Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 291610
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1210 PM EDT SUN MAR 29 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE IN TODAY...FOLLOWED BY A COLD FRONT ON
MONDAY. A REINFORCING CLIPPER LOW WILL PASS OVER THE REGION ON
TUESDAY. THE HIGH PRESSURE THAT FOLLOWS WILL SLIDE TO OUR SOUTHEAST
THURSDAY AND FRIDAY ALLOWING FOR WARM TEMPERATURES. ANOTHER COLD
FRONT IS EXPECTED AT THE END OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC HIPRES CENTERED OVER WVA ATTM. RESULTS SEEN ON SATPIX
/PRACTICALLY CLEAR SKIES THRUT/ AND IN WIND FIELDS /WHICH ARE BGNG
TO DIMINISH SWIFTLY/. AS THE RIDGE PASSES BY...WE SHUD HV A MOSUN
DAY WL RELATIVELY LGT WINDS AND WARMER TEMPS...COMPARED TO YDA. A
CPL OF SMALL TWEAKS MADE TO DATABASE...OTRW GOING FCST LOOKS GOOD.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
THE NEXT SHORTWAVE TROUGH IN THE NORTHERN STREAM QUICKLY APPROACHES
TONIGHT. SFC LOW AND BEST DYNAMIC LIFT WILL STAY WELL NORTH OF THE
AREA. HOWEVER A STRONG LLJ WILL ACCOMPANY THE TRAILING COLD FRONT
AND BRING DECENT MOISTURE RETURN IN THE NARROW WARM SECTOR WHICH
WILL SPREAD EASTWARD LATE TONIGHT (INCREASE IN PWAT FROM AROUND 0.10
AT 00Z LAST EVENING UP TO AROUND 0.75 LATE TONIGHT). GIVEN
CONSISTENCY OF QPF RESPONSE IN MODEL GUIDANCE...FORECAST POPS HAVE
BEEN INCREASED QUITE A BIT...WITH EVERYONE AT LEAST 20 PCT NOW. THE
ORIENTATION OF MOISTURE TRANSPORT WRT TO MOUNTAINS LENDS SLIGHTLY
HIGHER CHANCES EXIST FROM CENTRAL VA TO SOUTHERN MD...AND THE
GREATEST PROBS ARE IN THE WESTERN HIGHLANDS. MOST OF THE PRECIP WILL
FALL AFTER MIDNIGHT.

THE DIFFICULT PART OF THE FORECAST LIES IN P-TYPE (SHOULD ANY FALL).
WITH THE HIGH TO THE SE...SOUTHERLY FLOW WILL ALREADY BE
ESTABLISHED...SO TEMP FALLS WILL BE RELATED TO NOCTURNAL AND WETBULB
PROCESSES (AMBIENT AIRMASS QUITE DRY). LEANED TOWARD A BLEND OF 2M
TEMPS OVER MOS. IT IS ALSO POSSIBLE TEMPS LEVEL OFF OR PERHAPS EVEN
SLIGHTLY RISE IN SOME SPOTS. WITH THAT SAID...THERMAL PROFILES ARE
MARGINAL FOR RAIN AND SNOW WITH TEMPS GENERALLY IN THE 30S. NOT OUT
OF THE QUESTION THAT SOME SLEET COULD FALL OR EVEN A BRIEF PERIOD OF
FREEZING RAIN (MAINLY NORTHERN MD AND THE SOUTHERN HIGHLANDS).
HOWEVER WITHOUT A CLASSIC WARM NOSE...LIMITED TO ONLY RA/SN NOW. THE
AREAS OF MOST CONCERN FOR TEMPS ALSO HAVE LOWER CHANCE OF PRECIP.
THE HIGHEST ELEVATIONS OF THE POTOMAC HIGHLANDS COULD SEE AROUND AN
INCH OF SNOW...BUT MIXING IS EVEN POSSIBLE THERE.

THE FRONT AND ASSOCIATED PRECIP WILL QUICKLY SLIDE SE BY MID
MONDAY MORNING. CAA WILL BE LIMITED AS LLVL FLOW REMAINS WESTERLY.
EFFICIENT MIXING WILL MEAN POSSIBLE GUSTS TO AROUND 30 MPH.
HIGHEST TERRAIN COULD BE A LITTLE HIGHER...BUT APPEARS TO BE BELOW
ADVISORY CRITERIA. TEMPERATURES WILL ACTUALLY BE WARMER THAN THE
PREVIOUS DAY...WITH HIGHS RANGING FROM THE MID 50S TO MID 60S
EXCEPT IN THE HIGH TERRAIN (SIDED TOWARD WARMER GUIDANCE).

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
MONDAY NIGHT WILL BE THE SETTLED WEATHER BETWEEN SYSTEMS. NEXT UP IS
A FAST MOVING CLIPPER SHOWN IN THE GFS AND EURO FAIRLY SIMILARLY. IT
PASSES SE THROUGH THE MID ATL ON TUESDAY DAY. LOW LVL THICKNESSES ON
BOTH ALSO SHOW ANY PRECIP BEING RAIN. GFS IS MOST BULLISH ON POPS.
WENT BETWEEN THAT AND THE LESS GENEROUS EURO. ANY SHOWERS SHOULD BE
LIGHT.

AFTER THAT HIGH MOVES QUICKLY OVER AND THEN TO OUR EAST WITH SW FLOW
DEVELOPING. THAT SHOULD BRING A COUPLE OF WARM DAYS TO THE REGION
THU AND FRI BEFORE A COLD FRONT MOVES IN AT THE END OF THE WEEK.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH TODAY UNDER THE
INFLUENCE OF HIGH PRESSURE. NW WINDS WILL GRADUALLY BACK AND
BECOME SOUTHERLY BY LATE AFTERNOON. CLOUDS INCREASE TONIGHT AHEAD
OF AN APPROACHING COLD FRONT...BUT SHOULD REMAIN IN THE VFR
CATEGORY. THERE IS A CHANCE OF A PASSING SHOWER LATE TONIGHT/EARLY
MONDAY...GREATEST AT CHO. IF PRECIP IS DOES DEVELOP AT THE
NORTHERN TERMINALS...IT IS POSSIBLE IT COULD BE A RA/SN MIX.
WESTERLY WINDS INCREASE BEHIND THE FRONT AND GUST OF 20-30 KT
DURING THE DAY MONDAY.

MVFR POSSIBLE AT THE TERMINALS ON TUESDAY DAY WITH A CLIPPER PASSING
THROUGH. AFTER THAT...VFR EXPECTED THROUGH AT LEAST THU. MVFR TO
POSSIBLY IFR CONDITIONS MAY MOVE IN LATE IN THE WEEK IN ADVANCE OF
THE LATE WEEK COLD FRONT.

&&

.MARINE...
ALLOWED SCA FOR THE NRN BAY AND LOWER TIDAL PTMC TO EXPIRE AT
NOON...AND ADJUSTED MID BAY TO EXPIRE AN HR ERLR...AT 3PM. BASED
ON LTST TRENDS...IT SEEMS APPARENT EVEN THAT A TOUCH TOO GENEROUS
AND ANTICIPATE AN ERLR CANCELLATION.

HIGH PRESSURE SLIDES SOUTH THIS EVENING AND TURNS WINDS
SOUTHERLY. THESE WILL BEGIN TO CHANNEL UP THE BAY WITH ANOTHER SCA
GOING INTO EFFECT AT MIDNIGHT. A COLD FRONT WILL CROSS EARLY
MONDAY MORNING SHIFTING WINDS TO THE WEST AND PERHAPS BRINGING A
SHOWER. BEHIND THE FRONT...WESTERLY WINDS WILL GUST UP TO 30 KT
THROUGH MONDAY.

SMALL CRAFT ADVISORIES MAY NEED TO BE EXTENDED FROM MONDAY INTO
MONDAY NIGHT BEFORE WINDS CAN SUBSIDE. LATER TUE INTO TUE EVE IS
ALSO A POSSIBILITY AFTER THE CLIPPER PASSES THROUGH WITH AN INCREASE
IN WINDS TO NEAR 20KT POSSIBLE.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT MONDAY
     FOR ANZ530>534-537>543.
     SMALL CRAFT ADVISORY UNTIL 3 PM EDT THIS AFTERNOON FOR ANZ533-
     534-541-543.
     SMALL CRAFT ADVISORY FROM 9 AM TO 8 PM EDT MONDAY FOR ANZ535-
     536.

&&

$$

SYNOPSIS...CAS
NEAR TERM...HTS
SHORT TERM...ADS
LONG TERM...CAS
AVIATION...HTS/ADS/CAS
MARINE...HTS/ADS/CAS



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