Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 010759 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 359 AM EDT FRI AUG 1 2014 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH SATURDAY/...
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CYCLONIC FLOW ALOFT CONTINUES ACROSS A MAJORITY OF THE US WITH THE 500MB TROUGH AXIS NEAR THE MISSISSIPPI RIVER VALLEY. THE MID-ATLANTIC IS THEREFORE ON THE LEE SIDE OF THE TROUGH WHERE SOUTHERLY FLOW ADVECTS MOISTURE INTO THE REGION. A STATIONARY FRONT RESIDES PARALLEL AND EAST OF THE EAST COAST. HIGH PRESSURE IS LOCATED OFF THE NEW JERSEY COAST. AN UPPER LEVEL DISTURBANCE WILL APPROACH THE MID-ATLANTIC THIS MORNING. SHOWERS ACROSS NC/VA WILL CONTINUE TO MOVE NORTHWARD AND SPREAD ACROSS THE FOOTHILLS THIS MORNING. THIS ACTIVITY WILL REACH THE DC METRO BY AFTERNOON. STABLE CONDITIONS DUE TO COOLER AIR AT THE SFC HAS LIMITED ANY CHANCE OF THUNDER THIS MORNING. MOISTURE WILL INCREASE TODAY. WEAK INSTABILITY IS EXPECTED ACROSS THE POTOMAC HIGHLANDS THIS AFTERNOON AND A ISOLATED THUNDERSTORM IS POSSIBLE WEST OF THE BLUE RIDGE. FCST MAX TEMPS WILL BE WELL BELOW NORMAL TODAY DUE TO THE CLOUDY AND WET CONDITIONS. TEMPS IN THE UPPER 70S TO 80 ARE EXPECTED WITH THE UPPER 60S IN THE HIGHER ELEVATIONS OF THE CENTRAL FOOTHILLS. THE STATIONARY FRONT OFF THE EAST COAST WILL MOVE WESTWARD AND APPROACH THE REGION BY THIS AFTERNOON. THIS CONVERGENCE COUPLED WITH MULTIPLE DISTURBANCES MOVING OVERHEAD IN THE SW FLOW ALOFT THIS AFTERNOON WILL LEAD TO MODERATE TO HEAVY RAIN ACROSS SERN VA INTO SRN MD BY EVENING. AROUND A INCH OF RAIN IS EXPECTED ACROSS THE AREA. 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/...
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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.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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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.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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SHRA WILL MOVE INTO THE REGION TODAY IMPACTING CHO THIS MORNING AND DCA-BWI-MTN BY AFTERNOON. ISO TSRA IS POSSIBLE AT MRB THIS AFTERNOON. VFR CONDITIONS EXPECTED THIS MORNING AS CLOUDS INCREASE FROM SOUTH TO NORTH. MVFR CONDITIONS POSSIBLE THIS AFTERNOON AS CLOUDS LOWER...AT THIS TIME THINK IT WILL BE SCT. 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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SCA WAS CANCELLED AS WINDS WERE NOT MIXING DOWN TO THE SFC. S WINDS 10-15 KTS WILL CONTINUE THIS MORNING BEFORE TAPERING OFF BY EARLY AFTERNOON. WINDS WILL BECOME EASTERLY LATE TONIGHT AND SCA IS POSSIBLE AS A FRONT RESIDES ACROSS THE REGION TONIGHT. SHOWERS ARE EXPECTED TODAY AND 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...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...HAS/BPP NEAR TERM...HAS SHORT TERM...BPP LONG TERM...BPP AVIATION...HAS/BPP MARINE...HAS/BPP

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