Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141850 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 150 PM EST SUN DEC 14 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVERHEAD THROUGH TONIGHT BEFORE SLOWLY MOVING TO OUR EAST MONDAY THROUGH MONDAY NIGHT. A COLD FRONT WILL PASS THROUGH THE AREA LATER TUESDAY INTO TUESDAY NIGHT AND HIGH PRESSURE WILL RETURN FOR THE WEDNESDAY THROUGH FRIDAY. LOW PRESSURE MAY IMPACT THE AREA NEXT WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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SURFACE HIGH PRESSURE REMAINS ACROSS WEST VIRGINIA...EASTERN KY/TN AND FURTHER SOUTH THIS AFTERNOON. NW FLOW AROUND THE HIGH WILL CONTINUE THROUGH THE AFTERNOON. BOUNDARY LAYER GOES UP TO ABOUT 900MB...WITH A STRONG INVERSION RIGHT ABOVE IT. LOW LEVEL MOISTURE TRAPPED BELOW THE INVERSION IS KEEPING A STRATUS DECK OVER ALL OF MD...THE ERN WV PANHANDLE AND NORTHERN VA. UNDERNEATH THE CLOUDS...TEMPS ARE IN THE 40S WITH A FEW SPOTS IN THE LOW 50S. FURTHER SOUTH...CLEAR SKIES HAVE ALLOWED TEMPS TO REACH THE MID 50S. THERES ALSO PLENTY OF WINDS BELOW THE INVERSION FOR GUSTS UP TO 20-25 KTS ACROSS THE NORTHERN HALF OF THE FORECAST AREA. THE HIGH WILL GRADUALLY BUILD INTO THE WESTERN HALF OF THE FORECAST AREA TONIGHT. FORECAST SOUNDINGS INDICATE CLOUDS ALREADY IN PLACE WILL PERSIST BENEATH THE INVERSION OVERNIGHT. RADIATIONAL COOLING WILL BE MORE EFFECTIVE FURTHER SOUTH...WHERE LOW TEMPS WILL DROP TO NEAR FREEZING. SLIGHTLY WARMER UNDER THE CLOUDS OVER THE NORTHERN HALF OF THE CWA...WHERE LOWS ARE EXPECTED TO BE IN THE MID TO UPPER 30S. FOR LOCATIONS ALONG AND WEST OF THE ALLEGHENY FRONT...THERE IS SOME POTENTIAL FOR FREEZING DRIZZLE TONIGHT. BOUNDARY LAYER WILL BE A LITTLE BIT DRYER HOWEVER...AND LOW TEMPS WILL BE A FEW DEGREES WARMER THAN LAST NIGHT. NOT ENOUGH CONFIDENCE TO ISSUE A FREEZING RAIN ADVISORY TONIGHT.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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HIGH PRESSURE BOTH AT THE SURFACE AND ALOFT WILL BUILD OVERHEAD MONDAY BEFORE SLOWLY SHIFTING TO THE EAST MONDAY AFTERNOON. DRY AND MILD CONDITIONS ARE EXPECTED ALONG WITH SUNSHINE. MAX TEMPS WILL RANGE FROM THE MID TO UPPER 40S ACROSS MARYLAND AND NRN VIRGINIA TO THE LOWER AND MIDDLE 50S IN CENTRAL VIRGINIA. ELONGATED HIGH PRESSURE ALONG THE EASTERN US PUSHES EAST MONDAY NIGHT AHEAD OF APPROACHING LOW PRESSURE SYSTEM PASSING THROUGH THE GREAT LAKES. RIDGE AXIS CROSSES THE REGION LATE MONDAY AS UPPER LVL TROUGH DIPS SOUTH AND PIVOTS EAST. BEGAN MONDAY NIGHT WITH DRY WX...THEN INTRODUCED POPS FOR THE SECOND HALF OF THE NIGHT WITH OVERRIDING PCPN AS A WARM FRONT LIFTS NORTH. BUFKIT SOUNDINGS INDICATING FAIRLY DRY AIR ALOFT...SO COULD AT FIRST SEE A BRIEF PERIOD OF DZ THEN TRANSITIONING TO SCT RAIN SHOWERS WITH A PASSING SHORTWAVE BY 12Z TUES. COLD FRONT SWINGS THROUGH LATE IN THE AREA...WITH INCREASING COVERAGE OF SHOWERS OUT AHEAD OF THE FRONT. 00Z MODEL GUIDANCE GENERALLY AGREEING ON THE COLD FRONT PUSHING OFFSHORE BY 06Z WED. PCPN WILL TAPER OFF OVER EASTERN AREAS...BUT EXPECTING UPSLOPE SNOW SHOWERS AS A WESTERLY FLOW SETS UP IN THE WAKE OF THE FRONT.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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AN UPPER LEVEL DISTURBANCE OVER THE GREAT LAKES WILL SHIFT TO THE EAST WEDNESDAY AND WEDNESDAY NIGHT BEFORE PIVOTING ACROSS THE MID ATLANTIC THURSDAY. MUCH OF THE REGION SHOULD BE DRY WITH EXCEPTION TO A CHANCE FOR SNOW SHOWERS IN THE HIGHER ELEVATIONS OF THE POTOMAC HIGHLANDS WEDNESDAY AND WEDNESDAY NIGHT. HIGH PRESSURE WILL BUILD LATE THURSDAY THROUGH FRIDAY. AS HIGH PRESSURE SLIDES TO THE DELMARVA PENINSULA AND EAST COAST LATE FRIDAY AND FRIDAY NIGHT...AN UPPER LEVEL DISTURBANCE WILL MOVE EAST ACROSS THE LOWER GREAT LAKES AND OHIO VALLEY. ENERGY AHEAD OF THE MAIN UPPER LEVEL LOW WILL COMBINE WITH SOME INCREASING MID LEVEL MOISTURE FRIDAY NIGHT INTO SATURDAY TO BRING A CHANCE OF A MIX OF LIGHT RAIN OR LIGHT SNOW. THERE ARE STILL SOME UNCERTAINTIES IN THE TRACK...INTENSITY...AND TIMING OF THE MAIN UPPER LEVEL STORM. COMPUTER MODELS ARE INDICATING THAT A SURFACE LOW COULD FORM NEAR THE COAST OF NORTH CAROLINA IN AFFILIATION WITH THIS UPPER LEVEL DISTURBANCE SOMETIME SATURDAY. SHOULD THIS COASTAL LOW DEVELOP...WE LEFT A CHANCE FOR SOME LIGHT SNOW ACROSS THE CWA FOR SATURDAY NIGHT. BY SUNDAY...THE MAIN DISTURBANCE WILL BE ACROSS NEW ENGLAND WITH A SURFACE LOW MOVING GRADUALLY OUT TO SEA. HIGH PRESSURE WILL WORK ITS WAY INTO THE REGION...RESULTING IN DRIER CONDITIONS. SOME UPSLOPE RAIN OR SNOW SHOWERS ARE POSSIBLE IN THE POTOMAC HIGHLANDS WITH A CHANCE OF SOME LINGERING RAIN OR SNOW SHOWERS IN THE NORTH AND EAST WITH RESPECT TO THE DEPARTING LOW PRESSURE.
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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VFR CONDITIONS THROUGH TONIGHT. BALTIMORE/WASHINGTON TERMINALS WILL CONTINUE TO BE BENEATH A STRATUS CLOUD DECK WITH CIGS AROUND 035-040. SOME CHANCE THAT CIGS MAY DROP TO MVFR TONIGHT...BUT NOT ENOUGH CONFIDENCE TO INCLUDE IN TAFS. WINDS THIS AFTERNOON HAVE BEEN GUSTY FROM THE NW AT KIAD/KMRB...UP TO 25KTS AT TIMES. POTENTIAL STILL EXISTS FOR SOME GUSTS AT KDCA/KBWI...BUT MAY BE SPORADIC. THE WINDS WILL DIMINISH AROUND SUNSET THIS EVENING....WITH 10KT OR LESS FROM THE NW OVERNIGHT. VFR CONDITIONS ARE EXPECTED MONDAY WITH HIGH PRESSURE OVERHEAD. GENERALLY VFR CONDITIONS MONDAY NIGHT...WITH DECREASING CONDITIONS AS PCPN MOVES IN. SUB-VFR CONDITIONS LIKELY WITH ANY PCPN TUES. PCPN EXPECTED TO REMAIN RAIN SHOWERS AT THIS TIME. VFR CONDITIONS WEDNESDAY AND WEDNESDAY NIGHT. WINDS WEST TO NORTHWEST 10 TO 20 KNOTS WITH HIGHER GUSTS BUT DIMINISHING WEDNESDAY NIGHT. VFR CONDITIONS THURSDAY. WINDS NORTHWEST AROUND 10 KNOTS.
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&& .MARINE...
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CANCELLED SMALL CRAFT ADVISORY FOR THE NORTHERN CHESAPEAKE BAY AND SURROUNDING WATERS...INCLUDING BALTIMORE HARBOR. SMALL CRAFT ADVISORY REMAINS EFFECT FOR THE REST OF THE WATERS THIS AFTERNOON. GUSTS HAVE BEEN SLOW TO DEVELOP DUE TO CLOUD COVER AND COOL WATER TEMPS...BUT GIVEN UPWARD TREND IN GUSTS OVER THE POTOMAC RIVER AND THE LOWER HALF OF THE BAY...WILL KEEP THE SCA GOING FOR NOW. WITH NW FLOW ALOFT...MODELS INDICATE A MODEST SURGE OF COOLER AIR ALOFT AFTER SUNSET WHICH MAY ALSO KEEP GUSTS GOING INTO THE NIGHT...SO WILL KEEP SCA IN EFFECT FOR ALL ZONES EXCEPT THE NORTHERN TIDAL POTOMAC AND CHESAPEAKE BAY NORTH OF SANDY POINT TONIGHT. SUB-SCA CONDITIONS INITIALLY MONDAY NIGHT. WINDS INCREASE BY TUESDAY MORNING AHEAD OF AN APPROACHING COLD FRONT BUT GUSTS ARE EXPECTED TO REMAIN LESS THAN 18 KTS THRU TUES NIGHT. A BRIEF LULL TUES EVENING WITH THE PASSAGE OF THE FRONT...THEN GUSTS INCREASE AGAIN INTO THE 20S AS WINDS SHIFT TO THE WEST BEHIND THE FRONT. SMALL CRAFT ADVISORIES MAY BE NEEDED WEDNESDAY WITH GUSTS TO 20 KNOTS. NO MARINE HAZARDS WEDNESDAY NIGHT AND THURSDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST MONDAY FOR ANZ531>534-537- 539>541-543. SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ530- 535-536-538-542. && $$

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