Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 011412 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1012 AM EDT FRI AUG 1 2014 .SYNOPSIS... A FRONTAL BOUNDARY WILL REMAIN NEAR THE COAST THROUGH THE WEEKEND. A TROUGH IS EXPECTED TO MOVE THROUGH MONDAY. WEAK HIGH PRESSURE BUILDS IN TUESDAY. && .NEAR TERM /THROUGH SATURDAY/...
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ANALYSIS LATE THIS MORNING SHOWS A COASTAL FRONT ALONG THE MID- ATLANTIC COAST AND AN UPPER-LEVEL DISTURBANCE MOVING THROUGH NORTH CAROLINA AND SOUTHERN VIRGINIA. SURFACE HIGH PRESSURE REMAINS ALONG THE NEW ENGLAND COAST AND IT EXTENDS TOWARD THE MID-ATLANTIC COAST. THE UPPER-LEVEL DISTURBANCE WILL MOVE THROUGH THE AREA THIS AFTERNOON WHILE THE COASTAL FRONT SLOWLY TRACKS NORTH AND WEST TOWARD THE MID-ATLANTIC COAST. WARM AND MOIST AIR WILL OVERRUN THE RELATIVELY COOLER AIR IN PLACE. THE COMBINATION OF ISENTROPIC LIFT AND FORCING FROM THE UPPER-LEVEL DISTURBANCE SHOULD CAUSE THE RAIN OVER CENTRAL VIRGINIA TO SPREAD NORTHWARD INTO THE REST OF THE CWA. MAX TEMPS WILL BE QUITE COOL FOR THIS TIME OF YEAR DUE TO THE RAIN AND EXTENSIVE CLOUD COVER. MAX TEMPS WILL RANGE FROM THE 60S IN THE MOUNTAINS TO THE UPPER 70S AND LOWER 80S IN WASHINGTON AND BALTIMORE. THERE MAY BE A LULL IN THE PRECIPITATION THIS EVENING AS THE DISTURBANCE MOVES OFF TO NORTH...BUT POCKETS OF LIGHT RAIN ARE STILL POSSIBLE AS WARM AND MOIST AIR CONTINUES TO OVERRUN THE COOLER AIR IN PLACE. ANOTHER DISTURBANCE WILL PASS THROUGH THE REGION LATER TONIGHT...BRINGING A BETTER CHANCE FOR RAIN. THE BEST CHANCE FOR RAIN WILL BE NEAR AND EAST OF INTERSTATE 95 CLOSER TO THE COASTAL FRONT. THE STATIONARY FRONT WILL REMAIN NEAR THE DELMARVA PENINSULA SATURDAY AND SHOWERS ARE EXPECTED ACROSS SRN MD THROUGH THE DAY. CLOUDY CONDITIONS WILL CONTINUE ELSEWHERE SATURDAY AS HIGH PRESSURE NOSES INTO THE MID ATLANTIC AND MOISTURE LINGERS AHEAD OF THE TROUGH. ALTHOUGH SHOWERS WILL BE LIKELY NEAR THE STATIONARY FRONT ALL DAY...ISO-SCT SHOWERS WILL BE POSSIBLE ACROSS THE REGION SATURDAY AS SW FLOW MOVES ACROSS COOLER AIR. TEMPS WILL STAY WELL BELOW NORMAL AND SIMILAR TO TODAY...UPPER 70S TO NEAR 80 AND LOW 70S IN THE MTNS.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... BOUNDARY IS FORECAST TO REMAIN NEARLY STATIONARY ALONG THE COAST THROUGH THE WEEKEND...AS AN UPPER TROUGH APPROACHES FROM THE WEST. COMBINATION OF A WAVE OF LOW PRESSURE ALONG THE FRONT AND ALSO PVA/SHORTWAVE ENERGY AHEAD OF THE TROUGH WILL KEEP UNSETTLED CONDITIONS DURING THIS TIME ALONG WITH BELOW CLIMO MAXIMA AND NEAR CLIMO MINIMA. && .LONG TERM /MONDAY THROUGH THURSDAY/... UNCERTAINTY EXISTS WITH THE TIMING OF THE TROUGH. GFS SUGGESTS SLOWER AND THUS A CHANCE OF SHOWERS/THUNDERSTORMS MONDAY. ECMWF IS A LITTLE FASTER WITH MUCH OF THE PRECIP OFFSHORE. ENSEMBLE APPROACH IS SOMEWHERE IN BETWEEN AND REFLECTED IN THE FORECAST. TROUGH IS FORECAST TO HAVE EXITED BY TUESDAY FOR DRY CONDITIONS. WE/LL BE KEEPING AN EYE ON TROPICAL STORM BERTHA WHICH IS FORECAST TO BE ACROSS THE WESTERN ATLANTIC BY TUESDAY EVENING. MODELS ALSO SHOW A FRONT DIVING SOUTH WEDNESDAY INTO THURSDAY FOR ANOTHER CHANCE OF SHOWERS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/...
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RAIN WILL OVERSPREAD THE TERMINALS THIS AFTERNOON. THE MOST WIDESPREAD PRECIPITATION WILL BE ACROSS KCHO AND THE EASTERN TERMINALS. SUBVFR CONDITIONS ARE POSSIBLE IN PERIODS OF RAIN. SHRA POSSIBLE TONIGHT AND THROUGH SATURDAY...AT THIS TIME CONFIDENCE IS LOW ON TIMING AS SHOWERS SHOULD BE ISO-SCT AT THE TERMINALS SATURDAY. IFR CIGS EXPECTED AT CHO/MRB BY EARLY SAT MORNING AND MVFR AT IAD. POTENTIAL EXISTS FOR LOW CIGS TO DEVELOP SATURDAY NIGHT INTO SUNDAY. UNSETTLED CONDITIONS COULD CONTINUE INTO MONDAY UNTIL A TROUGH MOVES BY AND PUSHES A FRONT NEAR THE COAST FURTHER OFFSHORE.
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&& .MARINE...
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WINDS WILL BECOME SOUTHEAST THIS AFTERNOON...BUT REMAIN BELOW SCA CRITERIA. WINDS BECOME EASTERLY TONIGHT AND WIND GUSTS MAY APPROACH 20 KNOTS AS A FRONT APPROACHES THE WATERS. RAIN IS EXPECTED TODAY AND MORE SHOWERS WILL CONTINUE THROUGH SATURDAY ESPECIALLY FOR THE LOWER TIDAL POTOMAC AND MD CHESAPEAKE BAY SOUTH OF SANDY POINT. SOUTHEAST WINDS SATURDAY NIGHT INTO SUNDAY MAY TURN MORE NORTHEAST EARLY NEXT WEEK. GRADIENT MAINLY LIGHT THROUGH THEN...BUT SOUTHEAST WINDS MAY BE 10 TO 15 KT UP THE BAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...BPP/HAS NEAR TERM...BJL/HAS SHORT TERM...BPP LONG TERM...BPP AVIATION...BJL/BPP/HAS MARINE...BJL/BPP/HAS

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