Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 230141 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 941 PM EDT WED APR 22 2015 .SYNOPSIS... COOLER AND DRIER AIR WILL FOLLOW A STRONG COLD FRONT AS IT MOVES OFF THE COAST THIS EVENING. HIGH PRESSURE WILL BUILD IN FOR THE END OF THE WEEK...BUT STILL KEEP BREEZY CONDITIONS OCCURRING EACH OF THE NEXT COUPLE OF DAYS. ANOTHER LOW PRESSURE SYSTEM IS EXPECTED TO MOVE THROUGH THE AREA THIS WEEKEND. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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A POTENT JETMAX WILL SWING THROUGH THE AREA LATE THIS EVENING AROUND AN UPPER-LEVEL LOW CENTERED OVER ONTARIO. STEEP LOW-LEVEL LAPSE RATES COMBINED WITH THE FORCING FROM THE TROUGH TO TRIGGER A FEW SHOWERS AND EVEN AN ISOLATED THUNDERSTORM ACROSS THE POTOMAC HIGHLANDS. AN ISOLATED SHOWER/SPRINKLE MAY MAKE IT FARTHER EAST INTO PORTIONS OF NORTHERN VIRGINIA AND NORTHERN MARYLAND LATE THIS EVENING AS THE JETMAX SWINGS THROUGH. HOWEVER...MOST OF THE TIME WILL BE DRY AND PRECIPITATION AMOUNTS IF ANY WILL BE LIGHT. A NORTHWEST FLOW WILL USHER IN CHILLY CONDITIONS BEHIND A COLD FRONT OVERNIGHT. ANY LEFTOVER SHOWERS/SPRINKLES LATE THIS EVENING SHOULD DISSIPATE BEHIND THE JETMAX OVERNIGHT. HOWEVER...AN UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW MAY RESULT IN A FEW SNOW SHOWERS ALONG AND WEST OF THE ALLEGHENY FRONT LATE TONIGHT WITH PLENTY OF COLD AIR MOVING IN ALOFT. THERE IS A CONCERN FOR SOME FROST TONIGHT...ESPECIALLY NORTH AND WEST OF INTERSTATE 95. HOWEVER...THE GRADIENT WIND WILL LIKELY REMAIN STRONG ENOUGH TO PREVENT WIDESPREAD FROST FROM DEVELOPING. THEREFORE...NO HEADLINES ARE EXPECTED AT THIS TIME. WILL MENTION PATCHY FROST IN THE FORECAST. MIN TEMPS WILL RANGE FROM THE 20S IN THE ALLEGHENY HIGHLANDS...TO THE MID AND UPPER 30S IN THE NORTHERN AND WESTERN SUBURBS OF WASHINGTON AND BALTIMORE...TO THE THE MID AND UPPER 40S IN SOUTHERN MARYLAND.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/...
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AN UPPER-LEVEL TROUGH WILL REMAIN OVERHEAD THURSDAY WITH SURFACE HIGH PRESSURE BUILDING THROUGH THE MIDWEST. A NORTHWEST FLOW WILL CONTINUE TO USHER IN CHILLY CONDITIONS FOR THIS TIME OF YEAR. A BKN STRATOCU DECK WILL DEVELOP DUE TO THE COLDER AIR ALOFT ASSOCIATED WITH THE UPPER TROUGH...BUT MOST LOCATIONS MAY END UP DRY THANKS TO LIMITED MOISTURE. HOWEVER...AN ISOLATED SHOWER/SPRINKLE CANNOT BE RULED OUT DURING THE AFTERNOON. KEPT THE MENTION OF PRECIPITATION CONFINED TO THE ALLEGHENY AND POTOMAC HIGHLANDS WHERE AN UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW WILL ENHANCE LIFT...BUT WITH A LITTLE INSTABILITY EVERYWHERE IT CANNOT BE COMPLETELY RULED OUT FARTHER EAST TOWARD THE WASHINGTON/BALTIMORE METROPOLITAN AREAS. 850 MB TEMPS WILL BE BELOW BELOW 0C THURSDAY...RESULTING IN HIGHS ONLY IN THE 50S TO AROUND 60. CHILLY OVERNIGHT TEMPERATURES WILL FOLLOW ONCE AGAIN FOR THURSDAY NIGHT WITH LOWS DROPPING BACK TO THE LOW 30S NORTH AND WEST OF THE METRO AREAS TO THE UPPER 30S TO THE LOWER 40S ACROSS THE I-95 CORRIDOR AND SOUTHERN MARYLAND. PATCHY FROST WILL BE POSSIBLE. HIGH PRESSURE WILL REMAIN IN PLACE ON FRIDAY BUT TEMPERATURES WILL REMAIN BELOW NORMAL WITH READINGS MOSTLY IN THE 50S...EXCEPT LOW 60S OVER CENTRAL VA. PATCHY FROST WILL BE POSSIBLE AGAIN FRIDAY NIGHT INTO SATURDAY MORNING. CLOUDS WILL INCREASE FROM WEST TO EAST LATE FRIDAY NIGHT AS LOW PRESSURE APPROACHES FROM THE WEST. LIGHT RAIN/SHOWERS WILL INCREASE FROM SOUTHWEST TO NORTHEAST ON SATURDAY AND CONTINUE INTO SATURDAY NIGHT.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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HIGH PRESSURE WILL RETURN FOR THE SECOND HALF OF THE WEEKEND INTO EARLY NEXT WEEK...BEFORE A STRONG TROUGH OF LOW PRESSURE APPROACHES THE AREA DURING THE MIDDLE OF NEXT WEEK.
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&& .AVIATION /01Z THURSDAY THROUGH MONDAY/...
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WEST TO NORTHWEST WINDS WILL CONTINUE TONIGHT. GUSTS AROUND 20 KNOTS ARE POSSIBLE THIS EVENING...BUT WINDS SHOULD REMAIN NEAR OR BELOW 10 KNOTS OVERNIGHT. EXPECT ANOTHER BREEZY DAY ON THURSDAY WITH WNW WINDS GUSTING AROUND 25 KT. VFR CONDITIONS THURSDAY NIGHT THROUGH FRIDAY NIGHT. MVFR OR IFR CONDITIONS POSSIBLE SATURDAY AND SATURDAY NIGHT DUE TO THE CHANCE OF LIGHT RAIN. VFR CONDITIONS SUNDAY. MAINLY VFR SUN-MON W/ NWLY FLOW 10-15 KT.
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&& .MARINE...
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WEST TO NORTHWEST WINDS WILL CONTINUE TONIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL OF THE WATERS THROUGH 2 AM...BUT IT WILL BE MARGINAL FOR THE UPPER TIDAL POTOMAC RIVER. THE SMALL CRAFT ADVISORY CONTINUES FOR THE REST OF TONIGHT THROUGH MID- MORNING THURSDAY FOR THE MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER. WINDS WILL STRENGTHEN ACROSS ALL OF THE WATERS THURSDAY AND A SMALL CRAFT ADVISORY IS IN EFFECT LATE THURSDAY MORNING INTO THURSDAY EVENING. NO MARINE HAZARDS THURSDAY NIGHT. SMALL CRAFT ADVISORIES POSSIBLE FRIDAY. NO MARINE HAZARDS FRIDAY NIGHT THROUGH SUNDAY. SCA LIKELY SUNDAY IN NWLY SURGE BEHIND FRONT.
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&& .TIDES/COASTAL FLOODING...
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A WESTERLY COMPONENT TO THE SURFACE WIND WILL CAUSE TIDAL ANOMALIES TO DECREASE THROUGH FRIDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THURSDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY UNTIL 2 AM EDT THURSDAY FOR ANZ535-536. SMALL CRAFT ADVISORY FROM 10 AM TO 8 PM EDT THURSDAY FOR ANZ535-536. && $$ SYNOPSIS...GMS NEAR TERM...BJL SHORT TERM...GMS LONG TERM...DFH AVIATION...BJL/GMS/KRW/DFH MARINE...BJL/GMS/KRW/DFH TIDES/COASTAL FLOODING...BJL

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