Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 040715 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 215 AM EST WED MAR 4 2015 .SYNOPSIS... A COLD FRONT WILL MOVE INTO THE REGION WEDNESDAY NIGHT FOLLOWED BY HIGH PRESSURE FOR THURSDAY NIGHT LASTING INTO THE WEEKEND. && .NEAR TERM /THROUGH TODAY/...
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HAD TO ISSUE A SHORT FUSE FREEZING RAIN ADVISORY FOR NORTHERN BALTIMORE AND HARFORD COUNTIES AS LIGHT RAIN IS MOVING THROUGH WITH MULTIPLE MESONETS AT 31-32 DEGREES. TRACE AMOUNTS OF ICE ON COLD SURFACES. PREVIOUS... 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 /TONIGHT THROUGH THURSDAY NIGHT/...
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GDNC CONTS TO PAINT AN ANOMALOUS 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 UNDERESTIMATE 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.
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&& .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 /07Z WEDNESDAY THROUGH SUNDAY/... SUB VFR CONDITIONS EXPECTED AT ALL TERMINAL SITES THROUGH WEDNESDAY. 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... SCA CONDITIONS MAY BE POSSIBLE OVER A PORTION OF THE WATERS ON WEDNESDAY. VISIBILITIES WILL BE REDUCED DUE TO RAIN 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. && .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. && .CLIMATE... AS EVERYONE CAN ATTEST THIS WAS ONE OF THE COLDEST FEBS ON RECORD. W/ THE DC CHERRY BLOSSOM FESTIVAL PLANNED FOR 3/28-4/12 I TOOK A LOOK AT PAST COLD FEBS AND WHEN PEAK BLOOM OCCURRED. GOING BACK TO 1921...IT APPEARS THAT 2015 (AVG TEMP 30.3 AT DCA) HAD THE 4TH COLDEST FEB FOR THE PD. THE FIVE COLDEST....AND THE PEAK BLOSSOM DATES (FM NPS.GOV WEB SITE): YR FEB AVG TEMP MAR AVG TEMP PEAK BLOOM DATE 1934 24.6 41.2 4/15 1979 28.4 51.5 4/2 1936 29.6 50.3 4/7 2015 30.3 ?? ?? 2007 30.9 47.7 4/1 && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR DCZ001. MD...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR MDZ003>006-011-013-014-501>508. WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING FOR MDZ016>018. FREEZING RAIN ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR MDZ006-507-508. VA...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR VAZ026>031-040-052>054-501-503>507. WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING FOR VAZ025-036>039-050-051-055>057-502-508. WV...WINTER STORM WATCH FROM THIS EVENING THROUGH THURSDAY EVENING FOR WVZ050>053-055-501>506. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR ANZ530>543. SMALL CRAFT ADVISORY FROM 1 AM THURSDAY TO 6 AM EST FRIDAY FOR ANZ530>543.
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&& $$ UPDATE...ADS PREVIOUS...WOODY!/KRW/HTS/MSE

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