Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 021440 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1040 AM EDT THU JUL 2 2015 .SYNOPSIS... A STATIONARY FRONT WILL REMAIN OVER CENTRAL VIRGINIA AND SOUTHERN MARYLAND THROUGH TODAY...AND LINGER OVER THE AREA THROUGH THE WEEKEND. WITH SEVERAL WAVES OF LOW PRESSURE WILL MOVE EAST ALONG THE FRONT AS AN ACTIVE PATTERN CONTINUES. HIGH PRESSURE WILL RETURN FOR THE FIRST HALF OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... NEARLY STATIONARY FRONT IS STRETCHED EAST-TO-WEST ACROSS CENTRAL VA THIS MORNING WITH A WEAK WAVE OF LOW PRESSURE OVER THE CHESAPEAKE BAY. SHOWERS ARE BECOMING MORE SCATTERED IN NATURE LATE THIS MORNING...BUT ARE EXPECTED TO BECOME MORE NUMEROUS THIS AFTERNOON AHEAD OF VORT MAX APPROACHING FROM OHIO VALLEY. THIS WILL BE TARGETED TO SOUTHERN AREAS. CLOUD COVER IS FAIRLY EXTENSIVE AND SHOULD LIMIT INSTBY...BUT BREAKS SEEN IN VISIBLE IMAGERY MAY ALLOW POCKETS OF SLIGHTLY HIGHER INSTBY. WITH MOST OF CWA ON NORTH SIDE OF BOUNDARY...WOULD NOT EXPECT A WIDESPREAD STRONG THUNDERSTORM THREAT. HOWEVER WITH DEEP LAYER SHEAR AROUND 30 KT...THERE IS A CHANCE OF A FEW STRONGER STORMS GIVEN SUFFICIENT INSTBY...MAINLY IN SOUTHERN AREAS. GIVEN WET SOILS ACROSS THE AREA...WILL ALSO HAVE TO WATCH FOR REPETITIVE STORMS WHICH COULD PRODUCE LOCALIZED FLOODING ISSUES WITH PWATS AOA 1.5 INCHES. MAIN CHANGES WITH MORNING UPDATE INVOLVED ADJUSTING POPS BASED ON LATEST GUIDANCE. ALSO BLENDED IN LATEST LAMP TEMPERATURES...WHICH LOWERED MAX TEMPS A DEGREE OR TWO WITH THE CLOUDS. PRECIP COVERAGE IN GREATER QUESTION TONIGHT...AS THERE MAY BE A LULL AFTER DEPARTING WAVE...ESPECIALLY DEPENDING ON HOW FAR SOUTH THE FRONT SINKS. LOWS TONIGHT WILL GENERALLY BE SIMILAR TO THIS MORNING`S. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... RIGHT NOW...THE BEST CHANCE OF PRECIPITATION ACROSS THE AREA WOULD APPEAR TO BE FRIDAY...AS A DECENT SHORTWAVE AND VORT MAX MOVES ACROSS THE AREA SUPPORTING A MORE NOTABLE LOW PRESSURE WAVE AT THE SURFACE ALONG THE STALLED FRONT. UNCERTAINTY REMAINS AS TO HOW LONG IT LINGERS FRIDAY NIGHT...WITH SOME GUIDANCE ALLOWING IT TO PULL AWAY FAST ENOUGH SO THAT THE REGION DRIES OUT...WHILE OTHER MODELS KEEP THE SHOWERS OVER THE AREA. FOR NOW KEPT HIGHEST POPS DURING THE DAY...BUT THE POSSIBILITY OF DECENT PRECIPITATION DURING FRIDAY NIGHT IS DEFINITELY OF NOTE AND IF THERE IS BETTER CONSENSUS IN THE FUTURE...POPS MAY CERTAINLY END UP SIGNIFICANTLY HIGHER. TEMPERATURES WILL BE COOL FRIDAY WITH MANY AREAS FAILING TO REACH 80...WHILE LOWS WILL REMAIN SIMILAR TO RECENT DAYS. FOURTH OF JULY...STATIONARY FRONT LINGERING OVER THE AREA (WITH SHORTWAVES RIDING ALONG IT) MAKES FOR A COMPLICATED FORECAST. CONSENSUS AMONG 00Z GFS/ECMWF/NAM IS FOR A MORNING LOW TO CROSS SRN MD/WATERS WITH A SECONDARY SHORTWAVE TO CROSS THE POTOMAC HIGHLANDS LATE IN THE AFTERNOON. BOTH OF THESE FEATURES WILL SHIFT THE FRONTAL SYSTEM...TO AN UNCERTAIN EXTENT. FELT THE LIKELY POPS FOR THE SRN HALF OF THE CWA WAS A BIT HIGH...SO WENT CHANCE MOST PLACES IN THE AFTERNOON. WITH SHORTWAVE ENTERING THE WEST IN THE PEAK HEATING...WENT LIKELIES FOR THE POTOMAC/ALLEGHENY HIGHLANDS. MAX TEMPS LIMITED BY STRATO-CU AND ANY PRECIP...GENERALLY LOW 80S (WITH DEWPOINTS IN THE MID 60S...EXPECT A BIT OF A HEAT INDEX TO THE MID 80S). SATURDAY NIGHT...KEY FOR EVENING POP IS PROGRESSION OF WEAK SHORT WAVE FROM THE CENTRAL APPALACHIANS AND REMAINING INSTABILITY. THOSE DETAILS WILL BECOME MORE APPARENT WITH FUTURE MODEL RUNS...BUT CURRENT BEST GUESS IS TO HAVE SCATTERED THUNDERSTORM ACTIVITY CONTINUE. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... FRONTAL BOUNDARY SOUTH OF THE AREA DRIFTS FARTHER SOUTH SUNDAY AND MONDAY AS UPR RIDGE BUILDS EAST OVER THE MIDWEST. ANY ISOLATED TO POSSIBLY SCATTERED THUNDERSTORMS BOTH DAY LOOK TO BE DIURNALLY DRIVEN. QUIET WX TUES UNDER HIGH PRESSURE AND NEAR NORMAL TEMPS. NEXT COLD FRONT APPROACHES REGION FROM THE MIDWEST WEDNESDAY AND SLOWS WITH MORE ACTIVE WEATHER INTO LATE NEXT WEEK. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... FAIRLY LIGHT WINDS FROM THE NORTH THIS MORNING SHIFTING EASTERLY BY TONIGHT. VFR CIGS AND VIS OUTSIDE OF ANY SHOWERS. THE SHOWERS HAVE BEEN DECREASING IN COVERAGE AND SHOULD SEE THE THREAT FOR LOWER VSBYS DECREASE THROUGH THE MIDDAY HOURS. THERE WILL BE A RENEWED CHANCE FOR SHOWERS AND STORMS LATER THIS AFTERNOON...ESPECIALLY AT CHO. EVEN OUTSIDE OF SHOWERS...SOME HAZE MAY LINGER WITH VSBYS 5-9 SM. FORECAST A BIT MORE UNCERTAIN OVERNIGHT IN REGARDS TO SHOWERS AND POTENTIAL IMPACTS TO AVIATION. LOW PRESSURE MAY BRING SOME STEADIER RAIN TO THE REGION BY FRIDAY POSSIBLY INTO FRIDAY NIGHT...WITH POTENTIAL FOR A MORE SUSTAINED PERIOD OF MVFR OR EVEN IFR CIGS/VIS. TIMING AND NORTHWARD EXTENT OF THIS IS STILL IN QUESTION AND SO CONFIDENCE IS NOT HIGH. STATIONARY FRONT LINGERS JUST SOUTH OF DC METROS SATURDAY...BEFORE DRIFTING FARTHER SOUTH SUNDAY AND MONDAY. SCATTERED THUNDERSTORMS THROUGH SATURDAY INTO THE EVENING ACROSS THE TERMINALS. MORNING NELY FLOW 10 TO 15 KT AS LOW PASSES SRN MD. DIURNALLY ISOLATED SUN/MON. QUIET WX TUES. && .MARINE... WINDS SHOULD STAY BELOW SCA LEVELS TODAY...WITH NORTHERLY WINDS BELOW 10 KNOTS GRADUALLY SHIFTING TO EASTERLY. A FEW HEAVIER SHOWERS OR EVEN AN ISOLATED THUNDERSTORM ARE POSSIBLE TODAY...WHICH COULD PRODUCE GUSTIER WINDS. THE GREATEST CHANCE FOR STRONGER STORMS WILL BE OVER THE LOWER TIDAL POTOMAC AND LOWER MD CHESAPEAKE BAY. WINDS MIGHT INCREASE TO SCA LEVELS LATER FRIDAY AND FRIDAY NIGHT AS A LOW PRESSURE WAVE PASSES BY TO THE SOUTH AND SOUTHEAST WITH MORE WIDESPREAD RAIN SHOWERS. CONFIDENCE IS NOT HIGH SO DID NOT ISSUE AN SCA JUST YET...BUT IT MAY BE NEEDED. WILL NEED TO WATCH A WEAK LOW PASS SRN MD SATURDAY MORNING FOR NELY GUSTS AROUND 20 KT. SCATTERED THUNDERSTORMS POSSIBLE ALL DAY/EVENING. LIGHT ONSHORE FLOW THEN SUNDAY AND MONDAY AS FRONT DIPS FARTHER SOUTH OF THE AREA. QUIET TUESDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BAJ NEAR TERM...ADS/RCM SHORT TERM...BAJ/RCM LONG TERM...BAJ AVIATION...BAJ/ADS/RCM MARINE...BAJ/ADS/RCM

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