Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 190714 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 314 AM EDT SUN OCT 19 2014 .SYNOPSIS... AN UPPER TROUGH AXIS WILL CLEAR THE AREA LATER TONIGHT...WITH CANADIAN HIGH PRESSURE BUILDING TROUGH MONDAY. A SLOW MOVING CUT OFF UPPER LEVEL LOW PRESSURE SYSTEM WILL HOVER AROUND THE EAST COAST THROUGH MUCH OF NEXT WEEK. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... HIGH PRESSURE WILL BUILD INTO THE GREAT LAKES AND TENNESSEE VALLEY OVERNIGHT WHILE A COLD FRONT CONTINUES TO MOVE OFF THE COAST. A NORTHWEST FLOW IN BETWEEN THESE SYSTEMS WILL CONTINUE TO USHER IN CHILLIER AIR DURING THIS TIME. AN UPPER-LEVEL TROUGH WILL SWING THROUGH THE AREA...BRINGING SOME CLOUDS WITH IT BUT ANY PRECIPITATION WILL BE LIGHT AND CONFINED TO LOCATIONS ALONG AND WEST OF THE ALLEGHENY FRONT WHERE THERE IS AN UPSLOPE COMPONENT TO THE LOW-LEVEL FLOW. THERE MAY BE ENOUGH COLD AIR FOR A FEW FLURRIES OR SNOW SHOWERS ALONG THE RIDGE TOPS...BUT LITTLE OR NO SNOW ACCUMULATION IS EXPECTED. 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. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
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UPDATE...A FREEZE WATCH IS IN EFFECT FOR THE POTOMAC HIGHLANDS...ALLEGHENY HIGHLANDS AND PORTIONS OF THE CENTRAL SHENANDOAH VALLEY LATE SUNDAY NIGHT INTO MONDAY MORNING. PREVIOUS DISCUSSION... SFC HIGH PRESSURE CENTER ENTERS THE CWA FROM THE WEST SUNDAY AFTERNOON...MOVING OFFSHORE MONDAY MORNING. GUSTY NWLY FLOW THROUGH SUNDAY...EXPECT 30 MPH GUSTS THROUGH MUCH OF THE DAY. DOWNSLOPING FLOW WILL WARM AS IT DESCENDS WITH MORNING CLOUDS OVER THE MOUNTAIN QUICKLY DISSIPATING (ALONG WITH ANY LIGHT WINTRY MIX PRECIP WEST OF THE ALLEGHENY FRONT). MAX TEMPS GENERALLY MID TO UPR 50S AT LOWER ELEVATION. 60F POSSIBLE EAST OF THE BLUE RIDGE. SUNDAY NIGHT...HIGH PRESSURE CROSSES THE MOUNTAINS IN THE EVENING...TO THE CHESAPEAKE BAY BY SUNRISE. CLEAR...CALM...AND DRY WILL MAKE FOR AN IDEAL RADIATIONAL COOL NIGHT. MIN TEMPS AROUND FREEZING LIKELY PIEDMONT AND VALLEYS WEST OF THE BLUE RIDGE (INVERSION FOR RIDGES). COULD NEED A FROST OR FREEZE HEADLINE FOR NEARLY ALL OF THE CWA (GRIDDED GUIDANCE GENERALLY HAS A WARM BIAS FOR INTERIOR SOUTHERN MARYLAND ON CLEAR/CALM NIGHTS). LOW TO MID 40S FOR URBAN/NEAR SHORE. RETURN FLOW MONDAY AS HIGH PRESSURE MOVES OFFSHORE AND LOW PRESSURE APPROACHES FROM THE GREAT LAKES. MOISTURE RETURNS WITH RAIN CHANCES INCREASING FROM THE WEST MONDAY AFTERNOON AHEAD OF AN AMPLIFYING TROUGH. UPR TROUGH AXIS CROSSES THE CWA MONDAY NIGHT WITH LOW CHANCES FOR LIGHT RAIN ACROSS THE CWA.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... ECMWF HAS 500MB CUT-OFF LOW OVER WESTERN PA TUESDAY NIGHT WITH VORT MAX DROPPING DOWN WEST SIDE OF TROUGH. VORT MAX WILL ROUND THE BOTTOM OF THE TROUGH WEDNESDAY MORNING AND MOVE OFFSHORE BY WEDNESDAY EVENING. UPPER LEVEL LOW WILL CROSS CWA LATE TUESDAY INTO WEDNESDAY AND MOVE OFFSHORE WEDNESDAY EVENING. BROAD UPPER LEVEL LOW PRESSURE PATTERN WILL SET UP OVER CANADA AND NEW ENGLAND THROUGH THE REST OF THE PERIOD. CWA WILL BE ON THE SOUTHERN EDGE OF THE TROUGH WITH SHORTWAVE CROSSING AREA FRIDAY. ALTHOUGH ANTICIPATED PATH OF THE SURFACE LOW WILL KEEP THE STRONGEST OF ITS ASSOCIATED PRECIPITATION IN PA...OUR CWA LOOKS TO GET WET ALSO. GREATEST OPPORTUNITY FOR PRECIPITATION APPEARS TO BE TUESDAY NIGHT THROUGH THURSDAY. && .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. LOW PRESSURE APPROACHES TUESDAY WITH RAIN CHANCES INCREASING. LOW LINGERS INTO LATE IN THE WEEK.
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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 OFFSHORE. LOW PRESSURE DRIFTS OVER THE REGION THEN INTO THURSDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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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.
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&& $$ UPDATES TO SHORT TERM...AVIATION AND MARINE...KCS

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