Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 051950
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
250 PM EST THU MAR 5 2015

.SYNOPSIS...
LOW PRESSURE WILL CONTINUE TO PUSH WELL SOUTH AND EAST OF THE
AREA LATE THIS AFTERNOON. HIGH PRESSURE WILL BUILD OVERHEAD
TONIGHT THROUGH FRIDAY BEFORE DRIFTING TO THE SOUTH THIS WEEKEND
INTO EARLY NEXT WEEK.
&&

.NEAR TERM /THROUGH TONIGHT/...
AS PRVSLY PROGGED...BAND OF HVY SNW HAS DROPPED ACRS CENTRL VA
AND SRN MD. THIS IS THE AREA WHERE MID-LVL FGEN FORCING RESIDES.
WHEN THE FORCING AND LIFT COMBINED OVER CENTRAL MD/ERN WVA/NRN VA
SNOWFALL RATES OF 1-2 INCHES/HR WERE OBSRVD. BASED ON OBS SINCE
18Z...BELIEVE THE SAME OCCURRING OVER CENTRL VA ATTM. THAT WL
QUICKLY MAKE UP FOR THE LACK OF SNOW DURING THE MRNG. MINOR
ADJUSTMENTS MADE TO SNOW TTL MAP. END RESULT A WIDESPREAD 4-8
INCHES...W/ A CPL BANDS UP TO 10 INCHES PSBL.

ACCUMULATING SNOW WILL WIND DOWN DURING THE MID-LATE AFTERNOON
HOURS AS CNVGNC SLIDES SE OF THE AREA. HWVR...RRQ OF UPR JET WL
ARRIVE AS MID- LVL FORCING DEPARTS. THAT SUGGESTS THAT FLURRIES
MAY LINGER INTO THE EVNG. STILL HV ACCUM SNOW /FRACTION OF AN
INCH/ INTO ELY EVNG ACRS SRN MD. NO ADDTL SNOWFALL XPCTD ELSW.

MEAN LYR RH DROPS RAPIDLY OVNGT...WHICH SHUD ALLOW CLDS TO SCATTER
OUT. MEANWHILE THE DRY ARCTIC AMS WL CONT TO STREAM IN. KEPT A
MIN-T FCST THAT FOCUSED ON A MOS MEAN...LWRG BY A DEGF OR TWO FOR
THE FRESH SNOW AND CLRG SKIES. WHILE WINDS SHUD DIMINISH OVNGT...
DONT BELIEVE THEY WL OUTRIGHT DCPL. THAT COMBO PLACES OUTLYING
AREA OF CWFA...FM DC/BALT NWRN BURBS TO BLURDG WWD...AT THE
THRESHOLD FOR WIND CHILL ADVY. OPTED IN TO ALERT SNOW STORM
RECOVERY EFFORTS.
&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
HIPRES BLDS INTO CWFA FRIDAY. NRN STREAM S/WV ENERGY WL OVERRIDE
RDG...WHICH WL ERASE THE SUNNY START TO THE DAY. XPCT MOCLDY TO
PREVAIL DURING THE AFTN-EVE HRS.

THE THERMAL TROF WL BE CROSSING THE AREA DURING THE DAY. AS A
RESULT...FRI WL BE A COOLER DAY W/ MAXT IN THE MID-UPR 20S AND
MIN-T 10-15F.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
AS WAS THE CASE YESTERDAY...NOT MUCH HAS CHANGED FROM PREVIOUS
FORECASTS FOR THE EXTENDED PERIOD. WHILE SOME WARMING BEGINS
SATURDAY...SNOW COVER WILL LIKELY TEMPER THIS TREND INITIALLY. HIGHS
SATURDAY WILL REMAIN BELOW NORMAL...WITH HIGHS IN THE 40S NORTH AND
50S SOUTH.

LIGHT LOW-LEVEL WESTERLY FLOW DEVELOPS OVERNIGHT SATURDAY AND
CONTINUES THROUGH THE DAY SUNDAY. RAISED MAX TEMPS A FEW DEGREES
ABOVE GUIDANCE TO ACCOUNT FOR SOME DOWNSLOPE WARMING. OVERNIGHT LOWS
SUNDAY WILL FINALLY BE ABOVE FREEZING...EXCEPT IN HIGHER ELEVATIONS
WHERE UPPER 20S WILL BE MORE COMMON. EXPECT THIS TREND TO CONTINUE
WITH NIGHTTIME LOWS REMAINING AOA FREEZING THROUGH THE EXTENDED.
DAYTIME HIGHS WILL ALSO RETURN TO NEAR NORMAL. KEPT TUESDAY A LITTLE
COOLER THAN THE REST OF THE WEEK DUE TO POTENTIAL CLOUD COVER FROM
APPROACHING SYSTEM. STILL UNCLEAR IF THIS SYSTEM WILL AFFECT OUR
AREA OR SKIRT TO OUR SOUTH...FOR NOW LEFT SCHC POPS IN OUR FAR
SOUTHERN ZONES TO ACCOUNT FOR THIS.
&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
SNOW WILL GRADUALLY SLIDE SOUTH AND EAST LATE THIS AFTERNOON ACROSS
THE TERMINALS. IFR CIGS/VSBYS ARE EXPECTED IN SNOWFALL THROUGH LATE
THIS AFTERNOON. CONDITIONS WILL QUICKLY IMPROVE THIS EVENING AS HIGH
PRESSURE BUILDS TOWARD THE TERMINALS. NORTH-NORTHWEST WINDS AROUND 5
TO 10 KNOTS ARE EXPECTED. THE NORTH-NORTHWEST FLOW WILL CONTINUE
THROUGH FRIDAY WITH VFR CONDITIONS.

EXPECT VFR CONDITIONS THROUGH THE WEEKEND.
&&

.MARINE...
SCA CONDITIONS HV YET TO REALLY DVLP TDA...ASIDE FM AN OCNL GUST.
STILL BELIEVE POTL EXISTS AS COLDER AIR MOVES IN AND PCPN MOVES
OUT. IN FACT...THE LACK OF PCPN MAY FACILITATE FULL MIXING. HV SCA
CONDS FOR ALL WATERS TNGT...AND ADJUSTED CONTINUATION INTO FRI
MRNG FOR THE BAY.

WINDS WILL BE LIGHT OVER THE WEEKEND...SO NOT EXPECTING
ANY MARINE CONCERNS THROUGH THIS PERIOD.
&&

.HYDROLOGY...
RAIN AND ICE-INDUCED STREAM RISES HAVE OCCURRED ACROSS MUCH OF THE
HYDROLOGIC SERVICE AREA. MANY OF THE STREAMS HAVE NOW CRESTED AND
ARE FALLING. IT IS VERY LIKELY THAT THERE IS AN ICE JAM ON THE
LOST/CACAPON RIVER IN EASTERN WEST VIRGINIA ABOVE GREAT CACAPON THAT
HAS NOT YET BROKEN...BUT WITH COLD AIR NOW BACK IN PLACE...IT MAY
NOT UNTIL TEMPERATURES WARM AGAIN...KEEPING RISES GRADUAL FOR NOW.

ALSO APPEARS THERE MAY BE SOME SORT OF ICE EFFECT ON GOOSE CREEK
BETWEEN EVERGREEN MILLS AND LANSDOWNE. THE CURRENT STAGE/FLOW AT THE
EVERGREEN MILLS GAUGE IS HIGHER THAN WOULD BE EXPECTED BASED ON
UPSTREAM SITES...AND STILL RISING. STILL A FEW FEET BELOW FLOOD
STAGE AT THIS TIME.

SINCE THERE ARE NO ADDITIONAL PRECIPITATION EVENTS AFTER TODAY FOR
AT LEAST A WEEK...THE MELT OF THE NEWLY-FALLEN SNOW SHOULD BE
GRADUAL. SO THE FLOOD THREAT FROM THAT SHOULD BE MINIMAL BUT WILL BE
MONITORED NEXT WEEK.

&&

.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.
     WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST FRIDAY
     FOR MDZ003>006-501>507.
     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.
     WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST FRIDAY
     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.
     WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 10 AM EST FRIDAY
     FOR WVZ050>053-055-501>506.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST FRIDAY FOR ANZ532>534-537-
     540-541-543.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST FRIDAY FOR ANZ530-531-535-
     536-538-539-542.

&&

$$
SYNOPSIS...BJL/HTS
NEAR TERM...HTS
SHORT TERM...HTS
LONG TERM...MSE
AVIATION...BJL/MSE
MARINE...HTS/MSE
HYDROLOGY...JE



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