Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 140133 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 833 PM EST SAT DEC 13 2014 .SYNOPSIS... HIGH PRESSURE GRADUALLY BUILDS INTO THE AREA THROUGH THE WEEKEND AND WILL BE OVERHEAD BY MONDAY. THE HIGH SLIDES OFFSHORE MONDAY NIGHT AS LOW PRESSURE LIFTING ACROSS THE GREAT LAKES REGION BRINGS A COLD FRONT THROUGH THE REGION TUESDAY. HIGH PRESSURE RETURNS FOR THE SECOND HALF OF NEXT WORKWEEK. && .NEAR TERM /THROUGH SUNDAY/...
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MAIN CONCERN FOR THE OVERNIGHT WILL BE THE UPSLOPE WIND COMPONENT MAINTAINING LOW LEVEL MOISTURE SUFFICIENT FOR DRIZZLE AND FOG OVER THE WESTERN SLOPES OF THE POTOMAC HIGHLANDS. ALREADY HAVE CLOUDS AND SOME FOG IN PLACE...AND DRIZZLE OR LIGHT RAIN IS EXPECTED TO FOLLOW SUIT OVERNIGHT. WITH TEMPERATURES BELOW FREEZING...THIS WOULD RESULT IN LIGHT ICING AND FREEZING RAIN ADVISORY IS IN EFFECT THROUGH SUNDAY MORNING. EAST OF HERE...EXPECT MAINLY MID-HIGH CLOUDS OVERNIGHT ALTHOUGH IT/S POSSIBLE SOME STRATUS TRY TO SNEAK INTO THE REMAINDER OF WESTERN/NORTHERN MARYLAND BY SUNDAY MORNING. UPPER RIDGE WILL BUILD A BIT FURTHER EAST ON SUNDAY AND NORTHWEST FLOW WILL PERSIST ACROSS THE REGION. AFTERNOON HIGH TEMPERATURES ARE EXPECTED TO REACH THE 40S TO LOWER 50S ONCE AGAIN...EXCEPT 30S OVER THE WESTERN FIVE.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... THE SHORT TERM PERIOD WILL SIGNAL THE TRANSITION FROM THE FAIR CONDITIONS THAT MOST OF THE AREA WILL EXPERIENCE THIS WEEKEND TO THE WETTER MIDDLE OF THE WEEK. RIDGING ALOFT AND HIGH PRESSURE AT THE SURFACE WILL KEEP THE INVERSION AT THE TOP OF THE PBL IN PLACE THROUGH MONDAY NIGHT. THIS...COMBINE WITH LIGHT WEST TO NORTHWESTERLY WINDS IN THE LOWER LEVELS WILL CONTINUE OCCASIONAL DRIZZLE ALONG THE ALLEGHENY FRONT THROUGH SUNDAY NIGHT. SOME PORTIONS OF THE POTOMAC HIGHLANDS...MAINLY THE HIGHEST ELEVATIONS...SHOULD DIP BELOW FREEZING LATE SUNDAY NIGHT AND SOME FREEZING DRIZZLE IS POSSIBLE. ELSEWHERE...CLOUD COVER SHOULD BE SPARSE AS HIGH PRESSURE MOVES OVERHEAD SUNDAY NIGHT AND MONDAY. HIGHS SHOULD BE ABLE TO GET UP AROUND 50 THANKS TO THE SUNSHINE AND LIGHT WINDS...THROUGH THERE IS LITTLE WAA TO SPEAK OF...SO TEMPS SHOULDNT GET TOO MUCH ABOVE 50. THE OMEGA HIGH WILL WEAKEN AND SHIFT OFFSHORE MONDAY NIGHT AND UPPER LEVEL HEIGHT FALLS WILL BEGIN. A COLD FRONT ASSOCIATED WITH SURFACE LOW PRESSURE LIFTING FROM THE SOUTHERN GREAT PLAINS ACROSS THE GREAT LAKES WILL APPROACH THE AREA LATE MONDAY NIGHT INTO EARLY TUESDAY MORNING. WEAK PREFRONTAL WAA WILL BEGIN MONDAY NIGHT...ENSURING THAT TEMPS STAY ABOVE FREEZING AS THE PRECIP APPROACHES...WITH LOWS MONDAY NIGHT IN THE MID-TO-UPPER 30S ALL PRECIP FROM THE FRONT SHOULD FALL AS RAIN. && .LONG TERM /TUESDAY THROUGH SATURDAY/... THERE IS A CHANCE FOR RAIN SHOWERS TUESDAY AS A SURFACE COLD FRONT PUSHES ACROSS THE REGION...ALONG WITH ITS ASSOCIATED UPPER LEVEL DISTURBANCE. HIGH PRESSURE OVER THE TENNESSEE VALLEY WILL BUILD BEHIND THE TROUGH OF LOW PRESSURE AND SURFACE FRONT TUESDAY NIGHT. ANY PRECIPITATION TUESDAY NIGHT SHOULD BE MAINLY IN THE POTOMAC HIGHLANDS IN THE FORM OF RAIN OR SNOW SHOWERS DUE TO AN UPSLOPE COMPONENT OF THE WIND. ANOTHER UPPER LEVEL DISTURBANCE WILL FOLLOW THE FRONT WEDNESDAY...CUTTING BEHIND THE BUILDING RIDGE OF HIGH PRESSURE AND ONLY BRINGING ANOTHER CHANCE FOR SOME HIGHER ELEVATION SNOW SHOWERS TO THE POTOMAC HIGHLANDS. OTHERWISE...HIGH PRESSURE WILL REINFORCE ITSELF AND BRING DRY CONDITIONS TO THE MID ATLANTIC REGION WEDNESDAY THROUGH THURSDAY. A WEAK PIECE OF ENERGY WILL DROP SOUTHEASTWARD FROM THE GREAT LAKES INTO THE MID ATLANTIC THURSDAY NIGHT. IF ENOUGH MOISTURE IS PRESENT AND TEMPERATURES ARE CHILLY ENOUGH...THERE COULD BE A SLIGHT CHANCE OF A LIGHT WINTRY MIX...MAINLY IN THE POTOMAC HIGHLANDS OR VIRGINIA PIEDMONT AND CENTRAL SHENANDOAH VALLEY. FOR NOW...WE HAVE LEFT THE FORECAST DRY. AS HIGH PRESSURE SLIDES TO THE DELMARVA PENINSULA AND EAST COAST FRIDAY AND FRIDAY NIGHT...AN UPPER LEVEL DISTURBANCE WILL RIDE ALONG THE OHIO VALLEY. THERE IS A CHANCE OF ENCOUNTERING A WINTRY MIX OF SNOW...SLEET...AND FREEZING RAIN ACROSS THE REGION FRIDAY NIGHT AS THE UPPER LEVEL DISTURBANCE APPROACHES THE EASTERN OHIO VALLEY AND SPINE OF THE APPALACHIAN MOUNTAINS. OF COURSE...THERE IS HIGH UNCERTAINTY IN THE TRACK OF THE UPPER LEVEL DISTURBANCE AND IN THE AMOUNT OF COLD AIR IN PLACE TO PRODUCE WINTRY PRECIPITATION. BOTH THE EUROPEAN AND GFS MODELS ARE LEANING TOWARD THE SOLUTION OF THE UPPER LEVEL DISTURBANCE AND WINTRY MIX. TIMING IS A BIG FACTOR WITHIN THAT LEVEL OF UNCERTAINTY. WITH THE POSSIBILITY OF POTENT UPPER LEVEL STORM SYSTEM FRIDAY INTO FRIDAY NIGHT AND HIGH LEVELS OF UNCERTAINTY IN THE TIMING OF THE DISTURBANCE...WE LEFT A CHANCE OF RAIN AND SNOW SHOWERS ACROSS THE CWA FOR SATURDAY. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/...
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VFR CONDITIONS EXPECTED AT ALL TERMINAL SITES INTO SUNDAY MORNING. LEANED TOWARD NAM IN ALLOWING SOME MVFR CLOUDS FOR THE AFTERNOON. NORTHWEST WINDS WILL BECOME BREEZY ON SUNDAY WITH SPEEDS GENERALLY IN THE 10-15KT RANGE WITH GUSTS UP TO 20KTS POSSIBLE. MVFR OR IFR CONDITIONS ARE POSSIBLE IN ANY RAIN SHOWERS TUESDAY. VFR CONDITIONS RETURN TUESDAY NIGHT. WINDS SOUTHERLY LESS THAN 5 KNOTS BECOMING WESTERLY AT 5 TO 10 KNOTS LATE TUESDAY INTO TUESDAY NIGHT.
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&& .MARINE...
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WINDS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA TONIGHT. SCA CONDITIONS THEN ARE LIKELY SUNDAY MORNING INTO THE AFTERNOON WITH NORTHWEST WINDS GUSTING UP TO 20 KT. SUB-ADVISORY WIND CONDITIONS SHOULD RETURN SUNDAY NIGHT AND REMAIN THROUGH TUESDAY. SMALL CRAFT ADVISORIES MAY BE NEEDED WEDNESDAY WITH INCREASING WEST TO NORTHWEST WINDS. WINDS COULD GUST TO 25 KNOTS.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...FREEZING RAIN ADVISORY UNTIL 10 AM EST SUNDAY FOR MDZ501. VA...FREEZING RAIN ADVISORY UNTIL 10 AM EST SUNDAY FOR VAZ503. WV...FREEZING RAIN ADVISORY UNTIL 10 AM EST SUNDAY FOR WVZ501-503- 505. MARINE...SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM EST SUNDAY FOR ANZ530>543.
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&& $$ SYNOPSIS...KRW NEAR TERM...BPP/KRW SHORT TERM...CEB LONG TERM...KLW AVIATION...BPP/KRW/CEB/KLW MARINE...BPP/KRW/CEB/KLW

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