Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 200114 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 914 PM EDT SUN OCT 19 2014 .SYNOPSIS... HIGH PRESSURE WILL BRIEFLY PASS BY THE AREA TO THE SOUTH... USHERING IN CALM WINDS AND CLEAR SKIES THROUGH EARLY MONDAY. AN UPPER LEVEL TROUGH WILL QUICKLY DIVE DOWN THROUGH THE UPPER MIDWEST...BUT SLOW DOWN AND RESIDE OVER THE MID-ATLANTIC AND NEW ENGLAND REGIONS THROUGH MUCH OF THE COMING WEEK. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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HIGH PRESSURE WILL BUILD OVER THE AREA TONIGHT...ALLOWING FOR LIGHT WINDS ACROSS THE AREA. LIGHT WINDS AND DRY CONDITIONS WILL ALLOW FOR RADIATIONAL COOLING TONIGHT ACROSS THE ENTIRE CWA...LEADING TO CHILLY CONDITIONS. THE FROST ADVISORY HAS BEEN EXTENDED IN AREA TO INCLUDE THE NORTHERN AND WESTERN SUBURBS OF WASHINGTON AND BALTIMORE. A FREEZE WARNING REMAINS IN EFFECT FOR GRANT...PENDLETON AND HIGHLAND COUNTIES IN THE POTOMAC HIGHLANDS. THERE WILL BE SOME HIGH CLOUDS MOVING THROUGH AHEAD OF A COLD FRONT OVER THE GREAT LAKES. THIS DOES ADD TO THE UNCERTAINTY AS TO HOW MUCH FROST WILL DEVELOP OVERNIGHT...BUT SINCE THE CLOUD DECK WILL BE THIN AND WINDS WILL BE LIGHT THERE WAS ENOUGH CONFIDENCE TO EXTEND THE ADVISORY FOR AREAS OF FROST LATE TONIGHT. MIN TEMPS WILL RANGE FROM THE UPPER 20S TO LOWER 30S IN THE HIGHLANDS...TO THE MIDDLE 30S ACROSS THE SHENANDOAH VALLEY INTO THE NORTHERN AND WESTERN SUBURBS OF WASHINGTON AND BALTIMORE...TO THE MIDDLE 40S IN DOWNTOWN WASHINGTON AND BALTIMORE.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... A ONE-DAY REPRIEVE FROM THE FALL-LIKE CONDITIONS AS THE SFC HIGH ROLLING ACROSS THE CAROLINAS MAKES AN EXIT OFF THE COAST AND BRINGS IN RETURN SLY FLOW. THIS WIND REGIME WILL ALLOW FOR A MINOR WARM-UP RELATIVE TO TODAY`S CONDITIONS. AS WINDS SWITCH OUT OF THE SOUTH FOR MUCH OF THE DAY...A FAST-MOVING CLIPPER-LIKE FEATURE WILL DIVE DOWN TOWARD THE AREA FROM N OF THE GREAT LAKES. AS THE APEX OF THE UPPER SHORTWAVE REACH NRN NY MON EVE...THE SYSTEM AS A WHOLE WILL DECELERATE AND BEGIN TO CUT-OFF FROM THE MAIN UPPER JET STREAM. MOISTURE WILL RETURNS FROM THE TOP-DOWN AS THE SHORTWAVE APPROACHES. THICKER MID-UPPER LEVEL CLOUD DECKS WILL ARRIVE LATE MON AFTN/EVE ON THE ERN FRINGE OF THE INCOMING UPPER WAVE. FALLING PRECIP WILL HAVE A SIZABLE AMOUNT OF DRY AIR TO OVERCOME BEFORE REACHING THE SFC...BUT THIS WILL BECOME MORE PROBABLE FROM WEST TO EAST DURING THE LATE NIGHT HRS. INCREASE POPS FOR THE CNTRL APLCNS LATE MON AND KEPT A LOW CHANCE FURTHER EAST TO THE BLUE RIDGE. THE SFC TROUGH CROSSES THE CWA MONDAY NIGHT. THE LOW CROSSES THE CWA TUESDAY NIGHT. LOW CHANCES FOR LIGHT RAIN ACROSS THE CWA AS DOWNSLOPING FLOW WILL GREATLY LIMIT THE COVERAGE OF RAIN. TEMPERATURES NEAR NORMAL WITH DOWNSLOPING FLOW COUNTERACTING CLOUD COVER FROM KEEPING TEMPERATURES TOO LOW. && .LONG TERM /TUESDAY THROUGH SUNDAY/... AN UPPER LEVEL TROUGH WILL DIG ACROSS THE EASTERN UNITED STATES THROUGH THE FIRST HALF OF THE WORKWEEK. LOW PRESSURE ASSOCIATED WITH THIS TROUGH WILL JUMP SOUTHWARD FROM OVER THE GREAT LAKES TO THE MID-ATLANTIC THROUGH THE FIRST PART OF THE WORKWEEK AS HIGH PRESSURE MOVES OFFSHORE. THE LOW WILL LOOSE SOME OF ITS ORGANIZATION...LIKELY DUE TO THE PASSAGE OVER THE MOUNTAINS...BUT POPS WILL ENTER THE HIGH END CHANCE RANGE BEGINNING TUESDAY. PRECIP TYPE SHOULD MOSTLY BE LIGHT RAIN WITH LIMITED INSTABILITY. THE UPPER LEVEL LOW WILL OCCLUDE FROM THE BACKGROUND WESTERLIES AS THE ASSOCIATED SURFACE LOW DEEPENS OFF OF THE NORTHEAST COAST THROUGH THE DAY WEDNESDAY. OPERATIONAL EURO AND GFS ARE IN PRETTY GOOD AGREEMENT IN THE HIGHEST QPF ASSOCIATED WITH THIS SYSTEM BEING IN THE SOUTHEASTERN QUADRANT OF THE LOW WELL OFF OF THE COAST...BUT LIGHT PRECIPITATION COULD CONTINUE LOCALLY THROUGH WEDNESDAY AFTERNOON. COOL AND BREEZY NORTHERLY FLOW WILL FILL IN AS THE LOW SLOWLY MOVES UP THE COAST THROUGH THE SECOND HALF OF THE WORKWEEK. THIS WILL LEAD TO CLEARING SKIES AND TEMPS 5 TO 10 DEGREES BELOW NORMAL THURSDAY AND FRIDAY. HIGH PRESSURE WILL SETTLE OVERHEAD FOR THE WEEKEND ALLOWING TEMPS TO BEGIN TO SLOWLY REBOUND TOWARD NORMAL. && .AVIATION /01Z MONDAY THROUGH FRIDAY/...
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WINDS WILL REMAIN LIGHT TONIGHT BEFORE TURNING TO THE SOUTH MONDAY WITH GUSTS AROUND 15 TO 20 KNOTS DURING THE LATE MORNING AND AFTERNOON HOURS. WINDS WILL DIMINISH MONDAY NIGHT. VFR CONDITIONS ARE EXPECTED THROUGH MONDAY EVENING. PATCHY BR IS POSSIBLE OVERNIGHT MONDAY. CONFIDENCE IS LOW IN THE OCCURRENCE OF AVIATION HAZARDS THROUGH THE LONG TERM PERIOD.
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&& .MARINE...
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WINDS WILL CONTINUE TO DIMINISH OVER THE WATERS TONIGHT AS HIGH PRESSURE BUILDS OVERHEAD. THE SMALL CRAFT ADVISORY HAS BEEN CANCELLED. WINDS WILL SHIFT TO THE SOUTH MONDAY AND GUSTS MAY APPROACH SCA CRITERIA DURING THE LATE MORNING AND AFTERNOON HOURS. HAVE CAPPED GUSTS AT 15 KNOTS FOR NOW DUE TO THE RELATIVELY COOLER WATERS. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE CHESAPEAKE BAY AND LOWER TIDAL POTOMAC IN GUSTY NORTHERLY WINDS AS LOW PRESSURE MOVES UP THE NORTHEAST COAST BEGINNING WEDNESDAY MORNING AND CONTINUING THROUGH FRIDAY NIGHT.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR MDZ003>007-009- 010-501-502. VA...FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR VAZ025>031- 036>040-042-050>053-501-502. FREEZE WARNING FROM 2 AM TO 9 AM EDT MONDAY FOR VAZ503-504. WV...FROST ADVISORY FROM 2 AM TO 9 AM EDT MONDAY FOR WVZ050>053-055- 502>504. FREEZE WARNING FROM 2 AM TO 9 AM EDT MONDAY FOR WVZ501-505-506. MARINE...NONE.
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&& $$ SYNOPSIS...GMS NEAR TERM...BJL SHORT TERM...GMS LONG TERM...BJL/CEB AVIATION...BJL/GMS/CEB MARINE...BJL/GMS/CEB

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