRACK OF STORMS LIKELY STAYING TO THE SOUTH AND THE SOURCE
REGION OF THE COLD AIR BEING FROM CANADA...THERE IS A CHANCE FOR
WINTRY PRECIPITATION ACROSS PORTIONS OF THE AREA DURING THIS TIME.
THE BEST CHANCE FOR ANY WINTRY PRECIPITATION WILL BE ACROSS THE
NORTHERN AND WESTERN CWA.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
NORTHEAST CWFA STILL IN COOL WEDGE...WITH IFR CIGS ACROSS THE MAJOR
HUBS. FURTHER WEST...VFR/MVFR CIGS/VSBYS PREVAIL. LOW PRESSURE/COLD
FRONT WILL MOVE EAST ACROSS THE CWFA OVERNIGHT...BRINGING WIDESPREAD
SHOWERS AND THUNDERSTORMS. MOST ACTIVE PERIOD LOOKS TO BE LATE THIS
AFTERNOON INTO THE EVENING. EVEN AFTER THE FROPA...MODEL SOUNDINGS
KEEP CIGS IN THE IFR RANGE OVERNIGHT. SLOW IMPROVEMENT TO MVFR IS
EXPECTED LATE THURSDAY MORNING/EARLY THURSDAY AFTERNOON.

WIND SHIFT TO THE NW EXPECTED AFTER THE FROPA. WINDS EXPECTED TO
GUST BETWEEN 20 AND 25 KT TOMORROW.

HIGH PRESSURE WILL BRING VFR CONDITIONS THURSDAY NIGHT THROUGH
FRIDAY. WAVES OF LOW PRESSURE WILL PASS BY TO THE SOUTH FOR THE
WEEKEND INTO EARLY NEXT WEEK...BRINGING UNSETTLED CONDITIONS.

&&

.MARINE...
SE FLOW CONTINUES ACROSS THE WATERS THIS AFTERNOON WITH SUSTAINED
SPEEDS AROUND 15 KT. LOW PRESSURE/COLD FRONT WILL IMPACT THE WATERS
THIS EVENING. THUNDERSTORMS WILL HAVE THE POTENTIAL TO PRODUCE GUSTY
WINDS AND HAIL. SPECIAL MARINE WARNINGS ARE POSSIBLE.

WINDS WILL SHIFT TO THE NW BEHIND THE FROPA THIS EVENING. NW WINDS
WILL GUSTS BETWEEN 20 AND 25 KT TOMORROW.

WILL CONTINUE WITH A SMALL CRAFT ADVISORY THURSDAY NIGHT FOR THE
CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER AS NORTHERLY WINDS
CHANNEL DOWN THESE LOCATIONS BEHIND A COLD FRONT. A SMALL CRAFT
ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS FRIDAY BEFORE HIGH
PRESSURE BUILDS OVERHEAD.

WAVES OF LOW PRESSURE WILL PASS BY TO THE SOUTH OF THE WATERS DURING
THE WEEKEND INTO EARLY NEXT WEEK...BRINGING UNSETTLED CONDITIONS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM THURSDAY TO 6 AM EDT FRIDAY FOR
     ANZ530>534-537>543.
     SMALL CRAFT ADVISORY FROM 2 AM TO 6 PM EDT THURSDAY FOR ANZ535-
     536.
     SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ536-
     537.

&&

UPDATE...GMS
PREV DISCUSSION...LISTEMAA/LASORSA

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
604 PM EDT WED MAR 23 2011

ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057-
241115-
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-
604 PM EDT WED MAR 23 2011

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...TONIGHT

SEVERE THUNDERSTORM WATCH NUMBER 57 REMAINS IN EFFECT FOR THE
I-95 CORRIDOR OF NORTHERN VIRGINIA AND EASTERN MARYLAND...WITH THE
EXCEPTION OF PRINCE GEORGES COUNTY...BALTIMORE AND HARFORD
COUNTIES. THE WATCH IS IN EFFECT THROUGH 11 PM TONIGHT.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON
AND EVENING AS LOW PRESSURE AND A COLD FRONT MOVES EAST ACROSS
THE MID ATLANTIC. SOME OF THE THUNDERSTORMS MAY BECOME
SEVERE...ESPECIALLY ACROSS THE SOUTHERN SUBURBS OF WASHINGTON
DC AND PORTIONS OF THE NORTHERN VIRGINIA PIEDMONT. ANY SEVERE
STORMS THAT DEVELOP WILL HAVE THE POTENTIAL TO PRODUCE DAMAGING
WIND GUSTS AND LARGE HAIL.

SPECIAL MARINE WARNINGS LIKELY WILL BE NEEDED THIS AFTERNOON AND
EVENING AS THUNDERSTORMS APPROACH THE MARYLAND CHESAPEAKE BAY AND
TIDAL POTOMAC RIVER.

A SMALL CRAFT ADVISORY IS IN EFFECT THROUGH LATE TONIGHT FOR THE
LOWER TIDAL POTOMAC RIVER.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

A SMALL CRAFT ADVISORY IS IN EFFECT THURSDAY FOR THE MARYLAND
CHESAPEAKE BAY AND TIDAL POTOMAC RIVER. A SMALL CRAFT ADVISORY IS
IN EFFECT THURSDAY NIGHT FOR THE MARYLAND CHESAPEAKE BAY AND FOR
THE TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT.

A SMALL CRAFT ADVISORY MAY BE WARRANTED FOR PORTIONS OF THE WATERS
FRIDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION LIKELY WILL BE NEEDED LATE THIS AFTERNOON AND
EVENING.

MDZ003>005-009-010-501-502-VAZ025>031-036>040-042-050-051-501>504-
WVZ050>053-055-501>506-241115-
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-
604 PM EDT WED MAR 23 2011

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...TONIGHT

SEVERE THUNDERSTORM WATCH NUMBER 57 REMAINS IN EFFECT FOR MUCH OF
NORTHERN VIRGINIA AND MARYLAND...EAST OF THE I-95 CORRIDOR AND
INCLUDING THE EASTERN WEST VIRGINIA PANHANDLE THROUGH 11 PM
TONIGHT.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS AFTERNOON
AND EVENING AS LOW PRESSURE AND A COLD FRONT MOVES EAST ACROSS
THE MID ATLANTIC. SOME OF THE THUNDERSTORMS MAY BECOME
SEVERE...WITH THE PRIMARY THREATS BEING DAMAGING WIND GUSTS AND
LARGE HAIL.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION LIKELY WILL BE NEEDED LATE THIS AFTERNOON AND
EVENING.

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