Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180840 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 340 AM EST THU DEC 18 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD INTO THE AREA TODAY AND PERSIST THROUGH FRIDAY NIGHT...EXCEPT FOR A WEAK DISTURBANCE THAT WILL CROSS THE AREA TONIGHT. LOW PRESSURE WILL TRACK SOUTH OF THE AREA SATURDAY THROUGH SUNDAY. A SECONDARY LOW IS EXPECTED TO MOVE UP FROM THE SOUTHEAST COAST EARLY NEXT WEEK. A LARGE AREA OF LOW PRESSURE LOOKS TO DEVELOP IN THE OHIO VALLEY DURING THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... SFC HIPRES ACRS THE UPR MIDWEST HAS A RDG AXIS EXTENDING FM IT TWD CWFA. ALSO EVIDENT ON WATER VAPOR/STLT/RADAR COMPOSITE IS A S/WV ENTERING THE LWR OHVLY. FINALLY...THERES A NRN STREAM TROF AXIS... WHICH COVERS THE UPR OHVLY W/ CLDS. THESE HV SPREAD FM THERE ACRS NRN CWFA. NAM DOING BEST AT CAPTURING THE LYR OF RH /THO ITS A LTL TOO LOW IN CLD HGTS/...AND HV USED IT IN POPULATING SKYCVR. THINK WE MAY STILL HV SOME CLDS AT SUNRISE ACRS MD...BUT THEY SHUD MIX OUT SOON THEREAFTER AS UPR SUPPORT DEPARTS. SUBSIDENCE SHUD PREVAIL FOR MUCH OF THE DAYLIGHT HRS. ATM LOOKS WELL MIXED IN THE WAKE OF THE TROF...AND HV NW WNDS UP TO 20 KT. WL BE COOLER THAN YDA...BUT QSTN IS HOW COOL...SPCLY CONSIDERING THERE WL BE COMPRESSIONAL WARMING AND FCST WAS TOO COOL YDA. DID NOT GO QUITE AS LOW AS NAM DUE TO THAT...BUT DID SHADE FCST DOWNWARD. WL HV SOME CLDS FM THE SYSTEM IN THE CENTRL OF THE CONUS ADVCG EWD BY END OF THE PD. WL BE MOCLDY AS A RESULT IN THE EVNG AS WV CROSSES CWFA. NAM SUGGESTING SCHC POPS...MAYBE DUE TO A FLURRY OR TWO. AMS LOOKS TOO DRY FOR THAT. WENT LWR THAN NAM POPS...PRECLUDING A MENTION...BUT POP GRIDS NONZERO. TOOK TEMPS DOWN BY A CPL DEGF IN CAA. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... OVERALL SYNOPTIC PTTN FRI SIMLR TO TDA...MINUS THE S/WVS. HV FEWER CLDS IN THE GRIDS...AND SIMLR TEMPS. AFTR MIDNGT...WL HV MID DECK CLDS FILLING IN FM THE SW...BUT FCST PACE OF STORM SYSTEM HAS SLOWED...WHICH IMPACTS SKYCOVER. NE OF PTMC RIVER SKYCOVER MAY AVG OUT NO WORSE THAN PTCLDY. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE WILL BE CENTERED OVER QUEBEC AND EXTEND DOWN INTO THE MID-ATLANTIC SATURDAY. A SHORTWAVE TROUGH WILL BE APPROACHING THE OHIO VALLEY AND SOUTHERLY FLOW ALOFT WILL CAUSE MOISTURE ADVECTION INTO THE REGION SATURDAY CAUSING CLOUDS TO BUILD IN FROM THE SOUTHWEST. A JET STREAK WILL BE LOCATED ACROSS THE SE STATES WITH MOST OF THE FORCING ACROSS THIS REGION INCLUDING THE CAROLINAS SATURDAY INTO SATURDAY NIGHT. FLOW AT 850 VEERS WESTERLY ACROSS THE MID-ATLANTIC SAT AFTERNOON AND SHUTS OFF MOISTURE ADVECTION FROM THE GULF. THIS WILL RESULT IN LIGHTER PRECIP ACROSS THE REGION. MOST OF THE MOISTURE WILL BE FURTHER SOUTH AND ACROSS THE CAROLINAS. THE 3Z SREF MEAN HAS LINED UP MORE WITH THE DETERMINISTIC RUNS SHOWING MOSTLY DRY CONDITIONS SATURDAY INTO SUNDAY. TEMPS ARE EXPECTED TO CLIMB INTO THE 40S SATURDAY AND ANY PRECIP WILL BE RAIN WITH THE EXCEPTION OF THE HIGHER ELEVATIONS THAT WOULD SEE SNOW. LIGHT PRECIP IS EXPECTED AND THEREFORE LITTLE TO NO ACCUMULATION OF SNOW IN THE MTNS IS EXPECTED AT THIS TIME. THE SHORTWAVE TROUGH WILL MOVE OFF THE EAST COAST BY SUNDAY AND RIDGING WILL ALLOW DRIER AIR TO FILTER IN FROM THE WEST. A BRIEF PERIOD OF CALM WEATHER IS EXPECTED SUNDAY BEFORE THE NEXT SYSTEM BEGINS TO FORM OFF THE SE COAST SUNDAY NIGHT. A TROUGH WILL MOVE INTO THE GULF COAST STATES AND CYCLOGENESIS IS EXPECTED TO TAKE PLACE OFF THE SOUTHEAST COAST MONDAY INTO TUESDAY. TEMPS ARE FORECAST TO BE ABOVE FREEZING WITH THE EXCEPTION OF THE HIGHER ELEVATIONS MONDAY NIGHT. MOSTLY RAIN IS EXPECTED DURING THIS TIME. LOW PRESSURE SHOULD MOVE AWAY FROM THE MID-ATLANTIC TUESDAY. LITTLE RELIEF IS EXPECTED AS THE NEXT STRONG SYSTEM MOVES INTO THE GREAT LAKES REGION MIDWEEK. TIMING IS EVERYTHING AND MOISTURE WITH THIS SYSTEMS SEEMS TO BE PRE-FRONT AND THEREFORE THE MID=ATLANTIC WOULD SEE MOSTLY RAIN. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... VFR FLGT CONDS...W/ BKN CIGS 040-050 AND WINDS OCNLY G20KT. CIGS WL SCATTER OUT ARND DAYBREAK. GUSTY NW WINDS WL BECOME MORE CONSISTENT BY MID MRNG...AND SHUD CONT THRU AT LEAST MID AFTN. WL HV A PD OF MID DECK CLDS THIS EVNG. THINK WNDS WL SUBSIDE AT THE SFC...BUT WL STILL HV 20-25 KT FLOW 1000 FT UP. NOT ENUF TO QUALIFY FOR LLWS. VFR CONTS FRI-FRI NGT. ANTHR PD OF GUSTY NW WINDS MIDDAY UP TO 20 KT. ONCE AGN...MID DECK CLDS WL OVERSPREAD TERMINALS AT NGT. NO FLIGHT RESTRICTIONS ARE EXPECTED SATURDAY AND SUNDAY. && .MARINE... SPORADIC SCA CALIBER WNDS ON THE WATERS ATTM. THESE WL BECOME MORE CONSISTENT AFTR DAYBREAK. MOMENTUM TRANSFER SUGGESTS 20-25 KT BY MIDDAY...AND HAS IT LINGERING A LTL BIT LONGER. HV XTNDD ADVY FOR ALL WATERS BY A CPL HRS...AND THE MAIN CHANNEL/LWR PTMC A BIT LONGER TOO. GDNC SUGGESTING THAT FLOW WL PARTIALLY DCPL TNGT. AM NOT CERTAIN OF THAT...BUT WL CAP WNDS JUST BLO FOR THE NIGHT TIME PD. THE OPPORTUNITY FOR MIXING RENEWS AFTER SUNRISE FRI. HV ISSUED ANTHR SCA FOR MOST OF THE BAY AND LWR PTMC RIVER THRU MID AFTN. A DISTURBANCE WILL MOVE SOUTH OF THE WATERS SATURDAY AND SUNDAY. AN ACTIVE PERIOD IS EXPECTED NEXT WEEK. COASTAL LOW PRESSURE MAY IMPACT THE WATERS MONDAY. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR ANZ530>534-537>543. SMALL CRAFT ADVISORY FROM 7 AM TO 3 PM EST FRIDAY FOR ANZ531>534-537>543. SMALL CRAFT ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR ANZ535- 536. && $$ SYNOPSIS...HTS NEAR TERM...HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...HTS/HAS MARINE...HTS/HAS

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