Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 122341 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 741 PM EDT SAT JUL 12 2014 .SYNOPSIS...
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HIGH PRESSURE CENTERED ALONG THE VIRGINIA COAST WILL SHIFT OFFSHORE TONIGHT AND SET UP SOUTHERLY WINDS TO BEGIN THE NEW WEEK. A COLD FRONT WILL CROSS THE AREA TUESDAY. AN UPPER LEVEL LOW WILL THEN PERSIST OVER THE EASTERN UNITED STATES THROUGH LATE IN THE WEEK.
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&& .NEAR TERM /TONIGHT/...
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DIURNAL DOWNTREND IN COVERAGE THIS EVENING. MID LEVEL CLOUDS PERSIST...WHICH ALONG WITH RETURN FLOW MAKE FOR A WARM NIGHT...MIN TEMPS MU 60S INLAND...LM 70S URBAN AND NEAR SHORE.
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&& .SHORT TERM /SUNDAY MORNING THROUGH MONDAY/... SUNDAY...HOTTER AND MORE HUMID THAN SATURDAY. EXPECTED GREATER COVERAGE AND STRONGER THUNDERSTORMS. MAX TEMPS AROUND 90F NORTH/WEST/SOUTHWEST OF THE DC METRO...WITH LOW 90S NRN VA AND CENTRAL/SRN MD INCLUDING BALT/WASH METRO. STILL LITTLE SHEAR TO MAINTAIN STORMS...BUT ONCE THE CAP IS BROKEN...EXPECT MULTICELL DEVELOPMENT TO BE MAINTAINED. WEAK COLD FRONT APPROACHES SUNDAY NIGHT WITH SHEAR INCREASING OVERNIGHT AND ALLOWING A NOCTURNAL THUNDERSTORM THREAT. CHC/LIKELY POPS SPREAD IN FROM THE WEST AFTER MIDNIGHT. THE COLD FRONT STALLS OVER THE AREA MONDAY WITH LIKELY POPS FOR THUNDERSTORMS DUE TO STRONG MOISTURE INFLUX FROM BERMUDA HIGH AND FRONTAL BOUNDARY DRIFTING/STALLED OVER THE AREA. SLIGHT RISK FOR AREA IS JUSTIFIED WITH LIFTED INDEX -4 TO -6C. BULK SHEAR IS STILL WEAK...WITH THE THE UPR JET NOT APPROACHING UNTIL EVENING. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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A STALLED FRONT ACROSS EASTERN MARYLAND AND CENTRAL VIRGINIA WILL BECOME THE FOCAL BOUNDARY FOR ANOTHER ROUND OF FREQUENT SHOWERS AND STRONG THUNDERSTORMS EVERYWHERE TUESDAY AND IN THE EASTERN AREAS INTO TUESDAY EVENING. WITH THE MAIN UPPER LEVEL ENERGY PUSH EXPECTED LATER TUESDAY AFTERNOON AND TUESDAY NIGHT...THE INSTABILITY AHEAD OF THE FRONT AND THE UPPER LEVEL WIND ENERGY WILL QUICKLY ALLOW SHOWERS AND THUNDERSTORMS TO DEVELOP ACROSS THE REGION. VERY HEAVY RAINFALL WITH ANY ACTIVITY. RELATIVELY STEEP LAPSE RATES COULD TRANSLATE TO DAMAGING WINDS WITH THE STRONGEST THUNDERSTORMS. TEMPERATURES WILL TOP OUT NEAR 90 BEFORE THE SHOWERS AND THUNDERSTORMS BECOME FREQUENT. MUCH OF THE SHOWER AND THUNDERSTORM ACTIVITY WILL PUSH TO THE I-95 CORRIDOR...SOUTHERN MARYLAND AND ADJACENT CHESAPEAKE BAY TUESDAY EVENING. MORE STABLE AIR WILL BE USHERED INTO THE REGION FROM THE NORTHWEST AS HIGH PRESSURE BUILDS SOUTHEASTWARD. TEMPERATURES WILL BE 7 TO 10 DEGREES COOLER WEDNESDAY. A PLEASANT NIGHT IS IN STORE WEDNESDAY NIGHT WITH TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL WITH DRY AIR SETTLING IN FROM THE NORTHWEST. THERE IS A SLIGHT CHANCE OF A FEW RAIN SHOWERS IN THE POTOMAC HIGHLANDS AND SHENANDOAH VALLEY THURSDAY AFTERNOON AND THURSDAY NIGHT AS WE WILL SEE SOME WEAK UPPER LEVEL ENERGY MOVE ACROSS FROM THE WEST AND A SLIGHT ONSHORE AND UPSLOPE FLOW DEVELOP WITH A SURFACE HIGH SITTING JUST OFFSHORE. TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL WITH HIGHS IN THE LOWER 80S AND LOWS IN THE UPPER 50S. WE INCREASE THE CHANCE OF SHOWERS AND THUNDERSTORMS FRIDAY AND SATURDAY AS THE HIGH OFFSHORE USHERS IN MORE HUMID AND WARM AIR FROM THE ATLANTIC AND SOUTHEAST AND A CONTINUOUS STREAM OF UPPER LEVEL ENERGY PUSHES IN FROM THE WEST AND SOUTHWEST. TEMPERATURES FRIDAY SHOULD BE SLIGHTLY BELOW NORMAL OR NEAR NORMAL...BUT BY SATURDAY...TEMPERATURES MAY WORK THEIR WAY ABOVE NORMAL.
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&& .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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VFR TNGT. GREATER THUNDERSTORM COVERAGE SUNDAY AND CONTINUES SUNDAY NIGHT. HEAVY SHOWERS AND STRONG THUNDERSTORMS COULD BRING DIMINISHED CONDITIONS TO ANY TERMINAL TUESDAY. ASIDE FROM STRONG WIND GUSTS IN SHOWERS AND THUNDERSTORMS...SOUTHWEST TO WESTERLY WINDS WILL AVERAGE LESS THAN 10 KNOTS WITH GUSTS TO 15 KNOTS TUESDAY BUT SHOULD VEER AROUND TO THE NORTHWEST AND NORTH- NORTHWEST TUESDAY NIGHT WITH FRONTAL PASSAGE. HIGH PRES BLDG INTO THE RGN WED.
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&& .MARINE...
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SLY FLOW 10-15 KT INCREASES TO 20 KT OVER THE MAIN CHANNEL THROUGH TONIGHT. SCA UP UNTIL 6AM SUNDAY. ANOTHER SCA LATE SUNDAY AFTERNOON THROUGH SUNDAY EVENING. A COLD FRONT APPROACHES LATE SUNDAY NIGHT THROUGH MONDAY...WITH LIKELY STRONG THUNDERSTORMS BY LATE MONDAY. SECONDARY COLD FRONT TUESDAY WITH MORE STRONG THUNDERSTORM THREATS. NO HAZARD MARINE CONDITIONS EXPECTED TUESDAY THROUGH WEDNESDAY.
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&& .TIDES/COASTAL FLOODING... WATER LEVELS ARE STILL ONLY A COUPLE TENTHS FOOT ABOVE THE ASTRONOMICAL PREDICTION THIS AFTERNOON. THIS ANOMALY WILL INCREASE TO AROUND THREE QUARTERS FOOT AS SOUTHERLY FLOW STRENGTHENS INTO TONIGHT. THIS MODEST INCREASE AND A FULL MOON SOON WILL ALLOW WATER LEVELS TO APPROACH MINOR FLOODING THRESHOLDS AT SENSITIVE SITES LIKE ANNAPOLIS DURING THE PREFERRED SUNDAY MORNING HIGH TIDE. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SUNDAY FOR ANZ531>534-537- 539>541-543. SMALL CRAFT ADVISORY FROM 3 PM SUNDAY TO 2 AM EDT MONDAY FOR ANZ532>534-537-540-541-543.
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&& $$ UPDATE...WOODY! PRVS...BAJ/KLW

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