Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190800 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 400 AM EDT SUN OCT 19 2014 .SYNOPSIS...
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AN UPPER TROUGH AXIS WILL CLEAR THE AREA THIS MORNING...WITH HIGH PRESSURE BUILDING TROUGH MONDAY. A SLOW MOVING UPPER LEVEL LOW WILL CROSS THE REGION TUESDAY AND PERSIST ALONG THE COAST THROUGH THURSDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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WATER VAPOR IMAGERY INDICATES UPPER TROUGH IS CROSSING THE FORECAST AREA EARLY THIS MORNING...WHICH IS CORROBORATED BY MID- HIGH LEVEL CLOUD DECK AND A BRIEF SURGE OF WIND GUSTS TO AROUND 15-20 KTS IN SURFACE OBSERVATIONS. BEYOND THAT...IT WILL BE A DRY PASSAGE FOR MOST OF THE REGION. BEHIND THE TROUGH...SOME UPSLOPE PRECIPITATION HAS DEVELOPED OVER WV...SO WILL CONTINUE TO INCLUDE CHANCE OF PRECIPITATION IN THE HIGHLANDS. MESONET OB AT 4000 FEET IN NEARBY TUCKER COUNTY WV INDICATES SURFACE TEMP OF 32 DEGREES...SO LIGHT SNOW IS POSSIBLE NEAR THE RIDGE TOPS. LOWER ELEVATIONS WILL SEE RAIN. LITTLE OR NO SNOW ACCUMULATION IS EXPECTED. EARLY MORNING MIN TEMPS WILL RANGE FROM THE UPPER 20S AND LOWER 30S ALONG THE RIDGE TOPS OFF THE ALLEGHENY HIGHLANDS...TO THE LOWER AND MIDDLE 40S ACROSS MOST OTHER LOCATIONS. DURING THE DAY...HIGH PRESSURE ACROSS THE OHIO VALLEY WILL BUILD EASTWARD AND APPROACH THE MID-ATLANTIC COAST. GOOD PRESSURE GRADIENT WILL CONTINUE BETWEEN THE HIGH AND A 995MB LOW PRESSURE OVER QUEBEC AND THE MARTIMES. THIS...COMBINED WITH COOLING 850MB TEMPS PROMOTING GOOD MIXING...WILL RESULT IN ANOTHER DAY OF GUSTY NW WINDS. GUSTS WILL PRIMARILY BE AROUND 20-25 MPH...THOUGH SOME 30MPH GUSTS ARE POSSIBLE. HIGH TEMPS ALONG THE I-95 CORRIDOR AND NEAR THE WATERS ARE EXPECTED TO BE IN THE LOW 60S. 50S ELSEWHERE...AND UPPER 40S AT THE RIDGE TOPS.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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HIGH PRESSURE BUILDS OVERHEAD SUNDAY NIGHT...AND THEN SHIFTS SEWD TO THE NC COAST BY EARLY MONDAY MORNING. MOSTLY CLEAR SKIES AND LIGHT WINDS WILL MAKE FOR AN IDEAL RADIATIONAL COOLING NIGHT. USED COMBINATION OF MAV/MET GUIDANCE AND SREF FOR LOW TEMPS...WHICH ARE FORECAST TO BE NEAR OR BELOW FREEZING ACROSS THE HIGHLANDS AND PORTIONS OF THE CENTRAL SHENANDOAH VALLEY. A FREEZE WATCH HAS BEEN ISSUED FOR THESE AREAS. FROST WILL ALSO BE POSSIBLE OVER A GOOD PORTION OF THE FORECAST AREA. ONLY UNCERTAINTY REGARDING FROST AND FREEZING TEMPS WILL BE THE ONSET OF WARM AIR ADVECTION AROUND THE HIGH AS IT SHIFTS TO THE SE OF US...AND POTENTIAL ARRIVAL OF MID- HIGH LEVEL CLOUDS. WILL LET LATER SHIFTS ASSESS THIS...SO WILL REFRAIN FROM A FREEZE WARNING AND FROST ADVISORIES AT THIS TIME. MONDAY...QUICK WARM UP AFTER A CHILLY NIGHT SINCE RETURN FLOW WILL BE INCREASING AS HIGH PRESSURE SHIFTS OFFSHORE. A LOW PRESSURE SYSTEM APPROACHES FROM THE GREAT LAKES MONDAY NIGHT. MOISTURE SLOWLY RETURNS WITH SLIGHT POPS FOR RAIN BY LATE MONDAY AFTERNOON IN THE POTOMAC HIGHLANDS. LOW CHANCE POPS THEN SPREAD EAST TO THE BLUE RIDGE OVERNIGHT AS THE THE PARENT LOW CROSSES BUFFALO NY. 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.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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CUT OFF LOW PRESSURE LINGERS ALONG THE MID-ATLANTIC COAST WEDNESDAY AND THURSDAY. 00Z GFS/ECMWF OPERATIONAL RUNS DEPICTING UPR LOW CROSSING THE CENTRAL MID-ATLANTIC TUESDAY NIGHT...THEN LINGERING ALONG THE MID-ATLANTIC COAST THROUGH INTO THURSDAY NIGHT. NWLY FLOW WITH PERIODIC RAIN...ALONG WITH NEAR NORMAL TEMPERATURES. COLD AIR COMES IN THE WEST SIDE...AND MOISTURE NOW LOOKS GREATER...SO SOME HIGHLAND SNOW IS POSSIBLE BOTH DAYS.
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&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/...
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VFR CONDS THROUGH THE TAF PERIOD. NW WINDS LATE TONIGHT...OCCASIONAL GUSTS TO 15KT POSSIBLE BUT NOT EXPECTED TO BE FREQUENT ENOUGH TO INCLUDE IN TAFS. GUSTS BECOME MORE FREQUENT SUNDAY MORNING THROUGH THE AFTERNOON. PREVAILING 20KT GUSTS IN TAFS...BUT SOME GUSTS TO 25KT POSSIBLE. GUSTS EASE THROUGH THE EVENING AS THE HIGH CENTER CROSSES INTO THE AREA. VFR CONTINUES THROUGH MONDAY AS THE HIGH SHIFTS OFFSHORE WITH RETURN FLOW. LOW PRESSURE APPROACHES FROM THE NORTHWEST TUESDAY WITH DOWNSLOPING FLOW LIMITING RAIN CHANCES. LOW LINGERS ALONG THE COAST THROUGH THURSDAY WITH GUSTY NORTHWEST FLOW STARTING WEDNESDAY.
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&& .MARINE...
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A SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL OF THE WATERS THROUGH SUNDAY AFTERNOON. NWLY FLOW WITH GUSTS 25 TO 30 KT EXPECTED. WINDS DIMINISH SUNDAY NIGHT AS HIGH PRESSURE CENTER CROSSES THE BAY LATE IN THE NIGHT. RETURN FLOW MONDAY AS HIGH PRESSURE MOVES OFF SHORE. LOW PRESSURE DRIFTS OVER THE REGION MONDAY NIGHT AND TUESDAY...THEN LINGERS OFF SHORE WEDNESDAY AND THURSDAY. EXTENDED SCA EXPECTED IN NWLY FLOW ON BACK SIDE OF LOW WEDNESDAY INTO FRIDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR MDZ501-502. VA...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR VAZ025>027-029-503-504. WV...FREEZE WATCH FROM LATE TONIGHT THROUGH MONDAY MORNING FOR WVZ050-055-501>506. MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ531>534- 537-539>541-543. SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530- 535-536-538-542. && $$ SYNOPSIS...KCS NEAR TERM...KCS SHORT TERM...KCS/BAJ LONG TERM...BAJ AVIATION...BAJ/KCS MARINE...BAJ/KCS

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