Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 301243 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 843 AM EDT MON MAR 30 2015 .SYNOPSIS... A COLD FRONT WILL CROSS THROUGH THE REGION 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/...
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UPDATE TO ADD SMALL CRAFT ADVISORY FOR TUE AFTN AND SOME MODIFICATIONS TO THE CURRENT/NEAR TERM CONDS. DECREASED POPS FOR THE I-95 CORRIDOR AND UPSLOPE AREAS OF THE MTNS. ADJUSTED TEMPS/SKY FOR THE UPPER WAVE PASSAGE AND QUICKLY CHANGING CONDS. FROM PREV DISC... A COLD FRONT WILL MOVE ACROSS THE CWA LATE THIS MORNING THROUGH EARLY AFTERNOON. SOUTHERLY FLOW AND A HIGH SUN ANGLE WILL SUPPORT LIQUID RAIN FOR ANY AREAS THAT RECEIVE PRECIPITATION EAST OF THE MOUNTAINS. WINDS WILL SHIFT TO THE WNW...WITH ENOUGH DOWNSLOPE COMPONENT TO SUPPORT HIGH TEMPS REACHING THE UPPER 50S AND LOWER 60S OVER MOST OF THE FORECAST AREA. HIGH TEMPS BASED ON WARMER MAV GUIDANCE. STEEP LAPSE RATES IN THE LOWEST 10KFT WILL SUPPORT GUSTY WINDS...MAINLY 20-25KTS. SOME GUSTS UP TO 30KTS POSSIBLE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... HIGH PRESSURE BUILDS IN BRIEFLY MONDAY NIGHT...WITH NO PRECIPITATION EXPECTED. WINDS WILL DIMINISH AND SHIFT TO THE SW. LOW TEMPS MAINLY IN THE UPPER 30S AND LOW 40S...WITH SOME COOLER SPOTS NEAR THE MASON DIXON LINE...ALONG THE RIDGE TOPS AND IN SHELTERED VALLEYS. CLIPPER LOW DIVES ACROSS THE REGION TUESDAY. STILL SOME MODEL UNCERTAINTY OVER HOW FAR SOUTH THE LOW DROPS AS IT CROSSES THE REGION...WITH 00Z GFS AND NAM KEEPING IT CLOSER TO THE MASON DIXON LINE AND THE ECMWF BRINGING IT FURTHER SOUTH ACROSS VA. EARLY MORNING TEMPS SUPPORT POTENTIAL FOR A RAIN/SNOW MIX OVER THE HIGHLANDS. FOR THE REST OF THE AREA...ANY PRECIP SHOULD BE WELL ENOUGH INTO THE MORNING AND AFTERNOON THAT PRECIP WOULD BE RAIN. HIGHS BASED ON WARMER MAV GUIDANCE...MAINLY IN THE 60S WITH SOME PORTIONS OF THE CENTRAL FOOTHILLS AND PIEDMONT REACHING 70. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A FEW POPS LINGER TUESDAY EVENING ON WRAP AROUND OF REINFORCING CLIPPER. COLD FRONT SURGES THROUGH AREA...WITH PLENTY OF DRY AIR TO END POPS BY MIDNIGHT. SURGE OF NWLY/NLY AIR WITH CLIPPER COLD FRONT WITH OVERNIGHT 30 TO POSSIBLY 40 MPH WIND GUSTS. HIGH PRESSURE MOVE SE ACROSS SWRN LWX ZONES WEDNESDAY WITH DRY PERIOD AND NEAR TO BELOW NORMAL TEMPERATURES INTO THURSDAY. NLY FLOW FROM WED BECOMES RETURN FLOW WEDNESDAY NIGHT ON BACKSIDE OF HIGH. WARMING TREND THEN THURSDAY AND FRIDAY. WITH DRY AND SUNNY CONDITIONS...THURSDAY MAY BE WARMEST DAY OF THE WEEK. HOWEVER...GUIDANCE STILL HAS FRIDAY WARMER DESPITE A FRONT CROSSING DURING PEAK HEATING. POSSIBLE EXTENDED RAIN EVENT AS A WARM FRONT SETS UP OVER THE AREA FRIDAY AND A COLD FRONT CROSSING FRIDAY NIGHT. BERMUDA HIGH OPENS GULF WITH PLENTY OF MOISTURE. LATER SHIFTS WILL NEED TO MONITOR FOR HEAVY RAIN/FLOODING POTENTIAL. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... PRIMARILY VFR. PERIODIC LIGHT PRECIPITATION POSSIBLE IN THE EARLY MORNING HOURS. ANY PRECIPITATION BEFORE SUNRISE MAY BE A MIX OF RAIN...SLEET AND SNOW AT THE BALTIMORE/WASHINGTON TERMINALS AND KMRB...BUT NO ACCUMULATION IS EXPECTED. WINDS START FROM THE S-SW...BUT WILL SHIFT TO W-NW DURING THE DAY AND BECOME GUSTY. GUSTS MAINLY AROUND 20KT...BUT MAY PEAK NEAR 30KTS AT TIMES. WINDS WILL DIMINISH MONDAY NIGHT. YET ANOTHER QUICK-MOVING UPPER LEVEL LOW WILL SWING BY THE AREA ON TUE...MAINLY DURING THE DAYTIME HRS. ANY PCPN IS EXPECTED TO BE RAIN...W/ WARMER TEMPS WORKING INTO THE SRN END OF THE SYSTEM AS IT PASSES BY. BRIEF MVFR CIGS COULD RESULT FROM THIS SYSTEM DURING THE DAYTIME HRS. COLD FRONT CROSSES TUESDAY EVENING WITH RAIN QUICKLY ENDING BY SUNSET AND NWLY FLOW SURGING TO 30 KT OR SO THROUGH THE NIGHT. HIGH PRESSURE CROSSES WEDNESDAY WITH RETURN FLOW THEN WEDNESDAY NIGHT INTO FRIDAY AHEAD OF THE NEXT COLD FRONT THAT CROSSES FRIDAY NIGHT. && .MARINE... SCA IN EFFECT ACROSS CHESAPEAKE BAY AND THE LOWER TIDAL POTOMAC RIVER BEFORE 8 AM...THEN EXPANDING TO INCLUDE ALL WATERS THROUGH EARLY MONDAY EVENING. WINDS BEGIN FROM THE S-SW...BUT WILL SHIFT TO THE W-NW BY EARLY AFTERNOON. HIGHEST GUSTS SHOULD BE AROUND 25-30 KTS. CANNOT RULE OUT GALES ENTIRELY...BUT IT WOULD REQUIRE MIXING TO THE TOP OF THE BOUNDARY LAYER AND IS NOT SUPPORTED BY A MODEL CONSENSUS. WINDS DIMINISH MONDAY NIGHT WITH HIGH PRESSURE BRIEFLY BUILDING IN. A SCA MAY BE NEEDED AGAIN TUESDAY AS ANOTHER COLD FRONT CROSSES THE REGION. SCA EXPECTED ALL WATERS TUESDAY NIGHT AS COLD FRONT CROSSES THE AREA. HIGH PRESSURE SHIFTS SE OVER INTERIOR MID-ATLANTIC WEDNESDAY...SCA LIKELY THROUGH MIDDAY BEFORE CALMING. RETURN FLOW THEN DEVELOPS WEDNESDAY AND PERSISTS THROUGH FRIDAY AHEAD OF THE NEXT COLD FRONT CROSSING FRIDAY NIGHT. . && .TIDES/COASTAL FLOODING... WATER LEVELS ARE RUNNING AROUND A HALF FOOT ABOVE ASTRONOMICAL PREDICTIONS DUE TO THE RETURN OF SOUTHERLY WINDS. TIDES ARE EXPECTED TO DROP BELOW ASTRONOMICAL PREDICTIONS MONDAY AFTERNOON UNDER W-NW WINDS BEHIND A COLD FRONT. THERE IS POTENTIAL FOR BLOWOUT TIDES. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530>534-537>543. SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EDT TUESDAY FOR ANZ530>543. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ535- 536.
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&& $$ UPDATE...GMS PREV DISCUSSION...KCS/BAJ

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