Severe Thunderstorm Warning 228, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
927 PM EDT THU JUN 16 2011

.SYNOPSIS...
LOW PRESSURE OVER THE MIDWEST WILL MOVE EAST ACROSS THE NORTHERN MID
ATLANTIC THROUGH FRIDAY. A FRONTAL BOUNDARY TRAILING THE LOW WILL
STALL FROM THE OHIO VALLEY TO THE SOUTHERN MID ATLANTIC THROUGH
THE WEEKEND BEFORE RETURNING AS A WARM FRONT IN THE TUESDAY
TIMEFRAME. A COLD FRONT WILL APPROACH FROM THE WEST IN THE LATTER
PART OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
RECENT INCREASE IN COVERAGE...AND TO SOME DEGREE INTENSITY...HAS
OCCURRED WITH CONVECTION THIS EVENING. THIS IS LIKELY COINCIDING
WITH INCREASED PVA/LIFT AHEAD OF AN APPROACHING SHORTWAVE AND A
SLIGHT INCREASE IN SHEAR. 00Z KIAD SOUNDING INDICATED SOME CAPE
TOO...HOWEVER WOULD THINK THAT INSTABILITY WOULD BE ON THE WANE AS
THE NIGHT PROGRESSES. THEREFORE...BELIEVE SEVERE THREAT IS
ISOLATED AND LIMITED TO WITHIN THE NEXT COUPLE OF HOURS BUT CANT
RULE OUT A PULSE SEVERE STORM FOR LARGE HAIL FOR THE REST OF THE
EVENING.

POPS/WX HAVE BEEN RE-ADJUSTED TO LATEST RADAR TRENDS...WHICH
FAVORED HIGH END SCATTERED TO NUMEROUS SHRA/ISOLATED TSRA THROUGH
AT LEAST MIDNIGHT. SHORTWAVE MOVES THROUGH FROM THE WEST
OVERNIGHT...A DECREASE IN CONVECTION SHOULD FOLLOW SUIT. MID CLOUDS
MAY HOLD ON FOR A WHILE AFTER THAT...AND THAT SHOULD HELP TO LIMIT
FOG POTENTIAL.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
FRIDAY...UPR LOW PUSHES EAST ACROSS PA...BRINGING A WIND SHIFT FROM
SLY TO W-SWLY THROUGH THE DAY. WITH PVA AHEAD OF THE UPR LOW...ADDED
LIKELY POPS FOR THUNDERSTORMS IN THE GREATER BALTIMORE AREA FOR
MIDDAY WITH CHANCE POPS ACROSS THE CWA IN THE AFTERNOON IN
DOWNSLOPING FLOW. EXPECT AFTERNOON ACTIVITY TO BE MAINLY ALONG THE
FRONTAL BOUNDARY SAGGING SOUTH ACROSS THE AREA. CONTINUED LOW QPF
DUE TO THE SLY LLVL CONNECTION CUTTING OFF BEHIND THE COLD FRONT
WHICH PROVIDES DOWNSLOPING FLOW. MAX TEMPS MID TO UPR 80S BALT-WASH
AND WEST...NEAR 90F SOUTH.

FRIDAY NIGHT...COLD FRONT DIPS TO SRN PERIPHERY OF THE CWA...THOUGH
A LITTLE SLOWER THAN ANTICIPATED YESTERDAY. ALLOWED FOR SOME EVENING
POP CHANCES SOUTHWEST OF BALTIMORE...THEN THE ONLY POPS FOR THE
OVERNIGHT ARE LOW CHANCES FROM KCHO AND WEST. MIN TEMPS REMAIN UP
WITH LINGERING SFC MOISTURE AND MIXING...NEAR 60F WEST...LOW 60S
INLAND EAST OF THE BLUE RIDGE...MID 60S FOR URBAN/NEAR SHORE.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
THIS WEEKEND...LOW PRESSURE SWINGS SOUTH FROM QUEBEC TO NORTHERN NEW
ENGLAND...SLOWING THE EASTWARD PROGRESS OF THE RIDGE TO THE WEST.
WITH THE PATTERN STALLED...ACTIVE WEATHER LOOKS TO MAINLY STAY SOUTH
OF BALT-WASH ON SATURDAY...ALONG THE FRONT FROM THE ERN OH VLY TO
THE NC/VA BORDER. ON SUNDAY THOUGH...THE 12Z GFS AND 00Z ECMWF ALLOW
A NLY PUSH TO THE BOUNDARY...BRINGING CHANCES FOR THUNDERSTORMS BACK
NORTH INTO THE CENTRAL MID ATLANTIC FOR SATURDAY NIGHT AND SUNDAY.
TEMPERATURES THROUGH THE WEEKEND LOOK TO REMAIN ABOVE NORMAL...MAX
TEMPS UPR 80S TO LOW 90S.

THE NERN CONUS TROUGH LIFTS NORTH EARLY NEXT WEEK BRINGING A WARM
FRONT THROUGH THE REGION IN THE TUESDAY TIMEFRAME...CHANCES FOR
THUNDERSTORMS CONTINUE INTO TUESDAY NIGHT. THE 12Z GFS IS WARMER
THAN THE 00Z ECMWF...WITH THE FORMER BRINGING 20C OR GREATER 850
TEMPS FOR TUESDAY AND PARTICULARLY WEDNESDAY...WHILE THE LATTER
KEEPS 850 TEMPS BELOW 20C THROUGH THE FIRST HALF OF NEXT WEEK. AS OF
NOW...EXPECT A WARMUP IN THE MIDWEEK TIMEFRAME...DETAILS/POTENTIAL
FOR HAZARDOUS HEAT REMAIN TBD.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
SCATTERED CONVECTION WILL LINGER ACROSS THE HUBS INTO THE EARLY
NIGHT HOURS. HARD TO PINPOINT INDIVIDUAL DIRECT HITS...ESPECIALLY
FURTHER OUT IN TIME. VICINITY/CBS CURRENTLY PREVAIL IN TAFS.
DIRECT HITS MAY RESULT IN BRIEF IFR/MVFR VSBYS WHICH WOULD BE
COVERED IN TEMPO. CONVECTION SHOULD COME TO AN END LATER AT NIGHT
WITH PASSAGE OF A SHORTWAVE. MVFR FOG COULD FORM LATE AT
NIGHT...BUT WITH INITIAL CONVECTION AND THEN LINGERING MID CLOUDS
FOG FORMATION MAY BE INTERRUPTED.

BEST CHANCES FOR SHOWERS AND THUNDERSTORMS CONTINUE THROUGH FRIDAY
MORNING AHEAD OF A FRONTAL BOUNDARY. SCATTERED LIGHT SHOWERS AND
ISOLATED THUNDERSTORMS THEN FRIDAY AFTERNOON WITH SWLY FLOW AROUND
10 KT. THE FRONTAL BOUNDARY STALLS OVER THE SRN MID ATLANTIC
SATURDAY...WITH MORE SWLY FLOW AROUND 10 KT. A WARM FRONT ENTERS THE
AREA SUNDAY...WITH WLY FLOW 15 TO 20 KT IN THE AFTERNOON. CHANCES
FOR THUNDERSTORMS ON SUNDAY AND AT TIMES THROUGH THE FIRST HALF OF
NEXT WEEK.

&&

.MARINE...
SOUTHERLY WINDS HAVE BEEN PROMOTING SCA CONDITIONS UP THE
BAY/LOWER POTOMAC ON THEIR OWN...AND CONVECTION HAS RESULTED IN
LOCALLY HIGHER GUSTS. SCA WILL CONTINUE OVER A PORTION OF THE BAY
INTO THE OVERNIGHT HOURS.

10 TO 15KT SLY FLOW BECOMES SWLY FRIDAY MORNING...THEN WLY/NWLY
THROUGH THE WEEKEND AS A FRONTAL BOUNDARY REMAINS ACROSS THE
SOUTHERN MID ATLANTIC. GUSTS TO AROUND 20 KT ARE EXPECTED SUNDAY
AFTERNOON...SO A SMALL CRAFT IS LIKELY TO BE NEEDED THEN. SCATTERED
THUNDERSTORMS ALSO SUNDAY AFTERNOON.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES HAVE INCREASED THIS EVENING...UP TO 1.5 FT ABOVE
NORMAL. THESE ANOMALIES WILL LIKELY REMAIN STEADY STATE THROUGH
THE OVERNIGHT HOURS...AND LAST INTO THE HIGH TIDE CYCLE WEDNESDAY
MORNING DESPITE A WIND SHIFT TO THE WEST OCCURRING IN THE MORNING.
COASTAL FLOOD ADVISORY IS ALREADY IN EFFECT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL NOON EDT FRIDAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY FROM 3 AM TO NOON EDT FRIDAY FOR MDZ007-
     011-014-018.
VA...COASTAL FLOOD ADVISORY UNTIL NOON EDT FRIDAY FOR VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ531>533-
     536>542.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ534-543.

&&

SYNOPSIS...BPP/BAJ
NEAR TERM...BPP/HTS
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BPP/BAJ/HTS
MARINE...BPP/BAJ/HTS
TIDES/COASTAL FLOODING...BPP

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
637 PM EDT THU JUN 16 2011

ANZ530>543-DCZ001-MDZ006-007-011-013-014-016>018-VAZ052>057-
171000-
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-
637 PM EDT THU JUN 16 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

SCATTERED SHOWERS AND THUNDERSTORMS WILL AFFECT THE AREA THROUGH
THIS EVENING. AN ISOLATED STRONG TO SEVERE THUNDERSTORM WITH LARGE
HAIL AND DAMAGING WINDS WILL BE POSSIBLE.

A COASTAL FLOOD ADVISORY HAS BEEN ISSUED FOR SENSITIVE AREAS ALONG
THE UPPER TIDAL POTOMAC RIVER...INCLUDING ALEXANDRIA...FOR THIS
EVENINGS HIGH TIDE.

A SMALL CRAFT ADVISORY IS IN EFFECT FOR PORTIONS OF THE TIDAL
POTOMAC RIVER AND MARYLAND CHESAPEAKE BAY TONIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A COASTAL FLOOD ADVISORY IS IN EFFECT THROUGH NOON WEDNESDAY FOR
AREAS ADJACENT TO THE UPPER TIDAL POTOMAC RIVER AND ALONG THE
WESTERN SHORE OF THE CHESAPEAKE BAY. PLEASE REFER TO THE COASTAL
HAZARD MESSAGE PRODUCT /WBCCFWLWX/ FOR FURTHER DETAILS.

.SPOTTER INFORMATION STATEMENT...

GIVEN THE EXPECTED ISOLATED NATURE OF ANY SEVERE WEATHER THREAT
THIS EVENING...SPOTTER ACTIVATION WILL LIKELY NOT BE REQUIRED
THIS EVENING.

MDZ003>005-009-010-501-502-VAZ025>031-036>040-042-050-051-501>504-
WVZ050>053-055-501>506-171000-
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-
637 PM EDT THU JUN 16 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

SCATTERED SHOWERS AND THUNDERSTORMS WILL AFFECT THE AREA THROUGH
THIS EVENING. AN ISOLATED STRONG TO SEVERE THUNDERSTORM WITH LARGE
HAIL AND DAMAGING WINDS WILL BE POSSIBLE...MAINLY ACROSS NORTHWEST
MARYLAND AND THE EASTERN WEST VIRGINIA PANHANDLE.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

GIVEN THE EXPECTED ISOLATED NATURE OF ANY SEVERE WEATHER THREAT
THIS EVENING...SPOTTER ACTIVATION WILL LIKELY NOT BE REQUIRED
THIS EVENING.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
945 PM EDT THU JUN 16 2011

MDZ003-WVZ051-052-170215-
WASHINGTON MD-BERKELEY WV-MORGAN WV-
945 PM EDT THU JUN 16 2011

...STRONG THUNDERSTORM TO AFFECT WASHINGTON...BERKELEY AND MORGAN
COUNTIES...

AT 945 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER
BERKELEY SPGS...MOVING EAST AT 20 MPH.

LOCATIONS IMPACTED INCLUDE NEW HOPE...SPOHRS CROSSROADS...SPRUCE PINE
HOLLOW AND SLEEPY CREEK.

THIS STORM IS PRODUCING FREQUENT CLOUD TO GROUND LIGHTNING. MOVE
INDOORS IMMEDIATELY FOR YOUR SAFETY. IF YOU CAN HEAR THUNDER...YOU
ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.

HEAVY RAIN WITH THIS STORM MAY REDUCE VISIBILITIES TO BELOW ONE MILE
AND MAY CAUSE PONDING OF WATER ON ROADWAYS.

WIND GUSTS OF 40 TO 50 MPH AND SMALL HAIL CAN BE EXPECTED WITH THIS
STORM.

&&

LAT...LON 3943 7793 3952 7836 3973 7829 3973 7789
TIME...MOT...LOC 0145Z 270DEG 18KT 3965 7823

SBK

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
954 PM EDT THU JUN 16 2011

VAZ030-040-501-502-170245-
RAPPAHANNOCK VA-NORTHERN FAUQUIER VA-WARREN VA-SOUTHERN FAUQUIER VA-
954 PM EDT THU JUN 16 2011

...STRONG THUNDERSTORM TO AFFECT RAPPAHANNOCK...NORTHERN FAUQUIER...
WARREN AND SOUTHERN FAUQUIER COUNTIES...

AT 954 PM EDT...DOPPLER RADAR INDICATED A STRONG THUNDERSTORM OVER
CHESTER GAP...MOVING EAST AT 20 MPH.

LOCATIONS IMPACTED INCLUDE HUME...DELAPLANE...THE PLAINS AND
WARRENTON.

STORM INTENSITY IS INCREASING...AND SEVERE WEATHER MAY DEVELOP
RAPIDLY. REMAIN ALERT...AND BE PREPARED TO TAKE ACTION IF WARNINGS
ARE ISSUED.

THIS STORM IS PRODUCING FREQUENT CLOUD TO GROUND LIGHTNING. MOVE
INDOORS IMMEDIATELY FOR YOUR SAFETY. IF YOU CAN HEAR THUNDER...YOU
ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING.

HEAVY RAIN WITH THIS STORM MAY REDUCE VISIBILITIES TO BELOW ONE MILE
AND MAY CAUSE PONDING OF WATER ON ROADWAYS.

PENNY-SIZE TO NICKEL-SIZE HAIL AND WIND GUSTS OF 40 TO 50 MPH CAN BE
EXPECTED WITH THIS STORM.

&&

LAT...LON 3896 7777 3869 7775 3875 7826 3893 7825
TIME...MOT...LOC 0154Z 273DEG 18KT 3884 7813

SBK