Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 060104 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 904 PM EDT SUN JUL 5 2015 .SYNOPSIS...
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A STATIONARY FRONT WILL REMAIN TO THE SOUTH THROUGH TONIGHT BEFORE LIFTING NORTH AS A WARM FRONT MONDAY. A WEAK COLD FRONT WILL APPROACH THE REGION WEDNESDAY...THEN LINGER OVER OUR AREA THROUGH THE EXTENDED.
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&& .NEAR TERM /THROUGH MONDAY NIGHT/...
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AN UPPER LEVEL LOW IS LOCATED OVER KY WITH AN EMBEDDED SHORTWAVE TROUGH ENTERING WV. A STATIONARY FRONT IS DRAPED ACROSS THE NC/VA BORDER THIS EVENING. SHOWERS AND THUNDERSTORMS HAVE BEEN ONGOING ACROSS SOUTHERN VA THIS AFTERNOON AND EARLY EVENING IN VICINITY OF THE FRONT AND UPPER LOW. THE STEERING FLOW IS WEAK AND ORIENTED S-SWTO N-NE AND ACTIVITY IS SLOW MOVING. THE MID- ATLANTIC IS STARTING TO SEE ACTIVITY MOVE INTO THE CENTRAL FOOTHILLS AND PIEDMONT THIS EVENING. VERY HEAVY RAIN IS EXPECTED OVERNIGHT AS PWATS RANGE FROM 1.5-2.0 ACROSS VA. EXPECT THIS TREND TO CONTINUE AS THE SHORTWAVE TROUGH APPORACHES TONIGHT. HEAVY SHOWERS WITH ISOLATED THUNDERSTORMS WILL SPREAD THE REGION BY MONDAY MORNING. AT THIS TIME...FLASH FLOOD WATCH CONTINUES ACROSS HIGHLAND AND PENDLETON COUNTIES WHERE FFG IS LOW. FURTHER EAST AND NEAR THE CENTRAL FOOTHILLS...LOCALIZED FLOODING IS POSSIBLE AS MULTIPLE ROUNDS OF SHOWERS BEGIN TO MOVE INTO THE AREA. COVERAGE WILL BE WEAK AND THEREFORE NO FF WATCH EXTENSION WAS DONE. AROUND 1 INCH IS EXPECTED IN HEAVY SHOWERS WITH THE POTENTIAL OF 2 INCHES IN AREAS THAT SEE TRAINING THIS EVENING. PREVIOUS DISCUSSION... THE STATIONARY FRONT WILL EVENTUALLY BEGIN TO LIFT NORTH AS A WARM FRONT TONIGHT...EVENTUALLY PUSHING NORTH OF THE AREA BY MONDAY NIGHT. THINKING THE FRONT WILL PROVIDE THE NEEDED FORCING TO TRIGGER SHOWERS EAST OF THE BLUE RIDGE AS THE SHORTWAVE ENERGY LOOKS TO STAY MORE TO THE WEST. AS SUCH...HAVE HIGHER POPS WEST FIRST HALF OF THE NIGHT...THEN PUSHING EAST SECOND HALF OF THE NIGHT. SOME QUESTION AS TO HOW LONG THE PCPN LINGERS IN THE MORNING...THOUGH GENERAL IDEA WOULD BE SOME CLEARING MON MORNING BEFORE THE NEXT ROUND OF CONVECTION THEN MON AFTN AS THE WARM FRONT LIFTS THROUGH AND THE NEXT SHORTWAVE MOVES THROUGH. THIS SHORTWAVE LOOKS TO BE FURTHER EAST...SO THE THREAT OF OF TSTMS ENCOMPASSES THE ENTIRE AREA MON AFTN/EVENING. SVR THREAT LOOKS TO BE MORE MARGINAL AS INSTABILITY IS CURRENTLY LIMITED. HOWEVER...IF WE CAN SCATTER OUT MORE IN THE MORNING...COULD SEE BETTER INSTABILITY. SHEAR IS STRONGER ON MONDAY...THOUGH STILL NOT COMPLETELY SELLING ON SVR. BACKING WINDS WITH THE WARM FRONT COULD HINT AT PSBL TOR THREAT...BUT STILL ON THE LOW END. WILL HIGHLIGHT THAT HEAVY RAIN WILL BE A THREAT AGAIN MON AFTN AS PWATS STAY WELL ABV NORMAL...ESP OVER EASTERN AREAS. PCPN WILL SLOWLY TAPER OFF MON NIGHT AS THE FRONT CLEARS TO THE NORTH.
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... MID/UPPER LEVEL LOW STARTS PULLING AWAY FROM OUR AREA TUESDAY MORNING...AS IT IS SHEARED APART...AND IS INGESTED INTO MAIN BELT OF WESTERLIES ASSOCIATED WITH THE NORTHERN STREAM. MOST OF TUE APPEARS TO BE RELATIVELY DRY UNDER SUBSIDENCE FROM DEPARTING LOW AND LITTLE IN THE WAY OF LIFTING MECHANISMS IN THE AREA. ALTHOUGH...CANNOT ENTIRELY RULE OUT AN ISOLATED AFTN TSTM WITH SFC HEATING COMBINED WITH MESOSCALE FEATURES (SUBTLE BOUNDARIES...TERRAIN)...THOUGH ATTM CHCS APPEAR VERY LOW. GUIDANCE HAS BEEN TRENDING HIGHER WITH TEMPS...LIKELY DUE TO MORE INSOLATION...SO NUDGED THEM UP A BIT WITH TEMPS IN THE U80S ACROSS THE REGION. LIGHT SWLY WINDS USHER IN SOME DRIER AIR...WHICH KEEP HEAT INDICES IN L90S. WEAK COLD FRONT APPROACHES THE REGION WED. INCREASED POPS SOMEWHAT IN THE AFTN...AS QPF SIGNAL IS BECOMING MORE CONSISTENT. DEEP LAYER FLOW REMAINS RATHER WEAK THROUGH THE PERIOD AND INSTABILITY IS ALSO RATHER LIMITED...SO EXPECTING MOST ACTIVITY TO BE UNORGANIZED. TEMPS INCREASE SLIGHTLY UNDER CONTINUED AIRMASS MODIFICATION...BUT SHOULD ONLY BE A FEW DEGREES ABOVE CLIMO NORMS. && .LONG TERM /THURSDAY THROUGH SUNDAY/...
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COLD FRONT MOVES OVER THE CWA WED NIGHT AND LINGERS THROUGH THE WEEKEND. INSTABILITY FROM THIS SYSTEM WILL ALLOW FOR THE RISK OF ISOLATED/SCATTERED SHOWERS AND/OR TSTMS EACH DAY. TEMPS WILL BE NEAR NORMAL FOR THIS TIME OF THE YEAR.
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&& .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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VFR/MVFR CONDITIONS EXPECTED THIS EVENING BEFORE BECOMING MVFR/IFR BY MONDAY MORNING. SHRA WILL MOVE INTO THE TERMINALS FROM S TO N IMPACTING CHO ALREADY. VSBYS MAY DROP TO IFR/SUB-IFR IN SHRA/TSRA BUT MAIN IMPACT WILL BE LOW CIGS INTO MONDAY MORNING. ISOLATED TS EXPECTED TONIGHT AND CONFIDENCE IS LOW TO PUT IN TAFS. VFR CONDITIONS RETURN MON MORNING AS THE PCPN TAPERS OFF. ANOTHER ROUND OF SHOWERS AND TSTMS LIKELY MON AFTN WHICH ONCE AGAIN WILL RESULT IN SUB-VFR CONDITIONS. WINDS GENERALLY 10 KTS OR LESS FROM THE SE THRU MON. ANY TSTM COULD PRODUCE SPORADIC GUSTS UP TO 40 KTS. EXPECT VFR CONDS TUE...AS MID/UPPER LOW DEPARTS OUR AREA AND WE ARE IN REGION OF SUBSIDENCE. ATTM VERY LOW CHC FOR AFTN TSTM TUE WITH LOCALIZED SUB-VFR CONDS IF THEY OCCUR. BETTER CHCS FOR SHWRS/TSTMS...AND LOCALIZED SUB-VFR CONDS ON WED AS COLD FRONT APPROACHES THE REGION. VFR CONDITIONS EXPECTED FOR WED NIGHT AND THURS. SUB-VFR CONDITIONS PSBL DUE TO SHOWERS AND/OR TSTMS.
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&& .MARINE... SUB-SCA CONDITIONS ON ALL WATERS THRU MON MORNING. HAVE ISSUED A SCA FOR THE LOWER TIDAL POTOMAC AND CHESAPEAKE BAY MON AFTN AND EVENING FOR INCRG SLY FLOW RESULTING IN GUSTS UP TO 20 KTS. SUB- SCA CONDITIONS RETURN FOR ALL WATERS MON NIGHT. WINDS EXPECTED TO SUBSIDE TUE MORNING AS PRESSURE GRADIENT RELAXES AND REGION IS UNDER SUBSIDENCE FROM DEPARTING LOW. WINDS EXPECTED TO REMAIN BELOW SCA CRITERIA THROUGH WED...THOUGH MARINERS SHOULD WATCH OUT FOR TSTM CHCS WED AFTN. SUB-SCA CONDITIONS EXPECTED FOR WED NIGHT AND THURS. PSBL SHOWERS AND TSTMS ACROSS THE WATERS DURING THIS PERIOD. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...FLASH FLOOD WATCH UNTIL 6 AM EDT MONDAY FOR VAZ503-504. WV...FLASH FLOOD WATCH UNTIL 6 AM EDT MONDAY FOR WVZ505-506. MARINE...SMALL CRAFT ADVISORY FROM 2 PM MONDAY TO 2 AM EDT TUESDAY FOR ANZ534-537-543.
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&& $$ SYNOPSIS...SEARS/MSE NEAR TERM...SEARS/HAS SHORT TERM...MSE LONG TERM...IMR AVIATION...SEARS/HAS/IMR/MSE MARINE...SEARS/HAS/IMR/MSE

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