Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 310116
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
916 PM EDT SAT AUG 30 2014

.SYNOPSIS...
HIGH PRESSURE OFF CAPE COD WILL MOVE SOUTHEAST AND BECOME A
BERMUDA HIGH THROUGH TUESDAY. A COLD FRONT WILL CROSS THE AREA
TUESDAY NIGHT. HIGH PRESSURE WILL FOLLOW FOR THE SECOND HALF OF
THE WEEK.

&&

.NEAR TERM /THROUGH SUNDAY/...
AT 01Z KLWX RADAR SHOWING THE LINE OF THUNDERSTORMS THAT TRAVERSED
THE POTOMAC HIGHLANDS EARLIER THIS EVENING DISSIPATING. ONE AREA
OF SHOWERS/TSTMS REMAINS OVER THE BLUE RIDGE NEAR WAYNESBORO.
THIS TOO APPEARS TO BE DISSIPATING AS IT MOVES NORTHEAST.

SKIES WILL BE PARTLY TO MOSTLY CLOUDY TONIGHT AS MID AND HIGH
CLOUDS FROM THE CONVECTION OVER THE TN VALLEY CONTINUES TO STREAM
TO THE NORTHEAST. WITH HIGH DEWPOINTS...WILL SEE AREAS OF FOG
DEVELOPING...PREDOMINANTLY IN SHELTERED LOCATIONS WHERE LIGHT
SOUTHERLY WINDS WILL NOT BE ABLE TO MIX THE BOUNDARY LAYER. AT
01Z...ALREADY SEEING LOW SFC TEMP/DWPT SPREADS AT STAFFORD AND
WARRENTON AND MIST FORMING. BOTH MET AND MAV GUIDANCE SHOWS VSBYS
LOWERING OVERNIGHT.

SUNDAY WILL START OUT WITH LINGERING PATCHY FOG THROUGH MID
MORNING...THEN REMAIN MOSTLY CLOUDY. THE 18Z GFS HAS A STREAK OF
PRECIP WATER GREAT THAN 2.25" ACROSS OUR CWA AS A POTENT H5 VORT
TRACKS FROM SW. THIS WILL LEAD TO NUMEROUS SHRA/TSTMS DEVELOPING
BY MID AFTERNOON AND LASTING THROUGH MIDNIGHT. SOME OF THESE
STORMS WILL HAVE THE POTENTIAL TO PRODUCE HEAVY RAINFALL...BUT
THERE IS DECENT 20-30 KTS IN THE CLOUD BEARING LAYER WHICH WILL
KEEP THE STORMS PROGRESSIVE.


&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
CWFA WL BE W/IN SWLY FLOW FOR THE FRIST PARTS OF THE WK. HWVR THE
FLOW WL BECOME A BIT MORE WLY MON...AND SPCLY TUE. THE PLUME OF
MSTR EVIDENT ON WATER VAPOR IMGRY WL BE RUNNING ATOP THE RDG.

LTST GDNC SUGGESTING THAT THE SETUP WONT BE QUITE AS IDEAL AS
PRVS CYCLES. THATS NOT TO SAY THERE WONT BE A MOIST/UNSTBL AMS.
BUT THTE RDG/ADVTN AS WELL AS PVA DURING THE AFTN WL BE BETTER IN
THE MTNS AND PTS WEST. STILL WL HV A CORRIDOR OF PWAT AOA 2
INCHES...BUT THERE/S NOT AS MUCH TO ORGANIZE/FORCE THE PCPN. AND
IN THE SERN CWFA...RDGG WL ACTUALLY SURPRESS IT. HV THEREFORE
BACKED OFF ON POPS SUN...STILL FOCUSING ON THE AFTN-EVE HRS. LKLY
POPS WONT APPEAR TIL EVNG...WHEN LIFT ARRIVES. NOCTURNAL STABILITY
WL ALLOW PVA TO SNEAK THRU OVNGT.

AM FCSTG A GOOD DEAL OF CLDCVR SUN...WHICH SHUD ONCE AGN IMPEDE
STRONG WARMING. HV SHADED DOWN MAXT A DEGF OR TWO.

WHILE THERE WL BE A SHARP LEE TROF MON...ALL OTHER FEATURES APPEAR
TO BE EITHER WEAK OR SUBTLE. WLY FLOW WL PROVIDE A LTL BIT OF
DRYING...WHICH IS EVIDENT IN PROGGED PWAT VALUES. THE IMPACT IS
EVIDENT IN POP VALUES...WHICH ARE LWR THAN SUN. THAT SEEMS QUITE
RESONABLE. AM GNLY IN THE 30-40 PCT RANGE...AND AM KEEPING A DRY
FCST IN CENTRL VA. WHATEVER TSRA THAT DO DVLP SHUD MV TO THE ERN
SHORE BY NIGHTFALL...AND HV A DRY FCST FOR MON NGT-- WHICH LARGELY
WL CONT INTO TUE DUE TO DOWNSLOPING.

THINK THAT THE BEST CHC AT A 90 DEG DAY WL COME ON TUE...AS WLY
FLOW WL KEEP POPS LOW AND PROVIDE COMPRESSIONAL WARMING. HV LWRD
MON MAXT BY A CPL...AND RAISED TUE MAXT ALSO BY A CPL. MIN-T FCSTS
ON TRACK...IN STEP W/ PROGGED DEWPTS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
500MB SHORTWAVE WILL TRACK FROM THE GREAT LAKES TO SOUTHERN QUEBEC
AND DRAG A WEAK TROUGH THROUGH THE CWA TUESDAY NIGHT THROUGH
WEDNESDAY. 500MB HIGH WILL BUILD OVER MID ATLANTIC REGION WEDNESDAY
THROUGH THURSDAY. THE HIGH WILL WEAKEN ALLOWING A COLD FRONT TO
ENTER NORTHWEST PA BY SATURDAY NIGHT.

BAND OF MOISTURE...PVA...AND PASSAGE OF THE COLD FRONT WILL SUPPORT
A SLIGHT CHANCE DEVELOPMENT OF SHOWERS/THUNDERSTORMS TUESDAY NIGHT
THROUGH WEDNESDAY MORNING. MUCH DRIER AIRMASS ASSOCIATED WITH
SURFACE HIGH WILL CROSS THE CWA LATER WEDNESDAY THROUGH EARLY FRIDAY.
INCREASING MOISTURE DUE TO THE RETURN SOUTH TO SOUTHWEST FLOW
ASSOCIATED WITH THE HIGH AND PVA OUT AHEAD OF AN APPROACHING COLD
FRONT FROM THE WEST WILL SUPPORT AN INCREASED CHANCE OF MORE SHOWERS
AND THUNDERSTORMS SATURDAY.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...

SLY FLOW WL PROVIDE INCREASING LOW LVL HUMIDITY. THEREFORE...
OVERNIGHT FOG SHUD BE AN ISSUE. FLLWG CLIMO BY KEEPING DCA AT VFR.
OTRW...HV MVRG VSBYS ACRS THE BOARD PRE-DAWN. IFR A PSBLTY...BUT
THINK THERE WL BE TOO MUCH HIER LVL CLDCVR FOR THICKER FOG TO DVLP.

ONCE MRNG RESTRICTIONS CLR...ATM WL BE UNSTBL FOR SCT TSRA TO
DVLP. CUD HV LCL IFR IN HVR RAINERS...BUT LOW CONFIDENCE IN A SPOT
FCST PRECLUDE A TAF INCLUSION.

OUTLOOK...SUNDAY NIGHT SHOULD SEE MVFR FOG RETURN AFTER
RAINFALL...THEN MON TARGETED IFR POSSIBLE AT TIMES WITH SCT TSRA.
CVRG SHUD BE LESS THAN SUN. TUE-THU...PRIMARILY VFR.

&&

.MARINE...
SLY FLOW ACRS THE MARINE AREA THRU THE WKND. SCA IN EFFECT
OVERNIGHT FOR BAY SANDY PT-SMITH PT AS INDICATED BY 01Z MARINE OBS
OF UPPER TEEN GUSTS. IT/LL BE A SIMLR SITUATION SUNDAY...THO DONT
THINK THE MIXING WL BE QUITE AS GOOD. IN ADDITION...POTL TSRA WUD
PROVIDE STRONGER WIND GUSTS.

OFFSHORE HIGH PRES WILL CONTINUE TO STEER WARM/HUMID AIR UP ACROSS
THE ERN SEABOARD. SETUP WUD SUPPORT PDS OF SLY CHANNELING...BUT
GDNC NOT PICKING UP ON ANY JUST YET. WK CDFNT LT TUE/ELY WED...
MARKED BY A SLGT SHIFT IN WIND DIRECTION FM SW TO NW.

&&

.TIDES/COASTAL FLOODING...
DEPARTURES AT ANNAPOLIS ARE ABOUT 0.9 FEET...AND WINDS SHOULD REMAIN
SLY...SO ANTICIPATE ADDTL INCREASES THROUGH THE WKND. BARELY MADE
IT TO 2.4 FT AT 0030Z...SO MISSED A MINOR THIS EVENING.  THE NEXT
HIGH TIDE SUN MRNG WL NEED TO BE WATCHED FOR POSSIBLE MINOR
FLOODING. NONETHELESS...THIS WL BE AN ISSUE THROUGH THE WKND WITH
NEW MOON AND SOUTHERLIES.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT SUNDAY FOR ANZ532>534.

&&

$$
SYNOPSIS...HTS
NEAR TERM...LEE
SHORT TERM...HTS
LONG TERM...CEM
AVIATION...HTS/LEE
MARINE...HTS/LEE
TIDES/COASTAL FLOODING...HTS/LEE






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