FXUS61 KLWX 211859
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
259 PM EDT TUE MAY 21 2013

.SYNOPSIS...
HIGH PRESSURE OVER THE ATLANTIC WILL CONTINUE TO AID A SOUTHERLY
FLOW THROUGH THURSDAY...BRINGING WARM AND HUMID CONDITIONS.
AFTERNOON AND EVENING THUNDERSTORMS ARE POSSIBLE EACH DAY. A
COLD FRONT WILL PASS THROUGH THE REGION THURSDAY NIGHT INTO
FRIDAY. COOLER CONDITIONS ARE EXPECTED OVER THE WEEKEND.
&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
H5 TROF HAS WEAKENED AND SLID SE OF CWFA. THAT LEAVES CWFA W/IN
SLY FLOW FM RDGG SFC-H5. AMS REMAINS UNSTBL BUT CAPPED...W/ SHEN
VLY/PTMC HIGHLANDS LKLY NEAREST CONVECTIVE TEMPS IN THE UPR 80S.
FORTUNATELY SEE NO SIGNS OF DVLPMNT THRU THE OHVLY...AND HV SCALED
POPS BACK BY ABT 10 PCT. AM STILL HOLDING ONTO CHC POPS SINCE WERE
CLOSE TO BREAKING CAP IN THE W...AND THERE/S PLENTY OF CAPE TO
FEED OFF OF ONCE WE DO. ANY ACTIVITY WL BE FAIRLY UNORGANIZED...
SINCE TRRN CURCULATIONS/DIFF HEATING BNDRYS WL BE BEST TRIGGERS.

ONCE DAYTIME HEATING WANES...RISK DIMINISHES...AND HV SCALED BACK
POPS FOR THE OVNGT HRS. DEWPTS HIGH ENUF THAT W/ PARTLY CLR SKIES
PATCHY FOG SHUD DVLP.
&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/...
CWFA WL BE WARM SECTOR THRU PD...AS SFC HIGH WELL OFF ERN SEABOARD
AIDS SLY FLOW/MOISTURE ADVECTION. THUS AMS WL REMAIN UNSTBL...W/
POPS GNLY INCREASING IN RESPONSE TO DROPPING MID LVL HGTS. WL STILL
HV A DIURNAL TREND TO STORMS. THU LOOKS TO BE THE BETTER DAY IN
TERMS OF TSRA DVLPMNT AS CDFNT/UPR LOW DROPS THRU GRTLKS. HV
RAISED POPS BOTH DAYS AND INTRODUCED LKLYS ON THU.
&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
CFP THU NGT. CANADIAN HIGH PRESSURE BUILDS IN WITH TEMPS 5-10
DEGREES BELOW NORMAL. SHORTWAVE OVER THE TN VLY ON SUNDAY SHOULD
REMAIN WEST OF THE LWX CWA...WILL HAVE TO MONITOR FOR INCREASED
POPS. AS OF NOW EXPECT SOME HIGH CLOUDS SUNDAY WITH A WARMING
TREND STARTING THAT CONTINUES INTO MID NEXT WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
LOW-LEVEL MOISTURE HAS FINALLY SCOURED OUT...LEAVING VFR CONDS AT
ALL TERMINALS. ISOLD SHOWERS AND T-STORMS ARE STILL POSSIBLE THIS
AFTERNOON AND EVENING...PARTICULARLY FOR MRB/CHO...BUT THREAT WAY
TOO SLIM FOR TAF INCLUSION. XPCT AREAS OF LOW CLOUDS/FOG TO DVLP
AGN LT TNGT...CONTG INTO THE WED MRNG PUSH. THIS TIME HV LEANED
MORE TWD FOG DVLPMNT INLAND SINCE SKIES WL BE PRTLY CLR SUPPORTING
RADL COOLING DOWN TO MOIST DEWPTS. HWVR LOW CLDS WL BE LURKING
JUST E OF DCA/BWI.

DIURNAL THUNDERSTORM ACTIVITY WED/THUR WITH IFR CONDS POSSIBLE IN 
THE HEAVIEST ONES. SLY FLOW UNTIL A COLD FROPA THURSDAY NIGHT. NWLY 
FLOW WITH CLEAR CONDS SATURDAY. JUST SOME HIGH CLOUDS ON SUNDAY.

&&

.MARINE...
THE PRESSURE GRADIENT WILL STRENGTHEN OVER THE REGION WED AFTN AND 
NGT AS LOPRES MOVES THRU THE GREAT LAKES AND HIPRES REMAINS PARKED 
OVER THE WRN ATLANTIC. SLY RETURN FLOW WILL INCREASE ACCORDINGLY 
BETWEEN BOTH SYSTEMS. A SCA GOES IN EFFECT WED AFTN FOR THE WATERS 
THAT ARE MOST PRONE TO SLY CHANNELING IN THE MID CHSPK BAY AND 
LWR/MID TIDAL POTOMAC RVR. SCA EXPANDS WED NGT TO INCLUDE ALL OF THE 
MD CHSPK BAY AS A SLY NOCTURNAL JET DEVELOPS.

SLY FLOW WITH HIGH PRESSURE OFFSHORE AHEAD OF A COLD FRONT THAT 
COMES THROUGH THURSDAY NIGHT. SLY CHANNELING TO 20 KT POSSIBLE WED 
EVENING...AND THURSDAY. NWLY FLOW TO 20 KT POSSIBLE FRIDAY. LIGHT 
AND VARIABLE FLOW THIS WEEKEND.

&&

.TIDES/COASTAL FLOODING...
DESPITE SLY WINDS...WATER LEVELS THIS AFTN ARE NEAR ASTRONOMICAL 
TIDE AND EVEN A FEW INCHES BELOW NORMAL IN THE TIDAL POTOMAC. DO 
EXPECT POSITIVE TIDAL ANOMALIES TO DEVELOP DURING THE MIDWEEK AS SLY 
FLOW STRENGTHENS. CBOFS GUIDANCE...WHICH HAS VERIFIED FAIRLY WELL OF 
LATE...FCST WATER LEVELS TO STAY COMFORTABLY BELOW MINOR COASTAL 
FLOODING THRESHOLDS THRU AT LEAST THU MRNG. 

COLD FRONT MOVES THRU ERY FRI MRNG. WLY WINDS BEHIND THE FRONT 
SHOULD ERASE ANY POSITIVE TIDAL ANOMALIES.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 9 PM WEDNESDAY TO 6 AM EDT THURSDAY 
     FOR ANZ530-531-539.
     SMALL CRAFT ADVISORY FROM 2 PM WEDNESDAY TO 6 AM EDT THURSDAY 
     FOR ANZ532>534-536-537-540>543.

&&

$$