Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 290057 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 857 PM EDT TUE APR 28 2015 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH WEDNESDAY. LOW PRESSURE WILL IMPACT THE REGION THURSDAY AND FRIDAY. HIGH PRESSURE WILL RETURN FOR THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/... GOING FCST IN GOOD SHAPE. MADE MINOR ADJUSTMENTS TO GRIDS...BUT WILL LEAVE ERLR DSCN INTACT AS IT ACCURATELY DESCRIBES FCST THOUGHT PROCESS. PREVIOUS DISCUSSION... REGION REMAINS ON EASTERN PERIPHERY OF HIGH PRESSURE CENTERED OVER THE CENTRAL PLAINS THROUGH TONIGHT. SCT CU THIS AFTN WILL SCATTER OUT TONIGHT...WITH MOSTLY CLEAR SKIES FOR MOST OF THE AREA. GUSTY NW WINDS THRU THE REMAINDER OF THE AFTN AS A RESULT OF MIXING WILL DIMINISH AFTER SUNSET WITH THE LOSS OF DAYTIME HEATING...BCMG LIGHT AND VRB WITH A WEAK PRESSURE GRADIENT OVER THE AREA. OVERNIGHT LOWS HOVERING RIGHT AROUND NORMAL..GENERALLY IN THE 40S. EXPECTING DRY CONDITIONS TO PERSIST THRU WED AS THE HIGH SLOWLY RETREATS AS LOW PRESSURE BUILDS IN FROM THE EAST AND SOUTH. LIGHT AND VRB FLOW IN THE MORNING WILL BRIEFLY BECOME NW BEFORE BACKING TO A SLY FLOW FOR THE AFTN AS A SFC TROUGH SETS UP. SCT CU WILL FORM YET AGAIN FROM DAYTIME HEATING...WITH INCREASING HIGH LVL CLOUDS FROM THE APPROACHING SYSTEM TO THE SOUTH. TEMPS SHOULD REACH THE 70S FOR MOST OF THE AREA...HOVERING RIGHT NEAR NORMAL. THOUGH DEPENDING ON THE EXACT TIMING OF THE WIND SHIFT COULD SEE TEMPS FLUCTUATE A COUPLE DEGREES. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... A WAVE OF LOW PRESSURE DEVELOPS OVER THE FORECAST AREA WEDNESDAY NIGHT...AND MODELS INDICATE IT WILL CLOSE OFF OVER THE APPALACHIANS BY THURSDAY MORNING. MEANWHILE...ANOTHER LOW PRESSURE GRADUALLY STRENGTHENS OFF THE SOUTHEAST US COAST. LIGHT WILL DEVELOP OVER THE REGION...ALTHOUGH NOT YET HIGHLY CONFIDENT ON EXACTLY WHERE IT WILL DEVELOP. LOWS GENERALLY IN THE UPPER 40S TO LOWER 50S...WITH MID 50S PSBL ALONG THE I-95 CORRIDOR. ON THURSDAY... THE WAVE OF LOW PRESSURE WILL PERSIST OVER MAINLY THE WESTERN PORTION OF THE FORECAST AREA...WHILE THE OFFSHORE LOW PRESSURE MOVES NORTHWARD TOWARDS THE WATERS EAST OF THE OUTER BANKS. RAIN WILL INCREASE IN COVERAGE...WITH LIKELY POPS OVER ALL OF THE FORECAST AREA BY AFTERNOON. AS A 500MB CLOSED LOW MOVES INTO THE OHIO VALLEY...COOLER AIR ALOFT WILL INCREASE LAPSE RATES ALONG AND WEST OF THE BLUE RIDGE. SB CAPE ON THE CHARLOTTESVILLE AIRPORT FORECAST SOUNDING REACHES AROUND 800 J/KG IN THE AFTN...SO INCLUDED SLIGHT CHANCE OF TSTMS. HIGHEST QPF FORECAST IS AROUND A HALF INCH OF RAIN THROUGH THURS AFTN OVER THE WESTERN HALF OF THE CWA. HIGHS IN THE 60S ACROSS THE CWA. ON THURSDAY NIGHT...LOW PRESSURE OVER THE OCEAN STRENGTHS AND ABSORBS THE INLAND LOW...AND THEN BEGINS TO MOVE OUT TO SEA. 500MB LOW WILL LIKELY PASS THROUGH WRN VA AND INTO NC. SHOWERS EXPECTED TO CONTINUE OVERNIGHT. 12Z GFS IS MORE AGGRESSIVE WITH PRECIP TOTALS OVER THE AREA THAN THE ECMWF. WILL TAKE THE MORE CONSERVATIVE QPF...WHICH SHOULD BE LESS THAN A QUARTER INCH. LOWS IN THE 40S MOST AREAS...WITH SOME LOWER 50S IN THE METRO AREAS. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS HAS BEEN THE CASE THE PAST FEW DAYS...SENSIBLE WX ON FRI WILL BE LARGELY DEPENDENT ON TRACK OF LOW PRESSURE SYSTEM. MOST RECENT MODEL GUIDANCE MORE CONSISTENT WITH PREVIOUS/RECENT RUNS OF ECMWF...WHICH INTENSIFIES/TRACKS THE LOW WELL OFFSHORE. HOWEVER...STILL POSSIBLE FOR LINGERING SHOWERS FRI FROM WRAPAROUND PRECIP...SO HELD ONTO CHC POPS FOR TO ACCOUNT FOR THIS. AMOUNTS SHOULD BE LIGHT...WITH DURATION/LOCATION OF SHOWER ACTIVITY LARGELY DEPENDENT ON HOW CLOSE THE LOW TRACKS TO OUR AREA. CLOUDINESS ON FRI WILL ALSO KEEP TEMPERATURES IN THE U50S/L60S. WARM-UP BEGINS IN EARNEST SAT AND CONTINUES THROUGH THIS FORECAST PERIOD...WITH HIGH TEMPS AOA 80 BY MON...WHICH IS NEARLY 10 DEGREES ABOVE CLIMO NORMS. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... VFR CONDITIONS THRU THE TAF PERIOD. WINDS WILL BECOME LIGHT AND VRB OVERNIGHT. LIGHT NW FLOW FIRST THING IN THE MORNING WILL BECOME LGT/VRBL FOR THE MIDDAY BEFORE ATTAINING SLY FLOW BY END OF THE DAY...DURING THE LATE PUSH. ALL WINDS EXPECTED TO REMAIN LESS THAN 10 KTS. PSBL SUB-VFR WITH POTENTIAL RAIN DVLPG WED NIGHT. LIGHT WINDS WITH A SOUTHERLY COMPONENT. RAIN LIKELY THURSDAY. GUIDANCE INDICATES MVFR CIGS LIKELY. WINDS E-SE AROUND 10KT OR LESS. POTENTIAL FOR IFR CONDS THU NIGHT WITH MOIST LOW LEVELS AND PSBL ADDITIONAL RAINFALL. WINDS E-NE 5-10KT. SUB-VFR CONDITIONS POSSIBLE FRI...BEFORE IMPROVING INTO WEEKEND AS IMPACT OF LOW PRESSURE MOVES AWAY. && .MARINE... WINDS HV SLOWLY RELAXED BELOW SMALL CRAFT CRITERIA. ALLOWED ADVY TO EXPIRE ON TIME. TREND FOR THE REST OF THE NGT WL BE FOR GRDLY DIMINISHING WINDS. SHUD HV NWLY FLOW THRU DAWN...ALBEIT AOB 10 KT. FLOW WL BECOME SLY BY TMRW AFTN...REMAINING BLO 10 KT. LOW PRESSURE WILL EMERGE INTO THE ATLANTIC OFF THE FL COAST WED NIGHT AND STRENGTHEN AS IT BEGINS TO MOVE TO THE NORTH. WINDS BECOME SW AROUND 10KT...WITH POTENTIAL FOR SOME GUSTS UP TO 15KT. WINDS MAY BE LIGHTER AND MORE ELY OVER THE NRN ZONES. LIGHT WINDS EXPECTED AGAIN THURSDAY...MAINLY E-SE WITH PERIODS OF RAIN OR SHOWERS. A SCA MAY BE NEEDED THURSDAY NIGHT AS THE COASTAL LOW REACHES THE WATERS EAST OF THE OUTER BANKS. POTENTIAL FOR SCA GUSTS FRI WILL BE DEPENDENT ON PROXIMITY OF LOW AS IT TRACKS TO OUR EAST/NORTHEAST. && .TIDES/COASTAL FLOODING... NWLY FLOW FOR THE PAST CPL DAYS HAVE LEFT WATER LVLS ON THE NORTHERN BAY AND UPR TIDAL POTOMAC ABT A HALF-FOOT BELOW ASTRO NORMS. HOWEVER...THE NEW TIDE IS ARRIVING AT SOLOMONS AND LEWISETTA VERY NEAR NORMAL. WITH LIGHT WINDS OVERNIGHT...EXPECT WATER LEVELS TO RETURN TO NORMAL BY DAWN WED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...SEARS/KCS NEAR TERM...SEARS/HTS SHORT TERM...KCS LONG TERM...MSE AVIATION...HTS/SEARS/KCS/MSE MARINE...HTS/KCS/MSE TIDES/COASTAL FLOODING...HTS

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