FXUS61 KLWX 231357
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
957 AM EDT THU MAY 23 2013

.SYNOPSIS...
A COLD FRONT WILL APPROACH AREA TODAY BEFORE CROSSING TONIGHT. AN
UPPER-LEVEL LOW PERSISTS OVER THE REGION FRIDAY AND SATURDAY.
CANADIAN HIGH PRESSURE WILL BUILD OVERHEAD FOR THE MEMORIAL DAY
WEEKEND. A WARM FRONT WILL PASS THROUGH THE AREA DURING THE
MIDDLE PORTION OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
EXTENSIVE CLOUD COVER REMAINS ACROSS THE MID-ATLANTIC AT 13Z.
HOWEVER...AM ALREADY STARTING TO SEE BREAKS IN THE CLOUDS OVER
PORTIONS OF SOUTHERN AND CENTRAL VIRGINIA...AND ALSO INTO WEST
VIRGINIA AND EXPECT THESE BREAKS TO WORK INTO THE CWA LATER ON
THIS AFTERNOON. THESE BREAKS WILL ALLOW WARMING TO TAKE
PLACE...BOOSTING MAXIMA AOA 80F ESPECIALLY EAST OF THE BLUE RIDGE. 

UP TIL NOON...THERE WILL BE SCATTERED SHOWERS OVER THE CWA. BUT
WITH EXPECTED HEATING...EXPECT TO SEE AN UPTICK IN COVERAGE OF
CONVECTION INCLUDING THUNDERSTORMS BETWEEN NOON AND 2 PM.
APPROACHING UPPER SHORTWAVE AND SURFACE TROUGH WILL HELP TO SERVE
AS INITIAL TRIGGERS /FRONTAL BOUNDARY MAY ALSO BE A TRIGGER LATER
ON/. MODIFIED 12Z KIAD RAOB FOR 80/65 INDICATES OVER 1500 J/KG OF
MOST UNSTABLE CAPE...MIXED LAYER IS LESS THAN 1000 BUT SUFFICIENT. 

IN ADDITION...WIND FIELDS BECOME MORE FAVORABLE AS THE DAY
PROGRESSES WHICH WILL ENHANCE SHEAR. COMBINATION OF INSTABILITY
AND SHEAR IS EXPECTED TO HELP ORGANIZE STORMS INTO MULTICELL
CLUSTERS...SOME OF WHICH MAY PRODUCE DAMAGING WIND GUSTS AND
PERHAPS SOME LARGE HAIL. 

SEVERITY OF STORMS SHOULD WANE AFTER SUNSET...BUT THE FRONTAL
BOUNDARY ITSELF WILL LIKELY KEEP AT LEAST SCATTERED CONVECTION
GOING WELL INTO THE EVENING. 

TEMPS BEHIND THE FRONT WILL BE NOTICEABLY COOLER ACROSS WESTERN
PORTIONS OF THE CWA. HOWEVER...THE COOLER AIR MAY NOT ARRIVE UNTIL
FRIDAY FOR LOCATIONS EAST OF THE BLUE RIDGE MOUNTAINS. MIN TEMPS
WILL RANGE FROM THE 40S IN THE ALLEGHENY HIGHLANDS TO THE MID 60S
IN WASHINGTON/BALTIMORE.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
CLOSED UPR LOW NOW PROGGED TO DRIFT EAST OVER THE CENTRAL MID 
ATLANTIC FRIDAY BEFORE DRIFTING UP TO NEW ENGLAND THROUGH THE 
WEEKEND. CONFIDENCE IS LOW ON EXACT PLACEMENT OF THIS LOW. WILL 
PROBABLY UPDATE THE FORECAST WITH THE 00Z ECMWF WHICH IS 
FORTHCOMING. THIS COLD CORE WILL BRING INSTABILITY SHOWERS TO THE 
AREA FRIDAY INTO (UNCERTAIN HOW FAR INTO) SATURDAY WITH GUSTY NWLY 
FLOW (GUSTS AROUND 30 MPH)...CLOUDY SKIES...AND MUCH BELOW NORMAL 
TEMPERATURES. SHOULD BE PRETTY SIMILAR TO LAST SATURDAY IT DROPPED 
TO AROUND 60F ONCE THE INTERMITTENT SHOWERS GOT GOING. 

LOW/TROUGH TAKES ON A NEGATIVE TILT SATURDAY WHICH SHOULD SHUNT THE 
LOW OFF THE MID-ATLANTIC COAST. NWLY FLOW CONTINUES TO GUST 25 TO 30 
MPH. OUR GRIDS DO NOT INDICATE A WIND CHILL...BUT IF IT IS PRETTY 
CLOUDY AND THAT WINDY THERE WOULD CERTAINLY BE A CHILL.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
WITH THE UPR LOW MERELY DRIFTING TO NEW ENGLAND THROUGH SUNDAY...THE 
SHORTWAVE OVER THE TN VLY LOOKS CONTAINED/AWAY FROM THE CENTRAL 
MID-ATLANTIC UNTIL PERHAPS TUESDAY. WITH CANADIAN AIRMASS IN 
PLACE...EXPECT A STEADY WARMING TREND DUE TO MODIFICATION BY THE 
STRONG LATE MAY SUN.

WARM FRONT LIFTS NORTH ACROSS THE REGION MID NEXT WEEK WITH 
THUNDERSTORM CHANCES AND A RETURN OF SEASONABLY WARM CONDITIONS.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
MVFR CIGS NEAR DCA/BWI WILL IMPROVE ABV 3K FT BY 15Z...LEAVING
PREVAILING VFR FOR THE REST OF THE DAY. HOWEVER...FLIGHT
RESTRICTIONS IN SHRA/TSRA CAN BE EXPECTED DURING THE
AFTERNOON/EARLY EVENING. THUNDERSTORMS WILL BE CAPABLE OF
PRODUCING GUSTY WINDS AND HAIL AS WELL. A COLD FRONT WILL PASS
THROUGH THE TERMINALS LATE TONIGHT WITH A WIND SHIFT. GUSTY WINDS
EXPECTED FRIDAY. 

NWLY FLOW WITH GUSTS 25 TO POSSIBLY 30 KT WITH PSBL MVFR CIGS AND 
OCCASIONAL SHOWERS FRIDAY UNDER AND UPR LOW. STRONG NWLY FLOW 
CONTINUES THROUGH SATURDAY AS THE UPR LOW REMAINS IN THE REGION AND 
SFC HIGH PRESSURE BUILDS. VFR EARLY NEXT WEEK IN A CANADIAN AIRMASS 
BEFORE A MIDWEEK WARM FRONT.

&&

.MARINE...
A SOUTHERLY FLOW WILL CONTINUE AROUND HIGH PRESSURE TODAY. A SMALL
CRAFT ADVISORY IS IN EFFECT FOR THE WATERS. SHOWERS AND
THUNDERSTORMS WILL INCREASE IN COVERAGE THIS AFTERNOON AND
EVENING. SOME THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY
WINDS AND HAIL. SPECIAL MARINE WARNINGS MAY BE WARRANTED.

A COLD FRONT WILL APPROACH THE WATERS TONIGHT. A LULL IN THE
PRESSURE GRADIENT SUGGESTS THAT WIND SPEEDS MAY BE BELOW SCA
CRITERIA. 

NWLY FLOW WITH GUSTS 25 TO 30 KT FRIDAY THROUGH SATURDAY AS AN UPR 
LOW PERSIST OVER THE REGION AND SFC HIGH PRESSURE BUILDS. SCA IN 
EFFECT FOR FRIDAY...EXPECT IT TO BE EXTENDED INTO SATURDAY NIGHT. 
MORE TRANQUIL WEATHER EARLY NEXT WEEK UNDER A CANADIAN AIRMASS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
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 FRIDAY FOR 
     ANZ530>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BPP/BJL
SHORT TERM...BAJ
LONG TERM...BAJ
AVIATION...BPP/BJL/BAJ
MARINE...BPP/BJL/BAJ