Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 291350 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 950 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/... 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 /14Z 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... OCCASIONAL NW WIND GUSTS TO 20 KT CONTINUE THIS MORNING. THESE SHOULD SUBSIDE GRADUALLY TODAY AS HIGH PRESSURE BUILDS IN. THE SCA WILL EXPIRE FROM NW TO SE. HV ALLOWED THE MID-UPR PTMC TO EXPIRE AT 9AM. IT MAY STILL BE CLOSE NEAR THE 301 BRIDGE...BUT TRENDS ARE DEFINITIVELY DOWN AS HIPRES BLDS. SCA FOR THE MID BAY REMAINS TIL 4PM...REST OF THE VALID WATERS EXPIRES AT NOON. 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 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 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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