Area Forecast Discussion
Issued by NWS Sterling, VA

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000 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/...
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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.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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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.
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&& .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/...
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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.
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&& .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...
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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.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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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.
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&& $$ UPDATE...WOODY!/JCE PRVS...APS/HTS/CAS

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