Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190235 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1035 PM EDT MON AUG 18 2014 .SYNOPSIS... A WAVE OF LOW PRESSURE WILL MOVE OFF THE VIRGINIA COAST LATE TONIGHT. A FRONTAL BOUNDARY WILL REMAIN STALLED OVER THE SOUTHERN MID-ATLANTIC THROUGH THE END OF THE WEEK. && .NEAR TERM /THROUGH TUESDAY/... FRONTAL BOUNDARY IS STALLED OUT JUST SOUTH OF THE CWA. SOME CONVERGENCE NEAR AND TO THE NORTH OF IT HAS LED TO SHOWERS DEVELOPING OVER THE NORTHERN VIRGINIA PIEDMONT AND SOUTHERN MARYLAND. PW VALUES HAVE INCREASED AOA 1.6 INCHES AND THESE SHOWERS ARE EXHIBITING VERY LITTLE MOVEMENT...THEREFORE THEY WILL BE CAPABLE OF PRODUCING HEAVY RAINFALL AND PERHAPS SOME PONDING OF WATER. AM UNCERTAIN EXACTLY HOW FAR NORTH SHOWERS WILL BE ABLE TO EXPAND TO. MOST OF THE SHOWERS MAY WIND UP BEING SOUTH OF INTERSTATE 66...AND THIS IS WHERE THE HIGHEST POPS WILL RESIDE. MAY KEEP THE BALTIMORE AREA DRY FOR THE NIGHT GIVEN SOME OF THE LATEST GUIDANCE. THE STATIONARY FRONT WILL STAY NEAR THE HIGHLANDS AND SOUTH ACROSS SOUTHERN VA TUESDAY. AT THIS TIME IT IS HARD TO DEFINE BUT EASTERLY FLOW FROM THE JERSEY WILL SPREAD OUT ACROSS THE REGION LEADING TO FLOW UP AGAINST THE BOUNDARY. THIS SEEMS TO BE THE ONLY FORCING MECHANISM TUESDAY AND THEREFORE LOW CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY WEST OF THE BLUE RIDGE. SFC LOW PRESSURE FROM THE SHORTWAVE TROUGH TODAY WILL BE JUST OFF THE DELMARVA COAST TUESDAY. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/... ACTIVITY SHOULD BE DIURNAL IN NATURE AND WANE TUESDAY EVENING LEADING TO MOSTLY DRY CONDITIONS. EASTERLY FLOW WILL LEAD TO LOW CLOUDS AND PATCHY FOG FOR MUCH OF THE REGION TUESDAY NIGHT AND INTO WED MORNING. A TROUGH OF LOW PRESSURE WILL ENTER THE GREAT LAKES REGION WEDNESDAY AND SHOWERS AND THUNDERSTORMS WILL APPROACH THE HIGHLANDS WED MORNING AHEAD OF A COLD FRONT MOVING ACROSS THE OHIO VALLEY. LOW PRESSURE IS STILL PROGGED TO BE LOCATED OFF THE MID ATLANTIC COAST LEADING TO NE-E WINDS ACROSS MOST OF THE REGION. WINDS SHOULD BECOME SOUTHERLY BY WED AFTERNOON AND INSTABILITY WILL INCREASE. SHOWERS AND THUNDERSTORMS WILL MOVE EASTWARD THROUGHOUT WEDNESDAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... THE DOMINANT AXIS OF THE LARGE SCALE UPPER LEVEL TROUGH THAT WILL BE BRINGING THE MID-ATLANTIC ACTIVE WEATHER THIS WEEK WILL FINALLY DIG ACROSS THE EASTERN US THURSDAY AND FRIDAY. THIS WILL BRING A WEAK SURFACE COLD FRONT THROUGH THE AREA DURING THE DAY THURSDAY. SOUTHERLY FLOW AT THE SURFACE WILL ALLOW FOR ENOUGH PREFRONTAL WAA/MOISTURE ADVECTION THAT THURSDAY EVENING WILL SEE THE MOST INSTABILITY OF ANY DAY THIS WEEK...WITH POCKETS OF CAPE BETWEEN 1000 AND 1500 J. WITH JUST OVER 30 KTS OF SHEAR AND DRY LOW LEVELS/STEEP LOW LEVEL LAPSE RATES DAMAGING WINDS MAY BE A THREAT IN THUNDERSTORMS THAT DO INITIATE. COVERAGE OF STORMS WILL BE HIGHEST IN THE AFTERNOON WITH THE PEAK IN DIURNAL HEATING...THOUGH THE THREAT COULD CONTINUE THROUGH THE NIGHT DUE TO THE INCREASED UPPER LEVEL DYNAMICS IN THE AREA. AS THE UPPER LEVEL TROUGH AXIS MOVES OFF THE COAST A WAVE OF LOW PRESSURE WILL FORM OFF OF CAPE HATTERAS. ONSHORE FLOW AROUND THE NORTH SIDE OF THIS LOW WILL BRING A BACKDOOR COLD FRONT THROUGH THE AREA FRIDAY. THE SEASONABLY COOL AND MOIST AIRMASS BEHIND THIS FRONT WILL REMAIN OVER THE AREA THROUGH THE WEEKEND...BRINGING PERIODS OF LIGHT RAIN WITH A LOW CLOUD DECK. RAINFALL COULD BE ENHANCED ALONG THE BLUE RIDGE DUE TO UPSLOPING OF EASTERLY FLOW. HIGH PRESSURE WILL MOVE OVERHEAD LATE SUNDAY...ALLOWING SKIES TO BEGIN TO CLEAR AND BRINGING IN DRY CONDITIONS FOR THE BEGINNING OF THE WORKWEEK. TEMPS WILL BE IN THE LOW TO MID 80S ON THURSDAY THANKS TO PREFRONTAL WARM AIR ADVECTION. FRIDAY SATURDAY AND SUNDAY WILL ONLY SEE HIGHS INTO THE LOWER 70S AS A MARINE AIRMASS AND PLENTY OF SKY COVER WILL LIMIT DAYTIME HEATING. TEMPS WILL BEGIN TO CLIMB BACK TOWARD NORMAL TO BEGIN NEXT WEEK WITH HIGHS ON MONDAY MOSTLY IN THE LOWER 80S. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... SHOWERS HAVE DEVELOPED NOT TOO FAR SOUTH OF IAD/DCA THIS EVENING. AM UNCERTAIN HOW FAR NORTH THEY CAN REACH HOWEVER...SO HAVE LEFT SHRA OUT OF TAF ATTM. ATTENTION THEN TURNS TO POTENTIAL LOW CIG DEVELOPMENT OVERNIGHT. CHO SEEMS MOST LIKELY TO EXPERIENCE IFR. HAVE BACKED OFF ON IFR FURTHER NORTH PER LATEST GFS GUIDANCE WHICH IS SUPPORTED BY SREFS...BUT LATE NIGHT/EARY TUESDAY MVFR CIGS ARE POSSIBLE. ISO-SCT SHRA AND TSRA POSSIBLE AT MRB/CHO TUESDAY AFTERNOON. IFR CONDITIONS EXPECTED TUESDAY NIGHT/WEDNESDAY MORNING FOR LOW CIGS AND VSBYS. E-SE FLOW WILL CONTINUE WEDNESDAY AS A COLD FRONT APPROACHES FROM THE WEST. SHRA AND TSRA POSSIBLE WEDNESDAY. PERIODS OF SHOWERS AND THUNDERSTORMS MAY EFFECT AVIATION THURSDAY EVENING. LOW CEILINGS ARE EXPECTED AS A MARINE AIRMASS FILLS IN TO THE AREA LATE FRIDAY NIGHT THROUGH SUNDAY. && .MARINE... E/SE WINDS CONTINUE TONIGHT. LOCAL ENHANCEMENT MAY SUPPORT 15 KT WINDS UP THE LOWER TIDAL POTOMAC RIVER...BUT SPEEDS ARE EXPECTED TO REMAIN BELOW SCA THRESHOLDS. ONSHORE FLOW CONTINUES THROUGH MID-WEEK. CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY MARINE HAZARDS THROUGH THE LONG TERM. && .TIDES/COASTAL FLOODING...
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WENT AHEAD AND ISSUED COASTAL FLOOD ADVISORY FOR ANNE ARUNDEL COUNTY. ANOMALY UP NEAR 0.7 AT APAM2. PREV... ANOMALIES WERE RUNNING AROUND 1/2 FT ABOVE NORMAL ON THE WESTERN SHORE OF THE CHESAPEAKE BAY THIS EVENING. ANOMALIES ARE EXPECTED TO INCREASE A LITTLE OVERNIGHT. IT WON/T TAKE MUCH MORE TO SEND ANNAPOLIS INTO MINOR FLOOD...BUT IT IS UNCERTAIN IF THIS WILL OCCUR BY THE TIME OF HIGH TIDE. WILL CONTINUE TO MONITOR AS COASTAL FLOOD ADVISORY MAY BECOME NECESSARY...THIS IS LIKELY THE ONLY AREA THAT WILL BE VULNERABLE FOR TONIGHT/S HIGH TIDE.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...COASTAL FLOOD ADVISORY UNTIL 4 AM EDT TUESDAY FOR MDZ014. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...BJL NEAR TERM...BPP/HAS SHORT TERM...HAS LONG TERM...CEB AVIATION...BPP/HAS/CEB MARINE...BPP/HAS/CEB TIDES/COASTAL FLOODING...BPP

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