Severe Thunderstorm Warning 9, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
330 PM EDT FRI APR 19 2013

.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE REGION FROM WEST TO EAST THIS
AFTERNOON AND EVENING. WIDESPREAD SHOWERS AND THUNDERSTORMS ARE
EXPECTED ALONG AND AHEAD OF THE BOUNDARY. CANADIAN HIGH PRESSURE
WILL BUILD INTO THE REGION LATE TONIGHT THROUGH SUNDAY...BRINGING
DRY AND COOL CONDITIONS. HIGH PRESSURE WILL REMAIN OVERHEAD EARLY
NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
HEADLINE UPDATE...TORNADO WATCH NUMBER 131 IS NOW IN EFFECT FOR
MUCH OF THE MID-ATLANTIC REGION THROUGH 10 PM TONIGHT.

FROM PREV DISC... 18Z SURFACE OBSERVATIONS INDICATES COLD FRONT
IS MOVING ACROSS WV AND WRN PA. DEW POINTS BEHIND THE COLD FRONT
OVER WRN WV HAVE DROPPED INTO THE 40S...WHILE DEW POINTS OVER OUR
CWA HAVE MADE IT INTO THE 60S OVER MOST LOCATIONS. THE FRONT IS
STILL EXPECTED TO SWEEP ACROSS THE FORECAST AREA FROM MID
AFTERNOON THROUGH THIS EVENING.

THIN LINE OF CONVECTION IS TRYING TO DEVELOP AHEAD OF THE FRONT
OVER EASTERN WV. TSTMS ARE EXPECTED TO INCREASE IN COVERAGE THIS
AFTERNOON UNDER FAVORABLE DYNAMICS. INSTABILITY HAS BEEN THE
LIMITING FACTOR DUE TO ONGOING CLOUD COVER...BUT SOME BREAKS HAVE
DEVELOPED. MOISTURE WILL CONTINUE TO INCREASE DUE TO SOUTHERLY
FLOW. A VERY STRONG JET WILL STREAK WILL CROSS THE AREA WITH 50+KT
WINDS ABOVE 850MB AHEAD OF THE FRONT. SPC HAS ISSUED A MESOSCALE
DISCUSSION ABOUT THE UPDATED SEVERE THREAT...INCLUDING POTENTIAL
FOR A TORNADO WATCH THIS AFTERNOON.

THE COLD FRONT WILL MOVE OFF TO OUR EAST OVERNIGHT AND ANY
LEFTOVER SHOWERS WILL ALSO MOVE OUT OF OUR AREA. MIN TEMPS
OVERNIGHT WILL BE NOTICEABLY CHILLIER COMPARED TO RECENT
NIGHT...RANGING FROM THE 20S ALONG THE RIDGE TOPS IN THE POTOMAC
HIGHLANDS...TO THE MID AND UPPER 40S NEAR WASHINGTON/BALTIMORE...
TO THE LOWER 50S ACROSS SOUTHERN MARYLAND.

&&

.SHORT TERM /SATURDAY/...
HIPRES BLDS OVER THE RGN THIS WKND. WL BE IN CAA REGIME MOST OF THE
TIME...W/ NW/NLY FLOW SAT BCMG NE/ELY SUN AS CENTER OF HIGH HEADS
TWD NEW ENGLND/QUE. SHUD BE DIURNAL CU SAT...SPCLY IN THE MTNS. BY
SUN...SUBSIDENCE SHUD PREVAIL.

TEMPS WL BE BLO CLIMO SAT...AND DROP A CPL MORE BY SUN. LTST
MOS/GOING FCST IN GOOD AGREEMENT. GROWING SEASON HAS STARTED E OF
BLURDG. ALTHO IT WL BE CHILLY SAT NGT...A LGT NLY BRZ AS CURRENTLY
PROGGED WUD PRECLUDE EITHER FROST OR SUBFRZG TEMPS. RECENT TEMP BIAS
HAS BEEN TO FCST TOO COLD. WL OMIT FROM HWO ATTM AS POTL FOR
HEADLINE CONDS SLIM.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
THE STREAK OF GOOD WX WEEKENDS CONTINUES THIS WEEKEND...THOUGH DON'T
FORGET A JACKET FOR OUTDOOR PLANS. EACH DAY WILL BE COOL AND WELL
BELOW AVERAGE FOR THIS TIME OF YEAR. BREEZY ON SATURDAY...THE DAY
AFTER THE FRONTAL PASSAGE AND STILL COOL ON SUNDAY FROM THE NELY
ONSHORE FLOW. HIGHS EACH DAY WILL BARELY PEAK NEAR 60 DEG AND THE
COOLER WINDS WILL BRING THAT VALUE DOWN EVEN A FEW MORE DEG IN TERMS
OF APPARENT TEMPS. SKIES WILL CLEAR OUT ON SAT...AFTER NEARLY A WEEK
OF MOSTLY CLOUDY/CLOUDY SKIES - STAYING CLEAR INTO SUN MRNG.

A WEAK UPPER WAVE WILL QUICKLY SLIDE ACROSS THE GREAT LAKES REGION
ON SUN...PUSHING SOME UPPER LEVEL CLOUD COVER OVER THE AREA BUT THE
NEXT WX FEATURE AFFECTING THE AREA WILL COME FROM THE SOUTH. THE
FRONTAL BOUNDARY THAT WILL BE MOVING ACROSS THE AREA TONIGHT WILL
STALL WELL OFF THE COAST THIS WEEKEND - THE SOUTHERN PIECE AT LEAST.
THE TAIL END OF THE FRONT WILL DRIFT BACK TOWARD THE NORTH ONCE IT
HAS CAUGHT UP W/ THE MINOR UPPER SHORTWAVE OVER THE SRN ATLC COAST.
MOST GUIDANCE MEMBERS KEEP A BULK OF THE SYSTEM AS ITS PRECIP OFF
THE COAST AND IT TRAVELS PARALLEL TO THE NC/DELMARVA COASTLINE EARLY
NEXT WEEK. HOWEVER...THE NRN HEAD OF THE SYSTEM WILL CARRY LOW
CLOUDS FROM THE ONSHORE FLOW AND PERIODS OF VERY LIGHT RAIN AND
DRIZZLE.

THIS TYPE OF SCENARIO KEEPS THE REGION COOL AND MOIST ON MONDAY...W/
A GRADUAL WARM-UP TOWARD THE MIDDLE OF THE WEEK ONCE THE OFFSHORE
SHORTWAVE MOVES AWAY. DIRECTLY ON ITS HEELS HOWEVER IS ANOTHER
FRONTAL PASSAGE LATE WED INTO EARLY THU. AN UPPER RIDGE WILL SQUEEZE
IN BETWEEN SYSTEM ON TUE AND BRIEFLY INTO WED...KEEPING THE AREA DRY
AND PULLING OUR TEMPS BACK INTO THE M-U60S. THE FRONT WILL MOVE
THROUGH W/ THE LOW POSSIBILITY OF CONVECTION AND SOME MODERATE/HEAVY
RAIN BRIEFLY. THE FRONT WON'T TANK TEMPS LIKE THE CURRENT FRONTAL
PASSAGE...ONLY DROPPING THE DAYTIME HIGHS A FEW DEGREES HEADING INTO
THE NEXT WEEKEND - THOUGH IT WILL HELP TO DRY OUT CONDITIONS.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
CIGS HAVE INCREASED TO VFR AT 18Z TODAY OVER ALL TERMINALS. VFR
EXPECTED TO CONTINUE UNTIL SHOWERS/TSTMS REACH THE TERMINALS AHEAD
OF A STRONG COLD FRONT. TSTMS LIKELY WILL BE LATE AFTERNOON/EARLY
EVENING FOR DC METRO TERMINALS. AMENDMENTS EXPECTED TO REFINE
TIMING AND IMPACT. GUSTY SOUTHERLY WINDS WILL CONTINUE...SHIFTING
TO THE W-NW THIS EVENING BEHIND THE FRONT.

HIPRES OVR THE TERMINALS THIS WKND. NW WNDS SAT G20-25KT...BCMG NLY
AND DIMINISHING SAT NGT...AND VEERING ELY SUN.

ONSHORE FLOW DEVELOPS LATE IN THE WEEKEND AS HIPRES SHIFTS OFF THE
NEW ENGLAND COAST. THERE IS A POTENTIAL FOR AN EXTENDED PERIOD OF
LOW CLOUDS AND FOG ERY NEXT WEEK IF ONSHORE FLOW PERSISTS.

&&

.MARINE...
GALE WARNING IN EFFECT OVER ALL WATERS THRU 10PM. SOUTHERLY WINDS
WILL CONTINUE TO GUST IN THE 25-40KT RANGE AHEAD OF AN APPROACHING
COLD FRONT. A LINE OF HEAVY SHOWERS AND THUNDERSTORMS IS EXPECTED
ALONG AND JUST AHEAD OF THE COLD FRONT. THE BEST CHANCE FOR THE
HEAVIER PRECIPITATION OVER THE WATERS WILL BE BETWEEN ABOUT 6 PM
AND MIDNIGHT. THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY
WINDS. SPECIAL MARINE WARNINGS MAY BE NEEDED WITH THESE
THUNDERSTORMS IF WIND GUSTS REACH STORM FORCE.

THE COLD FRONT WILL MOVE OFF TO THE EAST LATE TONIGHT AND WINDS WILL
SHIFT TO THE NORTHWEST. SMALL CRAFT ADVISORIES IN EFFECT OVERNIGHT
FOR THE WATERS...EXCEPT FOR THE WRN ZONES OF THE TP.

THOUGH HIGH PRES WILL BUILD IN BEHIND THE FRONT THIS WEEKEND...
BREEZY NWLY WINDS ON SAT AFTN - MARGINAL SCA RANGE. WINDS WILL
SWITCH TO NELY ON SUN. A STALLED FRONTAL BOUNDARY WILL LIFT BACK
NWD LATE SUN INTO MON...PICKING WINDS BACK UP OVER THE WATERS INTO
SCA RANGE - SUBSIDING MID WEEK W/ ANOTHER APPEARANCE OF HIGH
PRESSURE.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES HAVE HELD STEADY AT AROUND OR JUST ABOVE 1 FT THIS
AFTERNOON...IN SPITE OF THE PERSISTENT SOUTHERLY FLOW. ANNAPOLIS
AND BALTIMORE FELL SHORT OF MINOR FLOODING WITH HIGH TIDE EARLY
THIS AFTERNOON. HIGH TIDE AT WASHINGTON CHANNEL AND ALEXANDRIA
WILL BE BETWEEN 3 AND 4 PM. GIVEN THAT ANOMALIES ARE NOT
INCREASING...WE ARE NOT EXPECTING EITHER TO REACH MINOR FLOODING
IN THIS CYCLE.

DEPARTURES SHOULD BE LOWER FOR THE AM CYCLE SAT...BUT BLOWOUT
CONDS MAY NOT BE REALIZED TIL LATE SAT-SAT NGT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 PM EDT
     SATURDAY FOR ANZ530>534-537>543.
     GALE WARNING UNTIL 10 PM EDT THIS EVENING FOR ANZ530>543.
     SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EDT SATURDAY FOR ANZ535-
     536.

&&

SYNOPSIS...KCS/GMS
NEAR TERM...KCS
SHORT TERM...KCS
LONG TERM...GMS
AVIATION...KCS/HTS
MARINE...KCS/GMS
TIDES/COASTAL FLOODING...KCS

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
409 PM EDT FRI APR 19 2013

MDZ003-502-WVZ050-051-055-502-504-192100-
WASHINGTON MD-MORGAN WV-HARDY WV-HAMPSHIRE WV-
CENTRAL AND EASTERN ALLEGANY MD-EASTERN MINERAL WV-EASTERN GRANT WV-
409 PM EDT FRI APR 19 2013

...SHOWERS WITH GUSTY WIND TO AFFECT WASHINGTON...MORGAN...HARDY...
HAMPSHIRE...CENTRAL AND EASTERN ALLEGANY...EASTERN MINERAL AND
EASTERN GRANT COUNTIES...

AT 409 PM EDT...SHOWERS PRODUCING GUSTY WIND WERE LOCATED ALONG A
LINE EXTENDING FROM 3 MILES SOUTHWEST OF PLEASANT VALLEY TO 3 MILES
SOUTHWEST OF RIG...MOVING EAST AT 30 MPH.

LOCATIONS IMPACTED INCLUDE MOOREFIELD...ROMNEY...LARGENT AND FISHERS
BRIDGE.

WIND GUSTS OF 40 TO 50 MPH CAN BE EXPECTED WITH THESE SHOWERS.

&&

LAT...LON 3972 7818 3894 7868 3901 7918 3973 7873
TIME...MOT...LOC 2009Z 269DEG 26KT 3968 7864 3901 7905

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
433 PM EDT FRI APR 19 2013

VAZ036-037-192115-
NELSON VA-ALBEMARLE VA-
433 PM EDT FRI APR 19 2013

...STRONG THUNDERSTORMS TO AFFECT NELSON AND ALBEMARLE COUNTIES...

AT 433 PM EDT...STRONG THUNDERSTORMS WERE LOCATED ALONG A LINE
EXTENDING FROM 17 MILES WEST OF PINEY RIVER TO 34 MILES SOUTHWEST OF
ALLENS CREEK...MOVING EAST AT 50 MPH.

LOCATIONS IMPACTED INCLUDE SHIPMAN AND SCHUYLER.

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

WIND GUSTS IN EXCESS OF 50 MPH ARE EXPECTED WITH THESE STORMS. WINDS
THIS STRONG CAN BRING DOWN LARGE TREE BRANCHES. TAKE SHELTER UNTIL
THE STORMS HAVE PASSED.

&&

LAT...LON 3755 7891 3769 7899 3772 7907 3778 7909
      3780 7917 3783 7916 3792 7839 3775 7851
      3774 7863 3768 7864 3767 7866 3769 7869
      3763 7872 3764 7880 3763 7881 3758 7883
      3756 7881 3753 7883
TIME...MOT...LOC 2033Z 262DEG 44KT 3770 7929 3719 7924

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
502 PM EDT FRI APR 19 2013

MDZ003-VAZ028-WVZ050>053-192145-
WASHINGTON MD-MORGAN WV-JEFFERSON WV-HAMPSHIRE WV-BERKELEY WV-
FREDERICK VA-
502 PM EDT FRI APR 19 2013

...STRONG THUNDERSTORM TO AFFECT WASHINGTON...MORGAN...JEFFERSON...
HAMPSHIRE...BERKELEY AND FREDERICK COUNTIES...

AT 502 PM EDT...A STRONG THUNDERSTORM WAS LOCATED OVER SLANESVILLE...
MOVING EAST AT 50 MPH.

LOCATIONS IMPACTED INCLUDE RIDGE...LARGENT...GREENWOOD...VALLEY
HIGH...ROCK GAP...AND MARTINSBURG.

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

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

&&

LAT...LON 3966 7794 3945 7783 3926 7853 3943 7861
TIME...MOT...LOC 2102Z 248DEG 44KT 3939 7844

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
515 PM EDT FRI APR 19 2013

VAZ036-037-192145-
NELSON VA-ALBEMARLE VA-
515 PM EDT FRI APR 19 2013

...STRONG THUNDERSTORM TO AFFECT NELSON AND ALBEMARLE COUNTIES...

AT 515 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 3 MILES SOUTHEAST
OF NELLYSFORD...MOVING NORTHEAST AT 55 MPH.

LOCATIONS IMPACTED INCLUDE SCOTT STADIUM.

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

WIND GUSTS IN EXCESS OF 50 MPH ARE EXPECTED WITH THIS STORM. WINDS
THIS STRONG CAN BRING DOWN LARGE TREE BRANCHES. TAKE SHELTER UNTIL
THE STORM HAS PASSED.

&&

LAT...LON 3819 7849 3806 7834 3777 7881 3791 7895
TIME...MOT...LOC 2115Z 230DEG 52KT 3790 7878

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
517 PM EDT FRI APR 19 2013

VAZ026-029-037>039-192145-
GREENE VA-MADISON VA-PAGE VA-ROCKINGHAM VA-ALBEMARLE VA-
517 PM EDT FRI APR 19 2013

...STRONG THUNDERSTORM TO AFFECT GREENE...MADISON...PAGE...ROCKINGHAM
AND ALBEMARLE COUNTIES...

AT 516 PM EDT...A STRONG THUNDERSTORM WAS LOCATED 5 MILES SOUTHWEST
OF MISSION HOME...MOVING NORTHEAST AT 55 MPH.

LOCATIONS IMPACTED INCLUDE STANARDSVILLE AND MADISON.

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

WIND GUSTS IN EXCESS OF 50 MPH ARE EXPECTED WITH THIS STORM. WINDS
THIS STRONG CAN BRING DOWN LARGE TREE BRANCHES. TAKE SHELTER UNTIL
THE STORM HAS PASSED.

&&

LAT...LON 3856 7835 3831 7820 3811 7872 3830 7877
TIME...MOT...LOC 2116Z 230DEG 52KT 3827 7865