Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 032324 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 624 PM EST TUE MAR 3 2015 .SYNOPSIS... A WARM FRONT WILL LIFT THROUGH THE AREA TONIGHT. A COLD FRONT WILL MOVE INTO THE REGION WEDNESDAY FOLLOWED BY HIGH PRESSURE FOR THURSDAY LASTING INTO THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/...
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AT 6 PM RCVD REPORT OF 1/16 INCH OF FZRA IN WRN ALLEGANY CO SO ADDED THEM TO THE ADVSRY. FIRST BATCH OF FREEZING RAIN MIXED WITH A LITTLE SLEET WILL PUSH OUT OF THE BALTIMORE METRO AREA AND BE REPLACED WITH INTERMITTENT FREEZING DRIZZLE/LIGHT FREEZING RAIN THIS EVENING. WARMER AIR HAS BEEN SLOW TO PUSH NORTH AS WE HAVE SEEN MUCH OF THIS WINTER. THE VAST MAJORITY OF THE WARMING HAS OCCURRED OVER WESTERN AND SOUTHERN PORTIONS OF THE FORECAST AREA BUT COLD WEDGE HAS REMAINED IN PLACE FURTHER NORTH. AREAS TO THE NORTH AND WEST OF BALTIMORE...ESPECIALLY NEAR THE MASON DIXON LINE WILL SEE THE GREATEST IMPACT FROM ICING WHICH COULD SEE UPWARDS OF 0.10-0.15 INCHES OF ICE. THERE IS STILL HIGH CONFIDENCE THAT WARM ADVECTION WILL WIN OUT AND TEMPERATURES WILL GRADUALLY RISE ABOVE FREEZING LATER TONIGHT IN ALL AREAS. AFTER MIDNIGHT...EXPECT LIGHT RAIN...SOME FOG AND MILDER TEMPERATURES. A COMPLEX FRONTAL SYSTEM WILL BEGIN TO IMPACT THE MIDDLE ATLANTIC REGION ON WEDNESDAY. AHEAD OF THE FRONT...MILDER AIR WILL PUSH NORTH INTO THE FORECAST AREA...THOUGH NOT TO THE EXTENT THAT PREVIOUS GUIDANCE SUGGESTED. MUCH OF THE AREA WILL BE SHROUDED IN CLOUD COVER AND PERIODS OF LIGHT RAIN. TEMPERATURES WILL LIKELY TOP OUT IN THE 40S IN MOST LOCATIONS WITH PERHAPS THE LOWER TO MIDDLE 50S CENTRAL VA TO SOUTHERN MD. KEPT POPS CATEGORICAL ALL DAY WEDNESDAY. PRECIPITATION SHOULD REMAIN AS LIQUID IN ALL AREAS THROUGH 00Z THURSDAY.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... GDNC CONTS TO PAINT AN ANOMOLOUS PICTURE...DRAINING COLD AIR SOUTH WED NGT IN WAKE OF CDFNT. WHILE THERES NOT A STRONG LOW OR PVA... THERES PLENTY OF FORCING AVBL THX TO STRONG BAROCLINIC ZONE AND RRQ OF UPR JETMAX. A STREAM OF AMPLE MSTR WL BE OVERRUNNING THE COLD AIR...SOURCED FROM THE WRN GLFMEX AND PACIFIC. THEREFORE...IT SEEMS WELL WITHIN REASON TO HAVE QPF CONTG WHILE TEMPS DROP BELOW FREEZING. THAT SUPPORTS A SCENARIO WHERE RAIN WILL CHG TO SNOW. THERE ARE STILL TIMING QUESTIONS AS WELL AS WHETHER THE ENTIRE COLUMN WILL COOL IN UNISON. IF NOT...THEN PTYPE MAY BE MORE PL AND LESS SNOW. THAT IS MORE OF A CONCERN ACROSS CENTRAL VA AND SRN MD. IN ADDITION...THERE IS STILL A RANGE OF SOLUTIONS WRT HOW MUCH QPF WL FALL AS SOMETHING FROZEN. SOLUTIONS SEEM TO BE COMING IN COOLER AND WETTER. GIVEN THE RANGE OF POSSIBILITIES...DO NOT WISH TO UNDERSTIMATE POTENTIAL. FCST ACCUMS HV BEEN RAISED A BIT ACRS THE NORTH...WHERE STDY SNOW SEEMS APPARENT. DID NOT DO LIKEWISE ACRS THE S DUE TO THE PL POTENTIAL. REGARDLESS...AT THE 50 PCT CONFIDENCE LVL...SEE ENUF EVIDENCE TO RAISE A WATCH FOR THE ENTIRE AREA. PCPN WL CONT INTO THU AFTN. COLD AIR CONTS TO STREAM SWD THU NGT AFTR PCPN ENDS. STUCK CLOSE TO A PRVS FCST/MOS CONSENSUS FOR MIN-T THU NGT. HV PLENTY OF LOWS IN THE SINGLE DIGITS. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AFTER A VERY COLD START FRIDAY MORNING...TEMPERATURES WILL STRUGGLE TO RISE DURING THE DAY IN THE CONTINUED WEAK CAA...WITH HIGHS REMAINING BELOW FREEZING OVER MUCH OF THE AREA. DESPITE THE RETURN OF SOUTHERLY WINDS OVERNIGHT FRIDAY...TEMPERATURES WILL STILL BE VERY COLD. WENT A LITTLE WARMER THAN GUIDANCE FOR FRIDAY NIGHT AND SATURDAY DUE TO THE INCREASED WEAK WAA. WEAK COLD FRONT ASSOCIATED WITH LOW PRESSURE WELL TO OUR NORTH SLIDES THROUGH THE AREA SATURDAY AFTERNOON/EVENING WITH LITTLE EFFECT ON SENSIBLE WEATHER...EXCEPT FOR A WIND SHIFT. THERE IS A CHANCE OF SOME UPSLOPE SNOW SHOWERS IN THE FAR WEST...BUT LEFT POPS OUT OF FORECAST UNTIL A CLEARER SIGNAL APPEARS. BEYOND SATURDAY MODEL GUIDANCE BECOMES NOISIER WITH VARYING MODEL SOLUTIONS...SO WENT WITH A BLEND OF HPC AND MODEL GUIDANCE. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... SUB VFR CONDITIONS EXPECTED AT ALL TERMINAL SITES THROUGH WEDNESDAY. LIGHT WINTRY PRECIPITATION WILL REMAIN POSSIBLE MAINLY FROM KIAD NORTH TO KMRB...KBWI AND KMTN. FRZRA OR FZDZ WILL BE MOST COMMON WITH THE MAJORITY OF ICING ISSUES AT KBWI AND KMTN. ALL PRECIPITATION WILL TRANSITION TO PLAIN RAIN LATER THIS EVENING EXCEPT LATER TONIGHT NEAR THE MASON DIXON LINE. PATCHY FOG...MVFR TO IFR CIGS AND VSBYS EXPECTED INTO WEDNESDAY WITH PERIODS OF LIGHT RAIN EXPECTED. AOB IFR WL CONT WED NGT-THU DUE TO MAINLY SNOW. IMPRVG CONDS THU NGT. DO NOT ANTICIPATE ANY AVIATION CONCERNS THIS WEEKEND. && .MARINE...
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SCA WINDS NOT CURENTLY BEING XPRNCD ON THE WATERS. THIS WL BE ALLOWED TO END AT 7 PM. SCA CONDITIONS MAY BE POSSIBLE OVER A PORTION OF THE WATERS ON WEDNESDAY. VISIBILITIES WILL BE REDUCED DUE TO SOME FROZEN PRECIPITATION THIS EVENING THEN RAIN TONIGHT AND WEDNESDAY. RAIN AT THE BGNG OF WED EVNG WL TRANSITION TO SNW AND PSBLY SOME PL. AS COLD AIR DRAINS SWD...MIXING WL IMPRV. HV RAISED A SCA WED NGT TO ACCT FOR THAT...WHICH LKLY WL NEED TO CONT INTO AT LEAST THU. WITH LIGHT AND VARIABLE WINDS THROUGH MUCH OF THE PERIOD... DO NOT ANTICIPATE ANY MARINE CONCERNS FRIDAY THROUGH SUNDAY.
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&& .HYDROLOGY... THROUGH WEDNESDAY AFTERNOON...AROUND A HALF TO THREE QUARTERS OF AN INCH OF RAIN IS EXPECTED...EXCEPT FOR HEAVIER AMOUNTS THAT COULD APPROACH 1.0 - 1.5 INCHES ALONG THE ALLEGHENY FRONT. TEMPERATURES WILL RISE WELL INTO THE 40S EVERYWHERE /AND 50S IN THE RAPPAHANNOCK AND JAMES RIVER BASINS/...PROMOTING SNOWMELT. THE SNOWPACK IS CURRENTLY ESTIMATED TO BE HOLDING ANYWHERE FROM A HALF INCH OF WATER IN THE CACAPON/LOST RIVER BASIN TO AROUND AN INCH AND A HALF IN THE SOUTH BRANCH POTOMAC BASIN. MODELING INDICATES NOT ALL OF THIS SNOW WATER WILL BE RELEASED...ESPECIALLY GIVEN A TOTAL LACK OF SUNSHINE. GIVEN THIS...THE COMBINATION OF SNOWMELT AND RAIN WILL PROMOTE RISES ON AREA RIVERS...BUT AT THIS TIME STREAMS ARE LIKELY TO REMAIN WITHIN-BANK. SOME COMPLICATING FACTORS TO KEEP IN MIND...IF THE CHANGEOVER FROM RAIN TO WINTRY PRECIP ON WEDNESDAY EVENING OCCURS LATER THAN EXPECTED...CONCERNS MAY BECOME HEIGHTENED. ALSO MANY OF OUR AREA STREAMS ARE COVERED WITH ICE OR EVEN PARTIALLY FROZEN. THESE EFFECTS WILL HAVE TO BE MONITORED FOR A POTENTIAL ROLE IN AFFECTING RUNOFF. LASTLY...AS WE SAW WITH THE RECENT RAIN/ICE/MINOR SNOWMELT...ANY AMOUNT OF LIQUID PRECIPITATION STANDS A GOOD CHANCE OF CAUSING MINOR POOR DRAINAGE FLOODING...AS NORMAL DRAINAGE PATTERNS MAY BE BLOCKED BY PLOWED SNOW. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR DCZ001. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR DCZ001. MD...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR MDZ003>006-011-013-014-501>508. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR MDZ016>018. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR MDZ003>006-011-013-014-501>508. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MDZ016>018. VA...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR VAZ026>031-040-052>054-501-503>507. WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING FOR VAZ025-036>039-050-051-055>057-502-508. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR VAZ053-054-505-506. WV...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY EVENING FOR WVZ050>053-055-501>506. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR WVZ051>053. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ530>543. SMALL CRAFT ADVISORY FROM 1 AM TO 7 AM EST THURSDAY FOR ANZ530>543.
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&& $$ UPDATE...WOODY! PRVS...KRW/HTS/MSE

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