Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 240855 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 355 AM EST MON NOV 24 2014 .SYNOPSIS...
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LOW PRESSURE INTENSIFYING OVER THE GREAT LAKES WILL BRING AN ASSOCIATED COLD FRONT THROUGH THE MID-ATLANTIC LATE THIS AFTERNOON AND EARLY THIS EVENING. LOW PRESSURE IS EXPECTED TO TRACK NORTH ALONG THE COAST WEDNESDAY. HIGH PRESSURE WILL RETURN FOR THURSDAY AND FRIDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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SFC WMFNT HAS JUMPED N OF CWFA. LTST TEMPS E OF THE BLURDG ARND 60F AT 08Z. I-81 CRRDR AND FOOTHILLS LAGGING A BIT BHD...BUT A GUSTY SLY FLOW RESIDES AREAWIDE...SO THE WARM PUSH SHUD ENCOMPASS THE ENTIRE AREA BY DAYBREAK. THE FNT WAS THE MAIN FOCUS FOR PCPN. THUS...THE LGT-MDT STRATIFORM RA ALREADY ACRS THE DELMARVA AND POINTS N OF THERE. HV LGT RESIDUAL SHRA...SPCLY BTWN I-95 AND THE BLURDG DUE TO A SLGT UPSLP COMPONENT. HWVR...THE FORCING FOR THAT WL WANE BY SUNRISE AS WELL. THE CWFA WL BE W/IN STRONG SLY FLOW TDA. THE CDFNT WL DROP INTO AREA AFTR 18Z...BUT IT REMAINS MOISTURE STARVED W/ DYNAMIC FORCING ACRS OF W OF THE OHVLY. THUS...BELIEVE IT WL COME THRU DRY...AND HV PULLED POPS FOR THE REST OF THE DAY. RH PROFILES DO INDICATE HIGH ENUF VALUES IN THE LLVLS FOR CONTD CLDCVR TIL MIDDAY. HWVR...MEAN LYR RH THINS OUT DURING THE AFTN...AND XPCT INCRSG SUNSHN. CONSIDERING THE WARM START AND H8 TEMPS RISING TO 12-14C...HV RAISED MAXT SVRL DEGF. WL HV HIGHS AOA 70F AREAWIDE...AND A CRRDR IN THE MID 70S BALT-DC-EZF.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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RDGG WL BLD ACRS THE CWFA FM THE W TNGT-TUE...FOR A PD OF DRY WX. HWVR...UPR LVL CLDS WL BE INCRSG ONCE AGN TUE AFTN IN ADVC OF AN IMPULSE OVER THE SERN CONUS. ALTHO H8 TEMPS WL BE DROPPING...THE CORE OF THE COOLER AIR WL HANG BACK W OF THE MTNS...ALONG W/ THE CENTER OF THE RDG. THEREFORE...ITS NOT GOING TO GET ALL THAT COLD... JUST COOLER THAN TDA. MIN-T FCST STILL A LTL ABV CLIMO...AND MAXT TUE RIGHT AT CLIMO.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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ACCUMULATING SNOW EXPECTED FOR PARTS OF THE MID-ATLANTIC WEDNESDAY. A 500 MB UPPER LEVEL TROUGH WILL BE ACROSS MOST OF THE CONUS WITH THE AXIS ACROSS THE MID-WEST TUESDAY NIGHT. SFC HIGH PRESSURE WILL MOVE INTO THE REGION AND NRLY WINDS WILL USHER IN COOLER AIR OVERNIGHT. THE COLD FRONT THAT WENT THROUGH THE EASTERN SEABOARD MONDAY NIGHT WILL INTERACT WITH THE WARM WATERS OF THE GULF STREAM TUESDAY NIGHT. A 170+KT JET WILL BE LOCATED ACROSS THE APPALACHIAN REGION WITH THE RIGHT ENTRANCE REGION OF THE JET ACROSS THE SE STATES. THE COLD AIR AND WARM WATER INTERACTION AND UPPER LEVEL DIVERGENCE WILL CAUSE CYCLOGENESIS. THE 500 MB TROUGH WILL TREK EASTWARD INTO WEDNESDAY MORNING AND LOW PRESSURE WILL MOVE UP THE EAST COAST. GUIDANCE IS IN AGREEMENT THAT LOW PRESSURE WILL RAPIDLY DEEPEN OFF THE EAST COAST AS IT MOVES N-NE PARELLEL TO THE EAST COAST. THE EXACT TRACK OF THE LOW MOVES IS STILL UNCERTAIN. THE ECMWF IS CLOSER THAN THE GFS/NAM. TEMPERATURES TUESDAY NIGHT ARE EXPECTED TO REACH THE LOW 30S ACROSS THE HIGHLANDS AND HIGHER ELEVATIONS TO THE MID TO UPPER 30S ACROSS THE I-95 CORRIDOR AND NEAR 40 NEAR THE WATERS. USED SREF TEMPS AS IT HAS BEEN DOING WELL WITH TEMPS FOR THE MID-ATLANTIC. MOISTURE WILL FEED INTO THE LOW WEDNESDAY AND PRECIPITATION WILL OCCUR WEDNESDAY. THE PRECIP SHIELD WILL MOVE INTO THE REGION FROM THE SOUTH LATE TUESDAY NIGHT/WED MORNING. MAX TEMPS FOR THE DAY WILL LIKELY BE REACHED WED MORNING AS PRECIP MOVES QUICKLY INTO THE REGION. DYNAMICAL COOLING WILL ALLOW TEMPS TO DROP FURTHER INTO THE MID 30S...A CRITICAL ZONE. SNOW SHOWERS ARE EXPECTED TO BEGIN IN THE HIGHER ELEVATIONS SUCH AS THE BLUE RIDGE...VA HIGHLANDS AND THE WESTERN SLOPES AS THEY WILL BE NEAR FREEZING IF NOT BELOW. RAIN AND SNOW ARE EXPECTED FURTHER EAST AND IN LOWER LYING AREAS. ALL RAIN IS EXPECTED ACROSS THE NRN PIEDMONT INTO THE DC METRO AND SOUTHERN MARYLAND WED MORNING AS TEMPS WILL BE NEAR 40. WEAK HIGH PRESSURE WILL BE LOCATED NORTH OF THE MID-ATLANTIC WEDNESDAY. TEMPS AROUND FREEZING WILL BE FURTHER NORTH WHILE DEWPTS WILL BE AROUND FREEZING. NRLY WINDS WILL BE ADVECTING IN THESE TEMPS INTO THE MID-ATLANTIC THROUGHOUT THE DAY. NOT TOO EXCITED THAT SNOWFALL ACCUMULATIONS WILL LIKELY BE FROM DYNAMICAL COOLING AND NOT A BELOW FREEZING AIRMASS. WITH THAT BEING SAID WENT WITH THE LOWER SIDE OF GUIDANCE FOR SNOWFALL ACCUMULATION...RAIN AND SNOW SHOWERS ARE EXPECTED TO CHANGE TO SNOW SHOWERS WEDNESDAY AFTERNOON ACROSS THE NORTHWEST SUBURBS OF BALTIMORE AND WASHINGTON DC. THIS WILL LEAD TO ACCUMULATION ACROSS THIS AREA. TAKING THICKNESSES INTO ACCOUNT FROM SREF MEAN...3-5 INCHES OF SNOW IS EXPECTED ACROSS THE N-W SUBURBS OF BALTIMORE AND WASHINGTON DC THROUGH WEDNESDAY. HIGHER AMTS ARE EXPECTED ALONG THE BLUE RIDGE AND PORTIONS OF THE SHENANDOAH VALLEY. TEMPS ALONG I-95 AND FURTHER EAST WILL BE WARMER AND THE RAIN/SNOW LINE WILL LIKELY SETUP ACROSS THE BALTIMORE/WASHINGTON METRO AREA RESULTING IN A SHARP GRADIENT OF SNOWFALL ACCUMULATION. LESS THAN AN INCH IS EXPECTED FOR BALTIMORE/DC AT THIS TIME. THIS COASTAL STORM WILL MOVE OUT QUICK AND SNOW SHOWERS WILL WRAP UP WEDNESDAY EVENING ACROSS THE REGION. ADDITIONAL ACCUMULATION IS EXPECTED. TEMPS WILL DROP INTO THE 20S WEDNESDAY NIGHT/THURSDAY MORNING.
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&& .AVIATION /09Z MONDAY THROUGH FRIDAY/...
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MVFR-IFR FLGT CONDS ATTM...DUE MAINLY TO CIGS. AM XPCTG A SLGT IMPRVMNT THRU DAYBREAK...AND THEN CIGS WL BE LIFTING TO VFR BY NOON. VFR SHUD PREVAIL FOR THE REMAINDER OF THE TAF PD. WNDS WL BE THE OTHER ISSUE. SLY WINDS 15-25 KT ATTM AT THE SFC. LWX VWP INDICATES 40 KT AT 2K FT. HV LLWS GROUP CONTG...ALTHO THE JET AXIS SHUD BE PASSING NE OF TERMINALS SHORTLY /BTWN 09-10Z/. WINDS WL STILL BE STRONG THRUT THE DAY...W/ MEAN LYR MIXING SUGGESTING A FEW GUSTS SHUD REACH AOA 30KT ELY TAFTN. WNDS WL BECOME WLY TNGT..AND DIMINISH TO ARND 10-15 KT. VFR TUE. WLY WINDS CONTG 10-15 KT.
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&& .MARINE...
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SCA ACRS ALL WATERS ATTM...W/ STRONG SCA UP THE BAY. RECENTLY SAW A 33KT GUST AT NAK...WHICH IS ALSO REFLECTED AT TPLM2. WL MONITOR THAT CLOSELY. IF ITS A TREND AND NOT AN OUTLIER...WL EITHER NEED TO RAISE GLW OR ADD A MWS. SUSPECT THE LATTER WL BE THE COURSE OF ACTION. THERE WL BE ANOTHER PEAK IN THE MIXED PROFILE ELY TAFTN WHERE WNDS MAY REACH 30-35 KT. HV CAPPED WNDS AT 30 KT ATTM DUE TO WATER TEMPS IN THE 40S. IF WE NEED TO CHANGE COURSE OF ACTION THIS MRNG...WL NEED TO ADJUST REST OF DAY AS WELL. WNDS WL VEER WLY TNGT AS CDFNT CROSSES WATERS. FNT WL BE LOSING SUPPORT...AND THUS WONT BE XTNDG ONTO CURRENT SCA...WHICH ENDS 01Z MID-UPR PTMC AND 06Z ELSW. A LIGHTER WLY FLOW WL CONT INTO TUE...10-15 KT.
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&& .TIDES/COASTAL FLOODING...
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IN SPITE OF A STRONG SLY FLOW...WATER LVLS HAVE REMAINED NEAR OR BLO ASTRO NORMS. THEREFORE...NO ISSUES EXPECTED TODAY OR TOMORROW.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 AM EST TUESDAY FOR ANZ530>534- 537>543. SMALL CRAFT ADVISORY UNTIL 8 PM EST THIS EVENING FOR ANZ535- 536.
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&& $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...HTS/HAS MARINE...HTS/HAS TIDES/COASTAL FLOODING...HTS

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