Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171936 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 236 PM EST WED DEC 17 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO THE AREA FOR THE SECOND HALF OF THE WEEK. LOW PRESSURE IS EXPECTED TO TRACK SOUTH OF THE AREA SATURDAY NIGHT. HIGH PRESSURE SHOULD RETURN TO THE AREA FOR THE FIRST PART OF NEXT WEEK. A LARGE AREA OF LOW PRESSURE MAY DEVELOP IN THE OHIO VALLEY DURING MIDWEEK. && .NEAR TERM /TONIGHT/... HIGH PRES BLDG INTO THE AREA HAS CAUSED WNW WINDS TO GUST INTO THE L20S THIS AFTN. WINDS SHOULD ABATE THIS EVE ALLOWING FOR GOOD RAD CONDS. LOWS TNGT WL BE IN THE 25-30 RANGE ACROSS THE MAJORITY OF THE CWA...A20 IN THE HIGHLANDS...LM30S IN THE CITIES. && .SHORT TERM /THURSDAY/... NO PROBS XPCTD THU. HIGH PRES OVR THE AREA SHOULD ALLOW FOR A DAY W/ TEMPS NEAR CLIMO FOR MID DEC. HIGHS IN THE M40S FOR MOST OF THE AREA...L30S IN THE HIGHLANDS. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... VERTICALLY STACKED LOW PRESSURE WILL DRIFT TOWARD NEWFOUNDLAND THURSDAY NIGHT WHILE HIGH PRESSURE BUILDS ACROSS THE GREAT LAKES. A DAMPENING SHORTWAVE WILL APPROACH IN THE FAST SOUTHERN STREAM. DESPITE A FEW MODELS TRYING TO PRODUCE QPF IN UPSLOPE AREAS...THINK THE MOISTURE PROFILES ONLY SUPPORT AN INCREASE IN MID LEVEL CLOUDS. GOOD GUIDANCE AGREEMENT WITH TEMPERATURES RANGING FROM THE MID 20S IN THE MOUNTAINS TO LOWER 30S METROS/EAST. DRY AND TRANQUIL WEATHER FOR FRIDAY AND FRIDAY NIGHT AS THE SURFACE RIDGE BUILDS IN FULLY. HOWEVER...LOW LEVEL WINDS TAKE ON A BIT MORE OF A NW DIRECTION BEHIND THE DEPARTING TROUGH...LEADING TO WEAK CAA. HIGHS GENERALLY IN THE 40S. HIGH/MID CLOUDS INCREASE FRIDAY NIGHT AHEAD OF THE APPROACHING SOUTHERN STREAM SYSTEM. SPEED/THICKNESS OF CLOUDS MAY DETERMINE HOW LOW TEMPS DROP SINCE DEW POINTS REMAIN LOW WITH LIGHT WINDS. TRENDED TOWARD SLIGHTLY WARMER GFS/ECMWF RAW TEMPS WITH LOWS NEAR OR JUST BELOW FREEZING. MODELS CONTINUE TO TREND DOWN THE INTENSITY OF LOW PRESSURE AFFECTING THE MID-ATLANTIC OVER THE WEEKEND AND TAKE THE HIGHEST QPF OVER THE CAROLINAS. IN THE LAST 3 DAYS GUIDANCE HAS TAKEN THE SYSTEM FROM A POTENT CLOSED LOW OFF NORFOLK AT 6Z SUNDAY TO AN OPEN WAVE WITH THE MAJORITY OF ITS ENERGY WELL TO OUR SOUTH. CONFIDENCE IS GROWING IN THE CURRENT SOLUTION THAT THE MAJORITY OF PRECIP WITH THE SYSTEM...OUTSIDE OF THE HIGHER ELEVATIONS...SHOULD BE RAIN...AND QPF WILL BE FAIRLY LOW OVER THE HIGHER ELEVATIONS WHERE THE TEMPS ARE LOWEST. ANY ACCUMULATIONS SHOULD BE FOCUSED ALONG AND WEST OF THE BLUE RIDGE...THOUGH THERE IS STILL THE POSSIBILITY FOR MUCH OF THE AREA TO SEE AT LEAST A COUPLE SNOW FLAKES. PRECIP SHOULD BE OUT OF THE AREA BY MIDDAY SUNDAY. HIGH PRESSURE WILL BUILD IN SUNDAY EVENING THROUGH MIDDAY MONDAY. A LARGE UPPER LEVEL TROUGH DEVELOPING OVER THE CENTRAL CONUS MONDAY WILL KEEP WEATHER ACTIVE THROUGH THE MIDDLE OF NEXT WORKWEEK. BROAD SURFACE LOW PRESSURE PROGRESSING ACROSS THE NORTHERN GREAT PLAINS COULD HELP LIFT A STALLED COASTAL FRONT ACROSS THE AREA AS A WARM FRONT SOMETIME MONDAY NIGHT OR TUESDAY. HAVE INCLUDED LOW END CHANCE POPS IN THIS TIME FRAME TO ACCOUNT FOR THIS. A WAVE OF LOW PRESSURE MAY THEN FORM WITHIN THE COLD FRONT OF THE LARGER PARENT LOW AND MOVE THROUGH OUR AREA TUESDAY NIGHT AND WEDNESDAY BRINGING HIGH END CHANCE POPS INTO THE FORECAST. EARLY IMPRESSIONS ARE THAT P-TYPE WILL BE LARGELY ELEVATION DEPENDENT WILL LOWER ELEVATIONS MOSTLY SEEING RAIN. OVERALL CONFIDENCE IS LOW IN THE TIMING AND DETAILS OF THIS SYSTEM. TEMPS SHOULD REMAIN AROUND NORMAL THROUGH THE LONG TERM WITH THE EXCEPTION OF TUESDAY NIGHT AND WEDNESDAY/POST WARM FRONT...WHEN TEMPS WILL BE 5 TO 10 DEGREES ABOVE NORMAL. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... VFR CONDS XPCTD TNGT AND THU. THU NIGHT-FRI NIGHT...VFR CONDTIONS AND W/NW SURFACE WINDS. MVFR AND IFR CONDITIONS ARE POSSIBLE IN SHOWERS AS A WAVE OF LOW PRESSURE PASSES WELL TO OUR SOUTH SATURDAY NIGHT AND SUNDAY MORNING. && .MARINE... SOME SPOTS ON THE BAY/PTMC ARE REACHING SCA LVL GUSTS...ALTHO THIS HAS NOT BEEN WIDESPREAD TDA. WIND SHOULD BECOME LGTR OVRNGT....BUT ENOUGH PRES GRAD SHOULD EXIST THU TO AGN CREATE SCA GUSTS. WINDS WILL DIMINISH THURSDAY EVENING. NW WIND GUSTS THURSDAY AFTERNOON WILL BE MARGINAL FOR A SCA...BUT ONE MAY BE NEEDED FOR PORTIONS OF THE WATERS DEPENDING ON THE EFFICIENCY OF ATMOSPHERIC MIXING. LIGHT WINDS FRIDAY NIGHT. CONFIDENCE IS LOW IN THE OCCURRENCE OF ANY MARINE HAZARDS IN THE LONG TERM. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THURSDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY UNTIL 1 PM EST THURSDAY FOR ANZ535-536. && $$ PRODUCTS...WOODY!/ADS/CEB

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