Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 271135 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 735 AM EDT SUN JUL 27 2014 .SYNOPSIS... LOW PRESSURE OVER MINNESOTA IS EXPECTED TO TRACK ACROSS PENNSYLVANIA TONIGHT. AN ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION MONDAY. HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING COOLER AND DRIER CONDITIONS DURING MIDWEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... UPDATE...COASTAL FLOOD ADVISORY FOR ANNE ARUNDEL COUNTY IS CANCELED. A SERIES OF UPPER-LEVEL DISTURBANCES ARE LOCATED IN THE WESTERLY FLOW ALOFT. ONE IS OVERHEAD EARLY THIS MORNING WHILE ANOTHER ONE IS TRACKING THROUGH THE OHIO VALLEY. A SOUTHERLY FLOW AROUND HIGH PRESSURE OVER THE ATLANTIC HAS USHERED IN MORE MOISTURE...CAUSING INSTABILITY TO INCREASE. THE COMBINATION OF INCREASED INSTABILITY AND FORCING FROM THE UPPER-LEVEL DISTURBANCES HAS TRIGGERED SOME SHOWERS AND THUNDERSTORMS. THE FIRST DISTURBANCE WILL MOVE OFF TO OUR EAST EARLY THIS MORNING...BUT THE OTHER ONE IS EXPECTED TO PASS THROUGH OUR AREA LATER THIS MORNING INTO EARLY THIS AFTERNOON...BRINGING MORE SHOWERS AND THUNDERSTORMS. AS OF NOW...IT APPEARS THAT ANY THREAT FOR SEVERE THUNDERSTORMS THIS MORNING INTO EARLY THIS AFTERNOON WILL BE LIMITED DUE TO CLOUD COVER...MARGINAL PROFILES AND PRECIPITATION KEEPING INSTABILITY SOMEWHAT LIMITED. HOWEVER...THERE MAY BE A BREAK IN THE ACTION AS THE UPPER-LEVEL DISTURBANCE MOVES OFF TO OUR EAST THIS AFTERNOON. THERE SHOULD AT LEAST BE SOME BREAKS OF SUNSHINE...AND WITH DEWPOINTS IN THE UPPER 60S AND 70S...THIS SHOULD BE ENOUGH TO CAUSE MODERATE AMOUNTS OF INSTABILITY TO DEVELOP. NAM/GFS BUFKIT ARE INDICATING BETWEEN 1000 AND 2000 J/KG OF MLCAPE LATER THIS AFTERNOON INTO THIS EVENING. A POTENT SHORTWAVE AND COLD FRONT WILL TRACK INTO THE OHIO VALLEY THIS EVENING. THIS WILL STRENGTHEN THE UPPER-LEVEL AND LOWER-LEVEL FLOW OVER OUR AREA...CAUSING SHEAR PROFILES TO BE HIGHLY FAVORABLE FOR SEVERE THUNDERSTORMS. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BREAK OUT AHEAD OF THE COLD FRONT OVER THE OHIO VALLEY INTO WEST VIRGINIA THIS AFTERNOON...AND THIS ACTIVITY WILL LIKELY SPREAD THROUGH OUR AREA LATER THIS AFTERNOON AND EVENING. THIS IS GOING TO BE THE TIME WHEN SEVERE WEATHER IS MOST LIKELY...WHICH WOULD BE LATER THIS AFTERNOON INTO EARLY THIS EVENING WEST OF THE BLUE RIDGE MOUNTAINS AND THIS EVENING EAST OF THE BLUE RIDGE MOUNTAINS. HOWEVER...KEEP IN MIND THAT SEVERE STORMS OUT AHEAD OF THIS LINE MAY DEVELOP ACROSS ALL AREAS THIS AFTERNOON. THE COMBINATION OF THE INSTABILITY...SHEAR PROFILES AND LIFTING MECHANISMS SUCH AS OUTFLOW BOUNDARIES...A SURFACE TROUGH AND THE APPROACHING COLD FRONT WILL ENHANCE THE THREAT FOR SEVERE THUNDERSTORMS. IN FACT SUPERCELLS WITH SIGNIFICANT SEVERE WEATHER IS POSSIBLE THIS AFTERNOON AND EVENING IF THE INGREDIENTS ALL COME TOGETHER. DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES WILL BE THE PRIMARY THREATS ALONG WITH VERY HEAVY RAINFALL. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... THE POTENT SHORTWAVE WILL MOVE INTO UPSTATE NEW YORK LATER TONIGHT WHILE THE POTENT COLD FRONT LIKELY JUMPS TO THE PRESSURE TROUGH OFF TO OUR EAST BY MONDAY MORNING. THE DRY SLOT ALONG WITH COLD ADVECTION SHOULD SUPPRESS CONVECTION LATE TONIGHT. MIN TEMPS WILL RANGE FROM THE 50S IN THE ALLEGHENY HIGHLANDS TO THE LOWER AND MIDDLE 70S IN WASHINGTON AND BALTIMORE. && .LONG TERM /MONDAY THROUGH SATURDAY/... THE NEXT 24 HRS LOOK TO BE VERY ACTIVE WX WISE...WITH A DOWNWARD TREND IN ACTIVITY EXPECTED THEREAFTER. CD FNT LOOKS TO BE MOVING OFFSHORE MIDDAY MON...BRINGING AN END TO THE CNVCTV CHCS AND USHERING IN THE COOLER AIR THAT WL END WHAT IS TYPICALLY THE HOTTEST TIME IN THE HOTTEST MONTH OF THE YR (CLIMATOLOGICALLY TEMPS BEGIN TO DROP IN EARLY AUG). BRZY CONDS AREA XPCTD MON AFTN. AFTR THAT SVRL DAYS OF M CLR SKIES W/ COMFORTABLE TEMPS ARE XPCTD. DWPTS IN THE 50S...HARD NOT TO ENJOY THAT IN JUL. HIGH TEMPS TUE-THU SHOULD BE IN THE LM80S (COOLER IN THE MTNS) W/ LOWS IN THE MU50S. (WARMER IN THE CITIES). NO REALLY HOT WX ON TAP FOR THE MID ATLC RGN. AS HAS BEEN DISCUSSED B4 THE PRIMARY REASON FOR THIS IS THE UPR LVL WRN RDG/ERN TROF. DRY AND HOT IN THE W - NW ICC WEB SITE SHOWS MULTIPLE WILDFIRES ONGOING IN OR/WA - W/ 2 IN WA BEING ESPECIALLY LARGE. THIS PATTERN LOOKS TO RMN IN PLACE UNTIL AT LEAST NEXT WKND. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH THIS EVENING. THUNDERSTORMS MAY BECOME SEVERE...ESPECIALLY LATER THIS AFTERNOON AND EVENING. DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES ARE POSSIBLE. CIGS/VSBYS WILL BE REDUCED TO MVFR/IFR LEVELS BRIEFLY DURING TIMES OF CONVECTION. CONVECTION SHOULD DISSIPATE OVERNIGHT AS A COLD FRONT MOVES OFF TO OUR EAST. CD FNT WL CROSS THE AREA MON MRNG. LINGERING SHOWERS/ANY LOWER CIGS SHOULD IMPROVE BY AFTN THEN GUSTY NWRLY WINDS. THESE SHOULD DIMINISH BY EVE. VFR CONDS MON NGT THRU THU. && .MARINE... A SOUTHERLY FLOW WILL CONTINUE THROUGH TONIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE WATERS THIS AFTERNOON AND EVENING. IT WILL BE MARGINAL DUE TO RELATIVELY COOLER WATERS...BUT A STRENGHENING PRESSURE GRADIENT AND WIND FIELD SHOULD CAUSE GUSTS AROUND 20 KNOTS. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR LATE TONIGHT ALONG THE MARYLAND CHESAPEAKE BAY FROM SANDY POINT TO SMITH POINT AND THE LOWER TIDAL POTOMAC RIVER FROM COBB ISLAND TO SMITH POINT. ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH TONIGHT. SEVERE THUNDERSTORMS ARE A CONCERN...ESPECIALLY LATER THIS AFTERNOON THROUGH THIS EVENING. DAMAGING WINDS...LARGE HAIL AND ISOLATED WATERSPOUTS ARE POSSIBLE. PLEASE PAY ATTENTION TO THE LATEST FORECASTS REGARDING WATCHES AND WARNINGS FOR SEVERE WEATHER. SCA IN EFFECT FOR ALL OF THE WATERS DURG THE DAY MON AS A CD FNT MOVES OFFSHORE AND WNW WINDS STRENGTHEN. NO PROBS FORESEEN MON NGT-MIDWK. && .TIDES/COASTAL FLOODING... A SOUTHERLY FLOW HAS CAUSED TIDAL ANOMALIES BETWEEN ONE HALF AND ONE FOOT ABOVE NORMAL EARLY THIS MORNING. WILL HAVE TO KEEP AN EYE ALONG THE UPPER TIDAL POTOMAC SHORE NEAR WASHINGTON DC. AT THIS TIME...THE FLOW APPEARS THAT IT IS LIGHT ENOUGH FOR WATER LEVELS TO REMAIN JUST BELOW MINOR FLOODING THRESHOLDS NEAR HIGH TIDE THIS MORNING. THE HIGH TIDE THIS AFTERNOON WILL BE THE LOWER OF THE TWO...SO NO TIDAL FLOODING IS EXPECTED. THE FLOW WILL BEGIN TO TURN OFFSHORE LATE TONIGHT SO ANOMALIES SHOULD COME DOWN A BIT. THEREFORE...TIDAL FLOODING IS NOT EXPECTED. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR ANZ530-531-535-536-538-539-542. SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT MONDAY FOR ANZ530- 531-535-536-538-539-542. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 7 PM EDT MONDAY FOR ANZ532>534-537-540-541-543. && $$ UPDATE...HAS PREVIOUS DISCUSSION...BJL/WOODY!

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