Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 051413 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 913 AM EST THU MAR 5 2015 .SYNOPSIS... A COLD FRONT WILL CONTINUE TO DRIFT SOUTH ACROSS THE REGION THROUGH THIS MORNING WITH PRECIPITATION CONTINUING UNTIL THIS EVENING. HIGH PRESSURE BUILDS OVERHEAD FRIDAY...THEN SETTLES OVER THE SOUTHEASTERN STATES THIS WEEKEND THROUGH THE MIDWEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 14Z...TRANSITION ZONE TO SNW RESIDES JUST N OF NAK...INVOF DCA...JUST S OF SHD. WHILE DURATION OF RAIN HAS BEEN LONGER THAN PRVSLY FCST...TRANSITION FM RA TO SNW ALSO TAKING PLACE MORE QUICKLY /IE...THERE HAS BEEN VERY LTL SLEET OBSVD/. OVER THE NEXT HOUR OR TWO...THINK THAT THE TRANSITION SHUD PROGRESS SOUTH OVER THE REST OF THE CWFA AS CAA CONTS SFC-H8. FOR SITES THAT HV SEEN SNOW...A QUICK INCH OR TWO HAS BEEN COMMON. REGIONAL RADAR SHOWS A SWATH OF PCPN ACRS THE CWFA FM SW TO NE. THIS ZONE CONNECTED TO A LONG STREAM OF MSTR...XTNDG BACK TO LA. STRONG F-GEN CNVGNC RESIDES W/IN THIS ZONE...WHICH WUD ENHANCE SNOW RATES. THERES ALSO A PERIOD OF GOOD DENDRITIC SNOW GROWTH WITHIN APPROX THE SAME CORRIDOR. BTTM LINE...ONCE SNOW STARTS... WL HV A PD OF MDT-LCLLY HEAVY SNOWFALL W/ RATES UP TO AN INCH/HR FOR SVRL HRS. FOCUS PERIOD WL BE THE MIDDLE OF THE DAY-- A PINCH ERLR TO THE NW AND LATER SE. SNOWFALL TTLS HV BEEN REFINED SLGTLY...LWR FOR PTMC HIGHLANDS AND HIER W/IN ZONE WHERE BEST INGREDIENTS RESIDE. ALSO TOUCHED UP TEMP GRIDS. TEMPS WL BE DROPPING THRUT THE DAY...BUT THE SHARPER DROP WL TAKE PLACE JUST AFTER TRANSITION TO SNOW. THE SNOW WILL QUICKLY WIND DOWN DURING THE MID-LATE AFTERNOON HOURS. BY 6 PM THE SNOW MAY BE LIMITED TO PORTIONS OF SRN MD. SKIES MAY ACTUALLY CLEAR FAIRLY QUICKLY OVERNIGHT AS THE DRY ARCTIC AIRMASS PUSHES IN. SINGLE DIGIT LOWS WILL BE COMMON TONIGHT...WITH TEENS EAST OF I-95 AND POSSIBLY BELOW ZERO IN THE MOUNTAINS. WIND CHILL ADVISORIES MAY BE NEEDED IN THE POTOMAC HIGHLANDS FOR READINGS BELOW -10F. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... HIGH PRESSURE CENTERS OVERHEAD FRIDAY WITH SUNNY AND TRANQUIL CONDITIONS. MAX TEMPS MID TO UPR 20S DUE TO LITTLE MIXING AND FRESH SNOW. HIGH PRESSURE THEN SETTLES OVER THE SOUTHEASTERN STATES FRIDAY NIGHT THROUGH SUNDAY. COLD AGAIN SATURDAY MORNING WITH MINIMA AROUND 10F FOR MANY INTERIOR LOCATIONS...TEENS MORE LIKELY WHERE MIXING PERSISTS. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... BROAD TROUGH CROSSES THE UPR MIDWEST TO THE NRN MID-ATLANTIC MONDAY...THOUGH IT APPEARS CLOUD COVER WOULD BE THE ONLY SENSIBLE WEATHER. OTHERWISE...A WELCOME CALM WEATHER PATTERN WITH A WARMING TREND. A FEW DEGREES WARMER ON MAX TEMPS EACH DAY IN SWLY FLOW...LOW 40S FOR SATURDAY...MID 40S N...MID 50S S MONDAY. 60S POSSIBLE SOUTH OF DC TUESDAY THROUGH THURSDAY. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... IFR CONDITIONS OR LOWER HAS COMMENCED AT ALL TERMINALS DUE TO A BAND OF HEAVY SNOW. SN WILL LIGHTEN DURING THE AFTERNOON...WITH CONDITIONS IMPROVING DURING THE EVENING. VFR IS EXPECTED LATER OVERNIGHT. WINDS GENERALLY N OR NW...SOME GUSTS UP TO 20 KT POSSIBLE TODAY. HIGH PRESSURE BUILDS OVERHEAD FRIDAY WITH VFR/TRANQUIL CONDS. COLD AGAIN FRIDAY NIGHT WITH MIN TEMPS IN THE TEENS TO 10F. SWLY FLOW AND MORE HIGH PRESSURE SATURDAY THROUGH THE FIRST HALF OF NEXT WEEK. && .MARINE... SCA CONDITIONS EXPECTED TO DEVELOP TODAY AND PERSIST THROUGH TONIGHT FOR ALL WATERS WITH N/NW WINDS GUSTING 20 TO 25 KT AS COLDER AIR MOVES IN. RAIN WILL CHANGE TO SLEET AND SNOW FROM MID MORNING THROUGH MIDDAY. PRECIP ENDS THIS EVENING BUT WINDS WILL CONTINUE TO GUST TO SCA LEVELS THURSDAY MORNING...WHEN HIGH PRESSURE WILL THEN TAKE CONTROL. SCA CONTINUES FOR SRN MD WATERS FRIDAY MORNING FOR NLY CHANNELING. HIGH PRESSURE BUILDS OVERHEAD FRIDAY AFTERNOON...THEN SETTLES OVER THE SERN STATES THROUGH THE WEEKEND WITH LIGHT SWLY FLOW EXPECTED. && .HYDROLOGY... RAIN AND ICE-INDUCED STREAM RISES HAVE OCCURRED ACROSS MUCH OF THE HYDROLOGIC SERVICE AREA. GUNPOWDER FALLS AT GLENCOE ROSE ABOVE FLOOD STAGE OVERNIGHT DUE TO ICE EFFECTS AND REMAINS ABOVE FLOOD AT THIS TIME. IT ALSO APPEARS EXTREMELY LIKELY THAT THERE IS AN ICE JAM ON THE LOST/CACAPON RIVER IN EASTERN WEST VIRGINIA SINCE THE GAUGE AT GREAT CACAPON HAS MOVED VERY LITTLE DESPITE THE RAIN. WITH THE RAIN NOW CHANGING TO SNOW...THESE ARE THE TWO MOST LIKELY AREAS FOR MINOR FLOODING TODAY...WITH THE THREAT RAPIDLY DECREASING ELSEWHERE. SINCE THERE ARE NO ADDITIONAL PRECIPITATION EVENTS AFTER TODAY FOR AT LEAST A WEEK...THE MELT OF THE CURRENTLY-FALLING SNOW SHOULD BE GRADUAL AND IS UNLIKELY TO POSE A FLOOD THREAT IN THE COMING DAYS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...WINTER STORM WARNING UNTIL 9 PM EST THIS EVENING FOR DCZ001. MD...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MDZ003>006-011-501>508. WINTER STORM WARNING UNTIL 9 PM EST THIS EVENING FOR MDZ013- 014-016-018. WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR MDZ017. VA...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR VAZ025>031-040-501-503>508. WINTER STORM WARNING UNTIL 9 PM EST THIS EVENING FOR VAZ038- 039-050>055-502. WINTER STORM WARNING UNTIL 10 PM EST THIS EVENING FOR VAZ036- 037-056-057. WV...WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR WVZ050>053-055-501>506. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ530>532-535- 536-538>542. SMALL CRAFT ADVISORY UNTIL NOON EST FRIDAY FOR ANZ533-534-537- 543. && $$ SYNOPSIS...BAJ/ADS NEAR TERM...HTS/ADS SHORT TERM...BAJ LONG TERM...BAJ AVIATION...HTS/BAJ/ADS MARINE...ADS/BAJ HYDROLOGY...JE

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