Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 221146 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 646 AM EST THU JAN 22 2015 .SYNOPSIS... LOW PRESSURE IS MOVING EAST ACROSS PENNSYLVANIA. HIGH PRESSURE THEN BUILDS INTO THE AREA TONIGHT. A LOW PRESSURE SYSTEM IS EXPECTED TO DEVELOP ALONG THE CAROLINA COAST FRIDAY NIGHT AND TRACK OFF THE DELMARVA SATURDAY. ANOTHER LOW IS EXPECTED TO CROSS THE AREA SUNDAY NIGHT INTO MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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UPDATE... WINTER WEATHER ADVISORY HAS BEEN CANCELLED ACROSS ALL OF THE FORECAST AREA EXCEPT FOR PORTIONS OF THE WASHINGTON DC METRO AND ANNE ARUNDEL COUNTY. LIGHT PRECIPITATION IS MOVING THROUGH THE DISTRICT AND PORTIONS OF FAIRFAX AND AREA INDEPENDENT CITIES. THIS PRECIP CAME THROUGH IAD WITH A TEMP OF 32 DEGREES AND A RAIN/SNOW MIX. WILL LEAVE THE ADVISORY UP AS RAIN MAY FREEZE IN ANY AREAS THAT ARE AT OR BELOW FREEZING. WINTER WX ADVISORY HAS ALSO BEEN CANCELLED OVER THE POTOMAC HIGHLANDS. ANY ADDITIONAL SNOW TODAY SHOULD BE LESS THAN AN INCH. DENSE FOG ADVISORY REMAINS IN EFFECT FOR PORTIONS OF THE SHENANDOAH VALLEY...JEFFERSON COUNTY WV AND WASHINGTON COUNTY MD...WHERE SOME OBS OF 1/4SM PERSISTED AT 11Z. PREVIOUS DISCUSSION... 08Z MSAS ANALYSIS INDICATES BROAD LOW PRESSURE OVER PA...ALONG WITH AN UPPER TROUGH OVER PA AND UPSTATE NY. THIS SYSTEM WILL CONTINUE TO PUSH ACROSS THE MID- ATLANTIC THIS MORNING BEFORE BEING ABSORBED INTO A STRONGER OFFSHORE LOW BY THIS AFTERNOON. BROAD AREA OF LIGHT PRECIPITATION...WITH A FEW POCKETS OF MODERATE PRECIP...HAVE BEEN MOVING ACROSS THE NORTHERN HALF OF THE CWA. MOST OBSERVED PRECIP IS SNOW...WITH SOME OBSERVATIONS REPORTING UNKNOWN PRECIP. MD TRAFFIC CAMS HAVE CONFIRMED AT LEAST A COATING OF SNOW. ALTHOUGH MOST OF PRECIP IS MOVING ACROSS NRN MD...SOME SCATTERED AREAS HAVE CONTINUED TO DEVELOP OVER THE SHENANDOAH VALLEY AND ERN WV. FOR THIS REASON...HAVE NOT REMOVED ANY COUNTIES FROM THE WINTER WX ADVISORY YET. IN ADDITION...LOW LEVEL MOISTURE HAS PERSISTED WITH WIDESPREAD FOG. VSBYS IN MANY AREAS LESS THAN A MILE. A DENSE FOG ADVISORY REMAINS IN EFFECT WEST OF THE BLUE RIDGE AND AN SPS FOR PATCHY DENSE FOG IS IN EFFECT FOR SEVERAL COUNTIES IN THE VA PIEDMONT. WILL CONTINUE TO MONITOR THE NEXT FEW HOURS AND MAKE HEADLINE ADJUSTMENTS IF WARRENTED. DURING THE DAY...THE AREA WILL COME UNDER THE INFLUENCE OF EXPANSIVE HIGH PRESSURE ANCHORED OVER THE MIDWEST. DRIER AIR WILL FILTER IN ALLOWING FOG TO DISSIPATE BY LATE MORNING. ANY MORNING PRECIP WILL ALSO COME TO AN END...EXCEPT POTENTIAL UPSLOPE SNOW OVER THE POTOMAC HIGHLANDS. WINDS MAY ALSO GUST UP TO 15-20 MPH THIS AFTERNOON. HIGH TEMPS TODAY MAINLY IN THE 40S.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... HIGH PRESSURE BUILDS IN TONIGHT...WITH THE RIDGE AXIS OVER THE MID-ATLANTIC BY MORNING. GOOD RADIATIONAL COOLING CONDITIONS WILL RESULT IN LOWS IN THE 20S ACROSS THE AREA...WITH SOME TEENS IN THE HIGHLANDS AND LOW 30S OVER DOWNTOWN WASHINGTON DC AND BALTIMORE. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... FAST FLOW RMNS THE TERM BEST DESCRIBING THE WX PATTERN AS WE MOVE INTO THE LATTER PART OF JAN. HIGH PRES OVR THE RGN ERLY FRI WL BE MOVG OFF THE CST...AND XPCT TO SEE HIGH CLDS ON THE INCRS FRI AFTN AHD OF LOW PRES DVLPG IN THE NRN GULFMEX. HIGHS FRI IN THE U30S/L40S. FRI NGT/SAT MID ALTC WL BE UNDER THE INFLUENCE OF THE LOW AS IT TRANSFERS ENERGY FM THE GULF STATES TO NEAR ORF SAT MRNG. TEMPS FRI NGT XPCTD TO BE A FEW DEGS BLO FRZG. THE 850-1000 TCKNS ARE RIGHT ARND 1300 DM. ONE THING THAT LEADS ME TO THINK P-TYPE LEANS TOWARDS SN IS THAT THE PCPN WL BEGIN OVRNGT. IT IS PSBL THAT THIS WL CHG TO RA ALONG THE WRN SHORE OF THE BAY. THERE MAY ALSO BE A DEGREE OF ELEVATION DEPENDENCY TO THIS EVENT. DURG DAY SAT THE LOW IS XPCTD TRACK E OF THE DELMARVA. HIGHEST POPS WL BE IN THE ERN PART OF THE FCST AREA - ALONG THE BAY PCPN SHOULD CHG TO RA...W OF I-95 A RASN MIX...CHANGING TO ALL SNOW FURTHER W...ALTHO W OF THE BLU RDG POPS WL BE LOWER. PCPN SHOULD BE COMING TO AN END FM SW TO NE DURG THE AFTN. HIGHS GNRLY 35-40. HIGH PRES BRIEFLY RETURNS SAT NGT/SUN...THEN THE NEXT SYSTEM TRACKS RAPIDLY INTO THE MID ATLC COURTESY OF A 140 KT JET AND THE WRN RDG/ERN TROF UPR LVL PATN. ATTM THIS LOW LOOKS TO BE MORE OF A CLIPPER TYPE SYSTM - IT WL NOT BE DIVING INTO THE GULF LK THE SAT STORM. FOR NOW WL KEEP THE CHC OF SN ACROSS THE AREA. IT`S TOO ERLY TO TRY TO GET INTO SPECIFICS. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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IFR/LIFR CONDITIONS OVER THE TERMINALS THIS MORNING WITH LOW CIGS AND FOG. BY LATE MORNING CONDITIONS IMPROVE TO VFR AND REMAIN SO THROUGH THURSDAY NIGHT. THERE MAY BE A FEW HRS OF GUSTY WINDS THIS AFTN. VFR CONDITIONS FRI...W/ INCRSG CLDS FRI NGT EVENTUALLY BCMG SUB- VFR. INCREASING CHC OF IFR OR LOWER LATE FRI NGT/SAT WITH PCPN. CONDS IMPRVG LATE SAT AFTN. NEXT SYSTEM LOOKS TO ARRIVE SUN NGT/MON MRNG. MIDDLE OF NEXT WK - CHILLY TEMPS AS COLD HIGH PRES MOVES OVR THE RGN.
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&& .MARINE... LIGHT WINDS THIS MORNING. NW FLOW WILL DEVELOP BY AFTERNOON. SOME GUSTS INTO THE TEENS LIKELY. WE MAY SEE SCA-LEVEL GUSTS FOR A BRIEF PERIOD...MORE LIKELY LATE IN THE AFTERNOON. CONFIDENCE NOT HIGH ENOUGH YET TO RAISE A SCA...AND IT MAY BE APPROPRIATELY HANDLED WITH A MWS. WILL LET DAY SHIFT MONITOR. SUB-SCA CONDITIONS FRIDAY. SCA LVL WINDS LOOK LKLY SAT AFTN/EVE. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER WEATHER ADVISORY UNTIL 8 AM EST THIS MORNING FOR DCZ001. MD...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR MDZ003. WINTER WEATHER ADVISORY UNTIL 8 AM EST THIS MORNING FOR MDZ013- 014. VA...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR VAZ029>031. WINTER WEATHER ADVISORY UNTIL 8 AM EST THIS MORNING FOR VAZ053- 054. WV...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR WVZ053. MARINE...NONE.
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&& $$ NEAR TERM AND AVIATION UPDATE...KCS

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