Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 040051
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
751 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/...

MUCH OF THE AREA CURRENTLY IN THE WINT WX ADVSRY...NRN 1/2 OF
CWA...IS PCPN FREE. IN DC/S OF PTMC TEMPS ARE SLTLY ABV FRZG W/
SRLY WINDS. WE MAY DROP SOME THE ADVSRY WHICH IS IN EFFECT UNTIL
10 PM ERLY.

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.

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.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
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
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 /01Z 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 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.

&&

.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...
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.
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 FROM 1 AM TO 7 AM EST THURSDAY FOR
     ANZ530>543.

&&

$$
UPDATE...WOODY!
PRVS...KRW/HTS/MSE


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