Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 181449 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 949 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/...
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SFC HIGH PRESSURE CENTERED NEAR LAKE SUPERIOR WILL EXTEND SE TOWARD THE AREA TODAY...WHILE STILL UNDER THE INFLUENCE WITH THE PRESSURE GRADIENT TO LOW PRESSURE OVER THE CANADIAN MARITIMES. STRATOCUMULUS EXTENDS ACROSS THE NORTHERN THIRD OF THE CWA AND HAS ACTUALLY ADVANCE A BIT BACK TO THE SE OVER THE PAST FEW HOURS. STILL THINK THIS LAYER CAN AT LEAST BECOME MORE SCATTERED WITH DIURNAL MIXING...BUT MAY BE A SLOW PROCESS. ANOTHER SHORTWAVE TROUGH IS QUICKLY APPROACHING FROM THE LOWER OHIO VALLEY. HI RES MODELS CONTINUE TO SHOW PRECIP FIZZLING AS IT ENCOUNTERS DRIER AIR MASS/HIGH PRESSURE...AND THE LAST COUPLE HOURS OF RADAR DATA SUPPORT THE HYPOTHESIS. THERE IS A BETTER LATCHING ONTO THE NORTHERN AREA SURVIVING ACROSS OHIO...SO WILL MONITOR RADAR TRENDS AS TO WHETHER POPS MAY NEEDED TO BE ADDED LATE AFTERNOON/EVENING IN THE NORTHERN MOUNTAINS. OTHERWISE JUST AN INCREASE IN MID LEVEL CLOUDS EXPECTED. EXPECT THE SPORADIC WIND GUSTS TO BECOME MORE COMMON TOWARD MIDDAY AS THE 20-25 KT SEEN ON THE 12Z KIAD SOUNDING ARE ABLE TO MIX DOWN. SOUNDING ALSO SUPPORTS GOING HIGH TEMPERATURES COMBINED WITH A BIT OF DOWNSLOPING...SO NO ADJUSTMENTS THERE. 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.
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&& .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 /15Z THURSDAY THROUGH MONDAY/...
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VFR CONDITIONS TODAY WITH BKN CIGS AT TIMES 040-050 (EXCEPT CHO) AND WIND GUSTS TO 20KT POSSIBLE. CIGS WILL SCATTER OUT BY THIS AFTERNOON. THE GUSTY NW WINDS WILL BECOME MORE CONSISTENT THROUGH THIS AFTERNOON...THEN DIMINISH BY EVENING. 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 SIGNIFICANT WEATHER EXPECTED SATURDAY AND SUNDAY.
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&& .MARINE...
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SCA CALIBER GUSTS WILL CONTINUE THROUGH THE AFTERNOON. MORNING ANALYSIS SUGGESTS NW GUSTS 20-25 KT WITH MIXING. THESE WINDS WILL DIMINISH THROUGH THE AFTERNOON...NO CHANGES TO THE SCA DROPPING OFF AT 19Z FOR THE UPPER POTOMAC AND 00Z ELSEWHERE. 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.
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&& .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...ADS/HTS SHORT TERM...HTS LONG TERM...HAS AVIATION...ADS/HAS/HTS MARINE...ADS/HAS/HTS

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