Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210752 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 352 AM EDT MON APR 21 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH TODAY. HIGH PRESSURE WILL SLOWLY SLIDE EAST TONIGHT AND A COLD FRONT WILL PASS THROUGH THE AREA TUESDAY AFTERNOON AND EVENING. HIGH PRESSURE WILL RETURN FOR WEDNESDAY AND THURSDAY BEFORE MOVING OFF THE COAST FRIDAY. A COLD FRONT WILL PASS THROUGH THE AREA SATURDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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A CLEAR AND NEARLY CALM NIGHT ACROSS THE MID ATLC REGION. THE UPPER LOW THAT HAS BEEN HANGING OUT OVER THE SRN ATLC STATES IS STILL THERE ATTM...BUT WILL SLOWLY BE PUSHED OUT TO SEA OVER THE COURSE OF THE DAY. BETWEEN THIS FEATURE AND AN AREA OF HIGH PRESSURE NOW MOVING OFF THE NEW ENGLAND COASTLINE...A THIN CORRIDOR OF TIGHTER PRES GRADIENT EXISTS AND TAPERS OFF OVER DELMARVA. WINDS ALONG THIS CORRIDOR WERE STRONGER EARLIER AND CONTINUE TO BE DOWN ACROSS THE VA TIDEWATER AND NC COAST...BUT HAVE LARGELY SUBSIDED UP ACROSS OUR CWA. TEMPS ACROSS THE AREA HAVE DROPPED INTO THE U30S...W/ ROOM FOR A FEW MORE DEGREES BY SUNRISE AS DEWPOINTS HOVER IN THE L-M30S. PATCHY FROST DEVELOPMENT EXPECTED ACROSS MUCH OF THE VA/MD PIEDMONT AND THE PORTIONS OF THE METRO AREAS SURROUNDING DC/BALT. THE FROST ADVISORY HAS BEEN EXPANDED FROM NERN MD DOWN ACROSS MUCH OF THE AREA E OF THE BLUE RIDGE THRU 8AM. AFTER THE RELATIVELY COLD START TO THE DAY...TEMPS WILL AGAIN RISE QUICKLY BACK INTO THE 60S OVER THE COURSE OF THE MRNG AND INTO THE EARLY AFTN. CLEAR SKIES WILL LAST THROUGH MUCH OF THE DAY...AS THE SRN ATLC LOW SLOWLY MOVES OUT TO SEA AND THE NEXT WX-MAKER SLIDES TOWARD THE AREA FROM THE WEST. SOME OF THE CIRRUS DEBRIS FROM THIS INCOMING SHORTWAVE WILL ARRIVE LATE THIS AFTN AS TEMPS REACH THE U60S/L70S. WINDS TODAY WILL BE LIGHT AS A WEAK IN-SITU SFC HIGH BUILDS OVER THE AREA IN BETWEEN THE TWO SURROUNDING SYSTEMS... TURNING SLY OVERNIGHT AS THE HIGH IS PUSHED OFF THE COAST. THE INCREASE IN CLOUD COVER TONIGHT AND LOW LEVEL MOISTURE WILL MODERATE TEMPS TO ONLY DROP INTO THE U40S/L50S - A GOOD 10-15F DEG WARMER THAN TONIGHT`S LOW TEMPS.
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&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
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WEAK HIGH PRESSURE WILL CONTINUE TO MOVE OFF THE COAST TUESDAY WHILE A COLD FRONT OVER THE OHIO VALLEY TUESDAY MORNING PASSES THROUGH OUR AREA TUESDAY AFTERNOON AND EVENING. A SOUTHERLY FLOW AHEAD OF THE FRONT WILL ALLOW FOR WARMER CONDITIONS...DESPITE CLOUD COVER ASSOCIATED WITH THE FRONTAL PASSAGE. MAX TEMPS WILL RANGE FROM THE LOWER 60S IN THE MOUNTAINS TO NEAR 80 IN THE VIRGINIA PIEDMONT. THE COMBINATION OF WARMER AIR AND INCREASING DEWPOINTS FROM THE SOUTHERLY FLOW WILL BE ENOUGH TO CAUSE AN UNSTABLE ATMOSPHERE. HOWEVER...INSTABILITY WILL BE LIMITED WITH DEEP MOISTURE REMAINING OFF TO OUR SOUTH. MOST OF THE DYNAMICS WITH THIS SYSTEM WILL BE TO OUR NORTH...BUT THERE SHOULD BE ENOUGH FORCING WITH THE FRONT TO COMBINE WITH THE INSTABILITY...CAUSING SOME SHOWERS ALONG AND AHEAD OF THE FRONT. A FEW THUNDERSTORMS CANNOT BE RULED OUT AS WELL. HOWEVER...ANY SEVERE THREAT WILL BE EXTREMELY LIMITED DUE TO THE LOW INSTABILITY. THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS WILL BE FROM MID-MORNING THROUGH EARLY AFTERNOON WEST OF THE BLUE RIDGE MOUNTAINS...AND DURING THE AFTERNOON HOURS EAST OF THE BLUE RIDGE MOUNTAINS. THE FRONT WILL MOVE OFF TO OUR EAST TUESDAY EVENING. ANY LEFTOVER SHOWERS ACROSS EXTREME SOUTHERN MARYLAND WILL END DURING THIS TIME. A NORTHWEST FLOW WILL USHER IN COOLER AND DRIER CONDITIONS FOR TUESDAY NIGHT. MIN TEMPS WILL RANGE FROM THE 20S ALONG THE RIDGE TOPS OF THE ALLEGHENY HIGHLANDS TO NEAR 50 IN DOWNTOWN WASHINGTON AND BALTIMORE.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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LOW PRESSURE WILL INTENSIFY NEAR NOVA SCOTIA WEDNESDAY WHILE HIGH PRESSURE BUILDS TOWARD THE REGION FROM THE GREAT LAKES. THE PRESSURE GRADIENT BETWEEN THESE SYSTEMS WILL CAUSE GUSTY NORTHWEST WINDS...AND MAX TEMPS WILL BE BELOW CLIMO DUE TO THE COLD ADVECTION ASSOCIATED WITH THE NORTHWEST FLOW. HIGH PRESSURE WILL BUILD OVERHEAD WEDNESDAY NIGHT...CAUSING DRY AND CHILLY CONDITIONS. HIGH PRESSURE WILL CONTINUE TO CONTROL THE WEATHER PATTERN THURSDAY BEFORE MOVING OF THE COAST FRIDAY. A RETURN FLOW AROUND THE HIGH WILL CAUSE WARMER CONDITIONS LATE IN THE WEEK BEFORE ANOTHER COLD FRONT PASSES THROUGH SATURDAY. CHILLIER CONDITIONS ARE EXPECTED BEHIND THIS BOUNDARY EARLY NEXT WEEK.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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VFR CONDS TODAY/TONIGHT. THE OFFSHORE UPPER LOW JUST EAST OF THE CAROLINAS WILL FINALLY MOVE OUT TO SEA AFTER BEING STATIONED OVER THE SRN ATLC STATES FOR THE PAST FEW DAYS. SOME FROST FORMATION POSSIBLE IN THE NEXT FEW HRS...AS WINDS DROP OFF AND SO DO TEMPS - HOVERING IN THE MIDDLE 30S THRU DAWN. LIGHT WINDS WILL BE THE MAIN STORY TODAY...W/ CLEAR SKIES AS HIGH PRESSURE REMAINS OVERHEAD BUT WILL MOVE OFF THE COAST LATE TONIGHT JUST AHEAD OF THE NEXT WAVE OF LOW PRESSURE. VFR CONDITIONS ARE EXPECTED MOST OF THE TIME TUESDAY THROUGH FRIDAY. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE TUESDAY AND CIGS/VSBYS MAY BRIEFLY BE REDUCED IN ANY CONVECTION. NORTHWEST WINDS WILL INCREASE BEHIND A COLD FRONT TUESDAY NIGHT AND WEDNESDAY. THE STRONGEST WINDS ARE EXPECTED WEDNESDAY WITH GUSTS AROUND 30 KNOTS. HIGH PRESSURE WILL BUILD OVERHEAD WEDNESDAY NIGHT AND THURSDAY...CAUSING WINDS TO DECREASE. A SOUTHERLY FLOW IS EXPECTED FRIDAY AS THE HIGH MOVES OFF THE COAST.
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&& .MARINE...
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HIGH PRESSURE WILL SUPPLY LIGHT WINDS FOR THE WATERS TODAY...THOUGH STILL SOME 10-15KT BREEZES FROM THE MIDDLE-TO-LOWER PORTION OF THE BAY. THESE CONDITIONS WILL GENERALLY CONTINUE THRU THE FIRST-HALF OF THE DAY...WHILE AN OFFSHORE UPPER LOW OFF THE CAROLINAS SLOWLY MOVES EAST. WINDS WILL THEN DROP OFF LATER TONIGHT AND SWITCH TO A SLY FLOW AS THE HIGH PRES MOVES OFF THE MID ATLC COAST. A COLD FRONT WILL PASS THROUGH THE WATERS LATE TUESDAY AFTERNOON AND EVENING. A FEW SHOWERS AND THUNDERSTORMS ARE POSSIBLE AHEAD OF THE FRONT TUESDAY AFTERNOON AND EARLY EVENING. ANY THUNDERSTORMS THAT DO DEVELOP WILL BE CAPABLE OF PRODUCING GUSTY WINDS. NORTHWEST WINDS WILL INCREASE BEHIND THE COLD FRONT TUESDAY NIGHT. GUSTY NORTHWEST WINDS WILL CONTINUE INTO WEDNESDAY EVENING BEFORE GRADUALLY DECREASING WEDNESDAY NIGHT. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR THE WATERS TUESDAY NIGHT INTO WEDNESDAY NIGHT. THE STRONGEST WINDS ARE EXPECTED WEDNESDAY WITH GUSTS AROUND 30 KNOTS. HIGH PRESSURE WILL BUILD OVERHEAD LATE WEDNESDAY NIGHT AND THURSDAY BEFORE MOVING OFF THE COAST FRIDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR DCZ001. MD...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MDZ004>007- 009>011-013-014-016. VA...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR VAZ042-050>057- 501-502. WV...NONE. MARINE...NONE.
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&& $$ SYNOPSIS...BJL NEAR TERM...GMS SHORT TERM...BJL LONG TERM...BJL AVIATION...BJL/GMS MARINE...BJL/GMS

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