Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 182016 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 316 PM EST THU DEC 18 2014 .SYNOPSIS...
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AN UPPER-LEVEL DISTURBANCE WILL PASS THROUGH THE REGION TONIGHT AND HIGH PRESSURE WILL BUILD OVERHEAD FRIDAY THROUGH FRIDAY NIGHT. LOW PRESSURE WILL TRACK SOUTH OF THE AREA SATURDAY THROUGH SUNDAY. A SECONDARY LOW IS EXPECTED TO MOVE UP FROM THE SOUTHEAST COAST EARLY NEXT WEEK. A LARGE AREA OF LOW PRESSURE LOOKS TO DEVELOP IN THE OHIO VALLEY DURING THE MIDDLE OF NEXT WEEK.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SFC HIGH PRESSURE WILL CONTINUE TO BUILD ACROSS THE GREAT LAKES TONIGHT WHILE LOW PRESSURE PULLS AWAY FROM THE CANADIAN MARITIMES. STRATOCUMULUS HAS BEEN STUBBORN THIS AFTERNOON...BUT APPEARS THEY WILL GRADUALLY ERODE FROM THE SOUTH THIS AFTERNOON. MAY HANG ON ALONG THE MD/PA BORDER INTO THE NIGHT. EVEN THOUGH PRECIP ASSOCIATED WITH A SHORTWAVE APPROACHING FROM THE LOWER OHIO VALLEY HAS SHOWN A WEAKENING TREND WHILE MOVING INTO A DRIER AIRMASS...THOUGHT IT WAS WORTHWHILE TO AT LEAST MENTION A SLIGHT CHANCE OF SNOW SHOWERS IN THE MOST FAVORED UPSLOPE AREAS TONIGHT. OTHERWISE...A BLANKET OF MID LEVEL CLOUDS WILL SPREAD IN OVERNIGHT. THIS WILL KEEP TEMPERATURES FROM PLUMMETING TO THE DEW POINTS...BUT LOWS WILL STILL DIP BELOW FREEZING IN MOST LOCATIONS.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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HIGH PRESSURE WILL BE IN CONTROL FOR FRIDAY AND FRIDAY NIGHT...LEADING TO TRANQUIL WEATHER AND LESS GUSTY WINDS. PERHAPS SOME PASSING CLOUDS BUT EVEN OVERNIGHT WITH THE MORE SUPPRESSED SOUTHERN STREAM SYSTEM...MOST OF THE CWA MAY ONLY SEE CIRRUS. NOT MUCH TEMPERATURE ADVECTION...HIGHS PERHAPS A TICK WARMER BUT STILL IN THE 40S...WITH OVERNIGHT LOWS BELOW FREEZING. SURFACE HIGH PRESSURE WILL BUILD OVER NEW ENGLAND AND THE RIDGE AXIS WILL EXTEND SOUTH INTO THE MID-ATLANTIC SATURDAY THROUGH SATURDAY NIGHT. THIS WILL ALLOW FOR SEASONABLY CHILLY CONDITIONS DURING THIS TIME. A COUPLE SHORTWAVES...ONE IN THE NORTHERN STREAM OF THE JET AND ONE IN THE SOUTHERN STREAM OF THE JET WILL PASS THROUGH OUR REGION SATURDAY AFTERNOON AND NIGHT. THESE SYSTEMS WILL NOT PHASE SO THE NORTHERN STREAM SHORTWAVE WILL REMAIN TO OUR NORTH AND THE SOUTHERN STREAM SHORTWAVE WILL REMAIN TO OUR SOUTH. MOST OF THE MOISTURE WILL REMAIN TO OUR SOUTH WITH THE SOUTHERN STREAM SYSTEM AS WELL. THEREFORE...MOST AREAS ARE EXPECTED TO REMAIN DRY DURING THIS TIME. HOWEVER...LIGHT PRECIPITATION MAY BRUSH PORTIONS OF THE POTOMAC HIGHLANDS AND CENTRAL VIRGINIA SATURDAY INTO SATURDAY NIGHT. THERE WILL BE ENOUGH COLD AIR FOR SNOW IF PRECIPITATION OCCURS...BUT LITTLE OR NO SNOW ACCUMULATION IS EXPECTED WITH MOST OF THE MOISTURE REMAINING TO THE SOUTH. MAX TEMPS SATURDAY WILL RANGE FROM THE 30S IN THE MOUNTAINS TO THE LOWER AND MIDDLE 40S ACROSS MOST OTHER LOCATIONS. MIN TEMPS SATURDAY NIGHT WILL BE IN THE MID TO UPPER 20S ACROSS MOST LOCATIONS...BUT LOWER AND MIDDLE 30S IN DOWNTOWN WASHINGTON AND BALTIMORE.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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UPPER LEVEL CUT-OFF LOW CENTERED OVER THE UPPER MISSISSIPPI VALLEY SUNDAY WILL SLOWLY DRIFT TO THE EAST AND FILL BY WEDNESDAY NIGHT. A SHORTWAVE MOVING THROUGH THE PATTERN WILL SUPPORT DEVELOPMENT OF A SURFACE LOW OVER EASTERN NORTH CAROLINA AND VIRGINIA WEDNESDAY. SURFACE LOW WILL MOVE ON TO NEW ENGLAND BY WEDNESDAY NIGHT. MOISTURE WILL INCREASE OVER MID ATLANTIC REGION WILL INCREASE ON SOUTHWEST WINDS DURING EARLY HALF OF PERIOD. MARGINAL 1000-500 MB THICKNESS VALUES AND AIR TEMPERATURES AROUND FREEZING MAY SUPPORT SNOW...OR WINTRY MIX. MORE MOISTURE WILL FOLLOW AT MID WEEK AHEAD OF LOW APPROACHING FROM THE MID WEST. TEMPERATURES SHOULD STAY HIGH ENOUGH THAT PRECIPITATION SHOULD BE RAIN.
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&& .AVIATION /19Z THURSDAY THROUGH TUESDAY/...
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BKN CIGS NEAR 4KFT SHOULD ERODE BY LATE AFTERNOON BUT GIVE WAY TO INCREASING MID LEVEL CIGS OVERNIGHT. HOWEVER VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. WINDS REMAIN OUT OF THE NW BUT BECOME LESS GUSTY TONIGHT AND FRIDAY. VFR CONDITIONS ARE EXPECTED ACROSS MOST OF THE TERMINALS SATURDAY THROUGH SATURDAY NIGHT. A PERIOD OF LIGHT SNOW OR RAIN MAY IMPACT KCHO. SUBVFR CONDITIONS ARE POSSIBLE IF ANY PRECIPITATION DEVELOPS. HIGH PRESSURE WILL BUILD OVER THE TERMINALS SUNDAY...BUT LOW PRESSURE MAY IMPACT THE AREA TUESDAY AND WEDNESDAY WITH PRECIPITATION AND SUBVFR CONDITIONS.
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&& .MARINE...
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HIGH PRESSURE AFFECTS THE WATERS THROUGH FRIDAY NIGHT. EXTENDED BOTH SEGMENTS OF THE SCA INTO THIS EVENING AS NOT SURE THE GUST WILL DECREASE TOO QUICKLY. WINDS INCREASE AGAIN FOR THE DAYTIME OF FRIDAY...WITH A SCA GOING INTO EFFECT FOR MOST OF THE WATERS. WINDS WILL DIMINISH FRIDAY EVENING. HIGH PRESSURE WILL REMAIN OVER THE WATERS SATURDAY THROUGH SUNDAY. LOW PRESSURE WILL IMPACT THE WATERS EARLY NEXT WEEK.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EST THIS EVENING FOR ANZ530>534-537>543. SMALL CRAFT ADVISORY FROM 7 AM TO 3 PM EST FRIDAY FOR ANZ531>534-537>543. SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR ANZ535- 536.
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&& $$ SYNOPSIS...BJL NEAR TERM...ADS SHORT TERM...BJL/ADS LONG TERM...BJL/CEM AVIATION...BJL/ADS MARINE...BJL/ADS

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