Area Forecast Discussion
Issued by NWS Sterling, VA

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273
FXUS61 KLWX 091446
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
946 AM EST TUE FEB 9 2016

.SYNOPSIS...
MULTIPLE LOW PRESSURES IMPACT THE REGION THROUGH WEDNESDAY BEFORE
PUSHING OFF TO THE NORTHEAST. HIGH PRESSURE BUILDS IN THE WAKE
THROUGH FRIDAY. A QUICK MOVING COLD FRONT SWINGS THROUGH FRIDAY
NIGHT WITH CANADIAN HIGH PRESSURE BUILDING IN FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...

WE HV BEEN WATCHING RDRS/TRAFFIC CAMS/SPOTTER REPS/AIRPORT OBS TO
GET A BETTER HANDLE ON WHAT CHGS NEED TO BE MADE TO THE FCST. WE
HV RCVD SOME REPS OF 3-4 INCHES IN NRN MONT UP TO THE PA BRDR. BUT
WE HV 4-5 INCHES IN THE TOTAL SNOW ACCUM GRIDS...AND GIVEN THE
RLTV SPOTTINESS OF THE HVIER SN ON RDR WE FEEL THAT IT WOULD ONLY
BE AN ISOLD SPOT THAT RCVD ANYTHING HIGHER THAN 5 INCHES...SO WE
WL LV THE FCSTD TOTALS AS IS...AND KEEP CENTRAL MD IN AN ADVSRY.

WE HV ALSO RCVD A COUPLE REPS OF 1-3 INCHES IN ROCKINGHAM CO.
TRAFFIC CAMS SHOWING SNOW ON GRASS ALONG I-81 OF VARYING SMALL
AMTS. RDR NOT SHOWING ANY ECHO THERE...SO AM NOT GOING TO ISSUE AN
ADVSRY THERE BECAUSE PCPN IS ENDING.

COASTAL FLOOD ADVSRY HAS BEEN UPDATED TO WRNG FOR A PORTION OF THE
BAY. PLS REFER TO THE COASTAL FLOOD SXN BLO FOR MORE DETAILS.

LOW PRES ORGANIZING OFF SRN DELMARVA. AS THIS DEEPENS...PUSHING
OFF TO THE NE...EXPECT AN INVERTED TROUGH EXTENDING BACK ACROSS
MD INTO PA TO ACT AS TRIGGER FOR PCPN DEVELOPMENT OVER THE
EASTERN HALF OF THE CWA INTO THIS AFTN.

WITH THE UPPER LVL TROUGH IN PLACE...A POTENT SHORTWAVE MOVES
INTO WESTERN VA...WHICH WILL ACT AS THE TRIGGER FOR SNOW SHOWERS
FOR THE WESTERN HALF OF THE CWA. AS IT MOVES OVER DELMARVA THIS
EVENING...THE PCPN AREA WILL TRANSITION...LEADING TO DRYING OVER
CENTRAL VA.

&&

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

HIGHER CONFIDENCE IN THE MIDWEEK FORECAST AS THE FOCUS TURNS FROM
PCPN THREAT AND MORE INTO THE MUCH COLDER TEMPS. WITH THE
DEPARTING LOW...EXPECTING NW FLOW TO PERSIST THRU THIS
TIME...KEEPING UPSLOPE SNOW SHOWERS IN THE FORECAST THRU THURSDAY.
THE WINTER WX ADVISORY FOR THE ALLEGHENY FRONT IS IN EFFECT THRU
THURS WITH BETWEEN 6 AND 10 INCHES PSBL FROM NOW TILL THEN.
OUTSIDE OF THE UPSLOPE SNOW...AS THE UPPER LVL TROUGH PIVOTS
EAST...ENOUGH ENERGY ALOFT COULD TRIGGER AN ISO SNOW SHOWER ALONG
THE MASON-DIXON...THOUGH WITH THE MUCH DRIER AIRMASS IN PLACE...IT
WILL BE DIFFICULT AND IT MAY END UP BEING MORE JUST FLURRIES.

FOR THE TEMPS...WED WILL BE SLIGHTLY COOLER THAN TODAY...WITH THE
FIRST SURGE OF CAA COMING IN DURING THE DAY...DROPPING LOWS WED
NIGHT INTO THE SINGLE DIGITS AND TEENS. WIND CHILL ADVISORIES MAY BE
NEEDED FOR THE ALLEGHENY FRONT WITH WIND CHILLS DROPPING TO BELOW
-10 DEGREES. THE THREAT WILL BE PSBL AGAIN THURS NIGHT.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...

ARCTIC AIR WILL BE REINFORCED FRI-SAT BY ANOTHER DISTURBANCE WITHIN
H5 TROF. GDNC SUGGESTING THAT THE LEADING EDGE WL TRACK NORTH OF THE
AREA FRI...ALLOWING SHSN TO BE CAUGHT IN THE MTNS...FOLLOWED BY A
GREATER PUSH LATE FRI NGT/ELY SAT MRNG. NW WINDS AND SGFNT CAA WL
FOLLOW THAT. LTST GDNC SUGGESTING THAT MAXT SAT WL BE IN THE TEENS
PTMC HIGHLANDS/20S ELSW. WIND CHILLS WILL BE A CONCERN THEN...AND WL
ONLY BE AMPLIFIED SAT NGT AS TEMPS FALL INTO THE SINGLE DIGITS--EVEN
IN THE CITIES OF DC/BALT. SUBZERO TEMPS FCST IN THE MTNS. WL HV A
GRADUAL MODERATING TRENDS BY THE START OF THE NEW WEEK...PERHAPS
WITH ANOTHER ROUND OF POTL PCPN.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...

IFR/MVFR CIGS CURRENTLY BEING OBSERVED ACROSS THE TAF SITES WITH
LIGHT RAIN IMPACTING ALL BUT KCHO. CIGS/VIS WILL IMPROVE TO MVFR
THIS AFTN WITH THIS TRANSITION. SNOW AMTS WILL BE LESS THAN ONE
INCH KCHO/KDCA...1-3 KIAD/KBWI...AND 2-4 KMRB/KMTN.

THE PCPN WILL TAPER OFF COMPLETELY BY TONIGHT WITH VFR CONDITIONS
THEN EXPECTED TONIGHT THRU THURSDAY. WINDS DURING THE TAF PERIOD
WILL BE NE LESS THAN 10 KTS...BCMG NW AND INCRSG THIS AFTN...WITH
GUSTS PSBL TONIGHT. GUSTY NW WINDS WILL CONTINUE WED-THURS.

VFR MOST LKLY FRI-SAT. WINDS SAT CUD GUST NW 20-25 KT.

&&

.MARINE...

SUB-SCA CONDITIONS ON ALL WATERS THROUGH TODAY. INCRSG NW
WINDS TONIGHT WILL PRODUCE OCNL SCA GUSTS ON THE CHESAPEAKE
BAY...BCMG MORE PERSISTENT AND WIDESPREAD THURSDAY AND THURSDAY
NIGHT.

WINDS FRIDAY WL BE ON THE LGT SIDE...AS WE/LL BE IN A WK HIPRES RDG
AHD OF ANOTHER TROF AXIS. THAT AXIS/REINFORCING FNT WL CROSS WATERS
BEFORE SAT AM. SCA CONDS XPCTD DURING THE DAY...AND MOST LKLY
LINGERING THRU THE NGT.

&&

.TIDES/COASTAL FLOODING...

ELEVATED TIDAL LEVELS CONTINUE...WITH TIDAL ANOMALIES STILL SITTING
AT 2.5 FEET ABOVE NORMAL. DO NOT EXPECT THESE ANOMALIES TO DROP
UNTIL WINDS SHIFT LATER TODAY. AS A RESULT...HAVE REVISED OUR TOTAL
WATER LEVEL FORECASTS UPWARD FOR THE UPCOMING TIDE CYCLE. ST GEORGES
ISLAND IS NOW EXPECTED TO REACH MODERATE FLOOD AGAIN THIS AFTERNOON
AND A WARNING HAS BEEN ISSUED FOR ST MARYS COUNTY. ANNAPOLIS WILL BE
REALLY CLOSE AND IT WILL DEPEND ON IF AND WHEN WINDS PICK UP OUT OF
THE WEST. IN FACT...IF WE DO NOT LOSE SOME OF THIS ANOMALY /WHICH
HAS NOT YET BEGUN TO OCCUR/...GIVEN THAT THE NEXT HIGH TIDE IS
ASTRONOMICALLY HIGHER...THE TOTAL WATER LEVEL COULD EQUAL OR PERHAPS
EVEN EXCEED THIS MORNING. AM RIGHT ON THE FENCE OF ISSUING COASTAL
FLOOD WARNINGS FOR BALTIMORE/ANNE ARUNDEL/CALVERT...THIS WILL HAVE
TO BE CLOSELY MONITORED TODAY.

DC WATER LEVELS ARE EQUALLY ELEVATED...AND IF A BLOWOUT DOES START
TO OCCUR...THEY WOULD BE FIRST. HOWEVER...ONLY A 1.2 FOOT ANOMALY IS
NEEDED TO REACH MINOR FLOOD WITH THE NEXT HIGH TIDE. CURRENT
ADVISORY FOR DC METRO HAS BEEN EXTENDED TO NOON. CONFIDENCE IS TOO
LOW TO EXTEND FURTHER YET BUT A REISSUANCE IS POSSIBLE LATER TODAY
DEPENDING ON THE ANOMALY TREND.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL NOON EST TODAY FOR DCZ001.
MD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR
     MDZ003>006-011-013-014-502>508.
     COASTAL FLOOD ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ011-
     014-016-018-508.
     WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR MDZ501.
     COASTAL FLOOD WARNING UNTIL 5 PM EST THIS AFTERNOON FOR MDZ017.
     COASTAL FLOOD ADVISORY FROM 5 PM THIS AFTERNOON TO 5 AM EST
     WEDNESDAY FOR MDZ017.
VA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR VAZ027-
     028-030-031-501-504>507.
     WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR VAZ503.
     COASTAL FLOOD ADVISORY UNTIL NOON EST TODAY FOR VAZ054.
WV...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR
     WVZ050>053-055-502-504-506.
     WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR WVZ501-
     503-505.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM WEDNESDAY TO 6 AM EST THURSDAY
     FOR ANZ531-532-539-540.
     SMALL CRAFT ADVISORY FROM 1 AM TO 6 AM EST THURSDAY FOR ANZ535-
     536.
     SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EST
     THURSDAY FOR ANZ533-534-537-541-543.
     SMALL CRAFT ADVISORY FROM 9 AM WEDNESDAY TO 6 AM EST THURSDAY
     FOR ANZ530-538-542.

&&

$$
UPDATE...WOODY!/JCE
PRVS...APS/HTS/CAS



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