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FXUS61 KLWX 150803
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
403 AM EDT TUE APR 15 2014

.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE THROUGH THE MID-ATLANTIC REGION FROM 
THE WEST TODAY. HIGH PRESSURE WILL MOVE NORTHEAST ACROSS THE 
NORTHERN MID-ATLANTIC WEDNESDAY...WITH COLD AIR DAMMING LINGERING 
UNTIL LOW PRESSURE AFFECTS THE REGION ON SATURDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
PRIMARY WX PLAYER FOR THE MID-ATLANTIC REGION IS A STRONG COLD FRONT 
THAT WILL MOVE THRU THE AREA TDA. THIS FRONT WAS LOCATED ON THE WRN 
SIDE OF THE APPALACHIANS AT 07Z AND IS MARKED BY A SHARP TEMP 
GRADIENT AND WIND SHIFT FROM S TO NW. 

STRONG SLY WINDS AND A DEEP POLEWARD MOISTURE TRANSPORT IN 
PRE-FRONTAL WARM SECTOR HAVE RESULTED IN TEMPS IN MILD AND MOIST 
CONDITIONS ACROSS THE CWA. UPSTREAM COVERAGE OF SHOWERS HAVE 
INCREASED OVER WRN NC/SWRN VA IN THE PAST FEW HRS AND WILL EXPAND 
INTO THE CWA FROM SW TO NE THRU THE MRNG. EXPECT WIDESPREAD SHOWERS 
ALONG AND WEST OF I-95 FOR MUCH OF THE MRNG. THERE IS VERY LITTLE 
INSTABILITY OVER THE AREA RIGHT NOW BUT INSTABILITY WILL INCREASE 
LATER THIS MRNG AND THIS AFTN AHEAD OF THE FRONT AS LLVL THETA-E 
RIDGE PROGRESSES NWD. DESPITE SBCAPE VALUES ONLY AROUND 500 J/KG AS 
SEEN ON THE LATEST NAM/RAP SOUNDINGS...STRONG WIND FIELD ALOFT WILL 
SUPPORT THE POTENTIAL FOR LOCALLY DAMAGING WINDS WITH ANY LOW-TOPPED 
CONVECTION THAT DEVELOPS. A LINEAR MODE OF CONVECTION WOULD BE 
FAVORED WITH THIS SETUP. IF CONVECTION DOES BECOME ORGANIZED...0-3 
KM SHERB VALUES ABOVE 1 INDICATE THE POTENTIAL FOR DAMAGING WINDS 
ALONG AND EAST OF THE BLUE RIDGE LATE THIS MRNG AND ERY THIS AFTN. 
DAY 1 OUTLOOK FROM SPC HAS US IN A 5 PERCENT RISK OF DAMAGING WINDS. 
LOCALLY HEAVY RAINFALL WILL ALSO BE POSSIBLE TDA. LOCALLY HVY 
RAINFALL AMOUNTS AROUND 2 INCHES ARE POSSIBLE...AND COULD CAUSE SOME 
ISO FLOODING PROBLEMS IN POOR DRAINAGE AREAS.

THE COLD FRONT WILL MOVE THRU THE MTS THIS MRNG AND EAST OF THE BLUE 
RIDGE THIS AFTN. A SHARP TEMP DROP WILL OCCUR BEHIND THE FRONT AS  
UNSEASONABLY COLD AIR MOVES IN. IT WILL ESSENTIALLY FEEL LIKE A 
CHANGE IN SEASONS FROM LATE SPRING AHEAD OF THE FRONT TO MORE LIKE 
WINTER IN LESS THAN 12 HOURS. A SIGNIFICANT POST-FRONTAL PRESSURE 
SURGE AND STRONG CAA WILL PRODUCE GUSTY WINDS.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
WEDNESDAY...HIGH PRESSURE BUILDS NORTHEAST ACROSS THE NRN 
MID-ATLANTIC...BECOMING A 1045 MB OR SO SFC HIGH OVER NEW ENGLAND
WEDNESDAY NIGHT. MAX TEMPS AROUND 50F ARE 15 OR SO DEGREES BELOW
NORMAL. SUNNY WITH PERHAPS SOME WISPY CIRRUS IN THE AFTERNOON
OVERRUNNING A LOW AMPLITUDE RIDGE TO OUR WEST. STRONG NWLY GUSTS
IN THE MORNING EASE THROUGH MIDDAY. PARTIAL DECOUPLING WEDNESDAY
NIGHT WITH MIN TEMPS AROUND 30F INLAND...MID TO UPR 30S URBAN AND
NEARSHORE. FREEZE WARNING LIKELY NEEDED...THOUGH MAYBE NOT FOR ALL
ZONES EAST OF THE BLUE RIDGE LIKE TONIGHT.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
SFC PRESSURE RIDGE/COLD AIR DAMMING PERSISTS WEDNESDAY NIGHT INTO 
SATURDAY...WHEN THE NEXT DISTURBANCE DISLODGES THE ONSHORE FLOW. 
EXPECT BELOW NORMAL TEMPS TO CONTINUE WITH THE ONSHORE FLOW. AREAS 
EAST OF THE RIDGE AXIS BECOME SATURATED BY FRIDAY WITH DRIZZLE OR 
LIGHT RAIN POSSIBLE THEN THROUGH FRIDAY NIGHT. UNCERTAINTY ON 
SOUTHWARD EXTEND OF THE UPPER TROUGH MOVING WEST ACROSS THE NERN 
CONUS ON SATURDAY. CURRENTLY THE 00Z GFS IS MORE AMPLIFIED THAN THE 
00Z ECMWF. THE COOL PATTERN CONTINUES THROUGH AT LEAST SUNDAY AS 
CANADIAN HIGH PRESSURE BUILDING IN BEHIND THE SATURDAY SYSTEM.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
MVFR CIGS AND VSBYS PREVAIL THROUGH THE DAY WITH INTERMITTENT IFR
IN HEAVIER RAIN. ISO THUNDER THREAT TODAY. SLY FLOW GUSTS UP TO
30 KT AHEAD OF THE COLD FRONT APPROACHING FROM THE WEST. STRONG
COLD FRONT CROSSES THE TERMINALS LATE THIS MORNING THROUGH THE
EARLY AFTERNOON WITH A QUICK NWLY WIND SHIFT. GUSTS TO 35 KT LATE
THIS AFTERNOON THROUGH TONIGHT ACROSS THE TERMINALS WITH A FEW
SNOWFLAKES AT END OF PRECIP WEST OF BALT-WASH CORRIDOR.

VFR WEDNESDAY AS HIGH PRESSURE BUILDS NORTHEAST ACROSS THE REGION 
WEDNESDAY. GUSTY NW WINDS EASE THROUGH MIDDAY. ONSHORE FLOW FROM 
COLD AIR DAMMING RIDGE THEN INTO SATURDAY WHEN THE NEXT LOW PASSES 
THE REGION. SUB-VFR CONDS POSSIBLY SPREAD FROM THE EAST FRIDAY AS 
THE ONSHORE FLOW SATURATES.

&&

.MARINE...
SLY SCA LEVEL WINDS ACROSS THE WATERS. HOWEVER...AT 6AM THE SCA
UPGRADES TO A GALE WARNING TO ACCOUNT FOR POSSIBLE SLY GALES IN
RAIN LATER THIS MORNING...AS WELL AN EXPECTED 4PM ONSET OF NWLY
GALES BEHIND THE COLD FRONT. GALE WARNING THROUGH TONIGHT WITH 40
KT POSSIBLE OVER ALL OF THE WATERS.

GALES POSSIBLE FOR LOWER SRN MD WATERS EARLY WEDNESDAY MORNING...BUT 
BUT HAD CONFIDENCE TO SIMPLY ISSUE AN SCA FOR ALL WATERS UNTIL
3PM AND MD BAY WATERS UNTIL 6PM WEDNESDAY AS HIGH PRESSURE BUILDS
NORTHEAST ACROSS THE REGION. ONSHORE FLOW THEN OVER THE REGION
INTO SATURDAY. ELY FLOW 15 TO 20 KT/SCA LIKELY FOR THURSDAY.

&&

.TIDES/COASTAL FLOODING...
NWLY GALES TUESDAY NIGHT AND STRONG SCA WINDS INTO WEDNESDAY 
AFTERNOON WILL CAUSE BLOWOUT TIDE CONDITIONS FOR THE LOW TIDES ON 
WEDNESDAY. OF PARTICULAR CONCERN IS THE MIDDAY/AFTERNOON LOW TIDE 
CYCLE WHERE WATER LEVELS LOOK TO DROP TO AROUND 2 FEET BELOW MLLW.

&&

.CLIMATE...
RECORD DAILY HIGH MINIMUM TEMPERATURES WERE SET FOR DCA AND IAD...
AND TIED FOR BWI. BELOW IS A TABLE OF RECORDS FOR APRIL 14 AND LOW
TEMPERATURES OBSERVED.

SITE...PREV RECORD......LOW...
DCA....63F IN 1896......65F...
BWI....62F IN 1896......62F...
IAD....58F IN 1972......63F...

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR DCZ001.
MD...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR MDZ011-013-
     014-016>018.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR 
     MDZ004>007-009-010.
VA...FREEZE WARNING FROM 3 AM TO 9 AM EDT WEDNESDAY FOR VAZ052>057.
     FREEZE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EDT WEDNESDAY FOR 
     VAZ036>040-042-050-051-501-502.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR 
     ANZ530>543.
     SMALL CRAFT ADVISORY FROM 6 AM TO 6 PM EDT WEDNESDAY FOR 
     ANZ531>534-537-539>541-543.
     GALE WARNING FROM 6 PM THIS EVENING TO 6 AM EDT WEDNESDAY FOR 
     ANZ530>543.
     SMALL CRAFT ADVISORY FROM 6 AM TO 2 PM EDT WEDNESDAY FOR 
     ANZ530-535-536-538-542.

&&

$$
SYNOPSIS...BAJ/JRK
NEAR TERM...JRK
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BAJ
MARINE...BAJ
TIDES/COASTAL FLOODING...BAJ
CLIMATE...BAJ






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