Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 191403 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1003 AM EDT TUE AUG 19 2014 .SYNOPSIS... LOW PRESSURE WILL MOVE AWAY FROM THE AREA TODAY...BUT A BOUNDARY WILL REMAIN STATIONARY OVER THE REGION. THE BOUNDARY WILL REMAIN OVERHEAD THROUGH THURSDAY BEFORE SLOWLY DROPPING SOUTH AS A COLD FRONT FRIDAY INTO THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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LOW PRESSURE IS SLOWLY MOVING TO THE SOUTHEAST AND OFF THE VA TIDE WATER COAST THIS MORNING. A STATIONARY FRONT STAYS LOCATED ACROSS THE MID ATLANTIC FROM THE PANHANDLE OF WV TO CENTRAL VA THIS MORNING. NE-E WINDS CONTINUE TO MOVE INTO THE REGION ON THE DRIER SIDE OF THE BOUNDARY. DRIER AIR WILL MOVE INTO THE REGION FROM THE NE AND MOSTLY SUNNY CONDITIONS ARE EXPECTED FOR NE MD. CLOUDS INCREASE FURTHER SOUTH AS EASTERLY FLOW PUSHES AGAINST THE BLUE RIDGE MTNS AND INTERACTS WITH THE STATIONARY BOUNDARY THAT IS IN PLACE. DEWPTS IN THE UPPER 60S TO LOW 70S ARE LOCATED ON THE WETTER SIDE OF THE BOUNDARY AND NEAR THE SFC LOW. ISO-SCT SHOWERS WILL BE POSSIBLE ACROSS SOUTHERN MD THIS MORNING AND INTO THE AFTERNOON AS THE SFC LOW TRACKS EASTWARD. AS TEMPS RISE NEAR 80...MOISTURE WILL ALLOW SHOWERS AND ISO THUNDERSTORMS TO FORM NEAR THE STATIONARY FRONT WHICH WILL BE LOCATED NEAR THE POTOMAC HIGHLANDS/ALLEGHENY FRONT. LITTLE FORCING ALOFT WILL LIMIT WIDESPREAD AND STRONG STORMS. SHOWERS THAT DO FORM WILL MOVE SLOWLY SINCE 12Z IAD RAOB HAS A ZERO SPEED STORM MOTION. SOME PLACES MAY SEE ISOLATED AMTS OF HEAVY RAIN. PREVIOUS DISCUSSION... ANY CONVECTION WILL DISSIPATE ACROSS MOST LOCATIONS THIS EVENING. THERE MAY BE A FEW SHOWERS THAT HANG AROUND OVERNIGHT ACROSS THE POTOMAC HIGHLANDS...BUT EVEN ACROSS THESE AREAS MOST OF THE TIME WILL BE DRY. PATCHY LOW CLOUDS AND FOG ARE EXPECTED...ESPECIALLY ACROSS THE POTOMAC HIGHLANDS INTO CENTRAL VIRGINIA WHERE THERE WILL BE A LITTLE MORE MOISTURE. MIN TEMPS WILL RANGE FROM THE UPPER 50S AND LOWER 60S IN THE POTOMAC HIGHLANDS TO NEAR 70 IN DOWNTOWN WASHINGTON AND BALTIMORE.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... A STATIONARY BOUNDARY WILL REMAIN OVER THE REGION WEDNESDAY THROUGH WEDNESDAY NIGHT...BUT THERE WILL BE LITTLE TEMPERATURE OR DEWPOINT GRADIENT ALONG IT. AN UPPER-LEVEL LOW WILL DROP SOUTH THROUGH THE GREAT LAKES AND A SHORTWAVE OUT AHEAD OF IT WILL LIKELY PASS THROUGH THE AREA WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP WEDNESDAY AFTERNOON...ESPECIALLY NEAR AND WEST OF THE BLUE RIDGE MOUNTAINS. THE CONVECTION MAY TRACK FURTHER EAST INTO THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS WEDNESDAY EVENING AS THE SHORTWAVE MOVES THROUGH. WEDNESDAY NIGHT WILL TURN OUT WARM AND HUMID ACROSS MOST LOCATIONS. CONVECTION SHOULD DISSIPATE ACROSS MOST AREAS OVERNIGHT DUE TO THE LOSS OF DAYTIME HEATING. AREAS OF LOW CLOUDS AND FOG ARE EXPECTED OVERNIGHT. && .LONG TERM /THURSDAY THROUGH MONDAY/... THE UPPER-LEVEL LOW OVER THE GREAT LAKES WILL SWING THROUGH OUR AREA LATER THURSDAY INTO THURSDAY NIGHT...BRINGING A CHANCE FOR MORE SHOWERS AND THUNDERSTORMS. H5 PATTERN IS ENERGETIC THROUGH THE PERIOD AS THE MID ATLANTIC IS CAUGHT BETWEEN A RETROGRADING UPPER LOW EAST OF THE CANADIAN MARITIMES AND LARGE ANTI-CYCLONE OVER THE LOWER MISSISSIPPI VALLEY. THE H5 CLOSED HIGH PRESSURE WINS OUT THROUGH THE PERIOD WITH HEIGHT RISES FOR OUR AREA...BUT WITH A SERIES OF VORT MAXES MOVING SOUTHEAST FROM THE GREAT LAKES. THE SFC REFLECTION IS AN INVERTED ANTICYCLONIC RIDGE EMANATING FROM THE SFC HIGH OVER THE CANADIAN MARITIMES. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/...
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LOW CLOUDS WILL CONTINUE AT IAD-DCA-BWI-CHO THIS MORNING AND CIGS SHOULD HOLD AT MVFR LEVELS. CONDITIONS WILL IMPROVE LATER THIS MORNING AND VFR CONDITIONS ARE EXPECTED ACROSS MOST AREAS THIS AFTERNOON. ANY SHOWER OR THUNDERSTORM WILL BE CONFINED TO KCHO THIS AFTERNOON AND EVENING. MORE LOW CLOUDS AND FOG ARE POSSIBLE TONIGHT...AGAIN MAINLY ACROSS KCHO AND KMRB WHERE THERE WILL BE MORE MOISTURE. THERE IS A BETTER CHANCE FOR THUNDERSTORMS ACROSS THE TERMINALS LATER WEDNESDAY AND WEDNESDAY EVENING. LOW CLOUDS AND FOG MAY BE MORE WIDESPREAD OVERNIGHT WEDNESDAY INTO THURSDAY. MORE SHOWERS AND THUNDERSTORMS ARE POSSIBLE THURSDAY AFTERNOON AND EVENING. PERIODS OF MVFR/IFR CIGS ARE EXPECTED FROM LOW CLOUDS ASSOCIATED MARINE AIR.
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&& .MARINE...
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A WAVE OF LOW PRESSURE WILL MOVE OFF TO THE EAST TODAY. AN EASTERLY FLOW WILL CONTINUE DURING THIS TIME AND GUSTS OF 15-20KTS HAVE BEEN REPORTED ON THE LOWER TIDAL POTOMAC AND MD CHESAPEAKE BAY SOUTH OF NORTH BEACH THIS MORNING. A SCA IS IN EFFECT TODAY AS THE SFC LOW SLOWLY MOVES AWAY FROM THE WATERS. A STATIONARY BOUNDARY WILL REMAIN NEAR THE WATERS FOR WEDNESDAY AND THURSDAY. EAST TO SOUTHEAST WINDS ARE EXPECTED DURING THIS TIME...BUT WIND SPEEDS SHOULD REMAIN BELOW SCA CRITERIA. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE...MAINLY DURING THE AFTERNOON AND EVENING HOURS FOR WEDNESDAY AND THURSDAY. A BACKDOOR COLD FRONT WILL PASS THROUGH THE WATERS FRIDAY AND A NORTHEASTERLY FLOW IS EXPECTED DURING THE WEEKEND. NO MARINE HEADLINES ARE EXPECTED DURING THIS TIME.
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&& .TIDES/COASTAL FLOODING... AN ONSHORE FLOW WILL CONTINUE THROUGH TONIGHT...BUT IT WILL REMAIN WEAK. TIDAL ANOMALIES AROUND ONE-HALF FOOT ABOVE NORMAL WILL LIKELY PERSIST THROUGH TONIGHT. MINOR TIDAL FLOODING IS NOT EXPECTED WITH THE LOWER OF THE TWO HIGH TIDES THIS AFTERNOON. WATER LEVELS WILL BE CLOSE TO MINOR FLOODING THRESHOLDS DURING THE HIGH TIDE CYCLE LATE TONIGHT...BUT CURRENT THINKING IS THAT WATER LEVELS WILL REMAIN BELOW MINOR FLOODING THRESHOLDS SINCE THE ONSHORE FLOW IS WEAK. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ533- 534-537-541-543.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL/HAS SHORT TERM...BJL LONG TERM...BJL AVIATION...BJL/HAS MARINE...BJL/HAS TIDES/COASTAL FLOODING...BJL

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