Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 290757
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
357 AM 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/...

MORNING ANALYSIS SHOWS DEEP UPPER LEVEL TROUGH ALONG THE EASTERN
SEABOARD WITH A SHORTWAVE RIDGE OVER THE GREAT LAKES/MS VALLEY. SFC
HIGH PRESSURE IS CENTERED OVER THE OHIO VALLEY. IT WILL BE A CLEAR
AND COLD START TO THE DAY...WITH ALL LOCATIONS BELOW THE 30F MARK.
THE HIGH WILL QUICKLY SLIDE TO THE CAROLINA COAST TODAY. DESPITE
LESSENING WINDS AND FULL SUN FOR MUCH OF THE DAY...TEMPERATURES WILL
REMAIN BELOW NORMAL AS THERE WILL NOT BE RAPID WAA. DID SIDE WITH
WARMER GFS-BASED GUIDANCE FOR HIGHS RANGING FROM THE MID 40S TO
LOWER 50S.

&&

.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 /08Z SUNDAY THROUGH THURSDAY/...

VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH TODAY UNDER THE
INFLUENCE OF HIGH PRESSURE. THE THREAT FOR GUSTS TO 20 KT WILL
DIMINISH THIS MORNING. THE 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...

OCCASIONAL NW WIND GUSTS TO 20 KT CONTINUE EARLY THIS MORNING. THESE
SHOULD SUBSIDE GRADUALLY TODAY AS HIGH PRESSURE BUILDS IN. THE SCA
WILL EXPIRE FROM NW TO SE. 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.

&&

.CLIMATE...

EARLY THIS MORNING...LOW TEMPERATURES WILL APPROACH RECORD LOWS FOR
THE MARCH 29TH AT DULLES.  BWI AND DCA RECORDS SHOULD REMAIN SAFE.

SITE...3/29 RECORD MIN T
DCA......18 (1923)
BWI......18 (1923)
IAD......20 (1982)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ530>532-
     537>540-542.
     SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EDT MONDAY
     FOR ANZ530>534-537>543.
     SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ533-
     534-541-543.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR
     ANZ535-536.
     SMALL CRAFT ADVISORY FROM 9 AM TO 8 PM EDT MONDAY FOR ANZ535-
     536.

&&

$$
SYNOPSIS...CAS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...CAS
AVIATION...ADS/CAS
MARINE...ADS/CAS
CLIMATE...CAS/DFH


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