Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 082008 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 308 PM EST MON FEB 8 2016 .SYNOPSIS...
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A LOW PRESSURE SYSTEM OVER THE GREAT LAKES WILL REFORM NEAR THE MID-ATLANTIC COAST TONIGHT AND MOVE AWAY THROUGH TUESDAY NIGHT. HIGH PRESSURE WILL REMAIN POSITIONED WEST OF THE AREA FOR THE MIDDLE AND LATTER PARTS OF THE WEEK.
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&& .NEAR TERM /THROUGH TUESDAY/...
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COMPLEX WINTER WX SCENARIO WILL BE UNFOLDING ACROSS THE REGION OVER THE NEXT 24 HOURS. DEEP UPPER TROUGH OVER THE GREAT LAKES AND OHIO VALLEY WILL BE EXPANDING TOWARD THE EAST COAST. SFC LOW PRESSURE OVER THE GREAT LAKES WILL EVENTUALLY TRANSFER ENERGY TO A COASTAL LOW LATER TONIGHT. AN INVERTED TROUGH WILL EXTEND BACK FROM THE LOW INTO THE MID-ATLANTIC STATES. A WINTER STORM WARNING IS IN EFFECT FOR NORTH CENTRAL MD...WITH WINTER WX ADVISORIES FOR THE REMAINDER OF THE NORTHERN CWA AND WESTERN MOUNTAINS. THE FIRST WAVE OF PRECIP IS PUSHING INTO THE MOUNTAINS. HOWEVER IT IS SHOWING A WEAKENING TREND AND WILL BE ENTERING A FAIRLY DRY AIRMASS. THEREFORE IT MAY TAKE A WHILE FOR ANYTHING APPRECIABLE TO MAKE IT TO THE GROUND UNTIL AT LEAST THIS EVENING IN MANY AREAS. PRECIP THROUGH THE FIRST HALF OF THE NIGHT IS EXPECTED TO BE LIGHT AND SOMEWHAT INCONSISTENT. INITIALLY PRECIP WILL FALL AS RAIN IN MANY LOCATIONS...WITH A GRADUAL CHANGEOVER TO A MIX AND THEN EVENTUALLY SNOW. THERMAL PROFILES SE OF US-29 WILL REMAIN MARGINAL FOR THE LONGEST PERIOD. LOW TEMPS WILL BARELY TOUGH FREEZING IN THESE AREAS. MODERATE SNOW WILL EVENTUALLY DEVELOP OVER NORTHERN MD IN RESPONSE TO THE INVERTED TROUGH...AND THIS IS WHERE THE HIGHEST TOTALS ARE EXPECTED. DRIER AIR IS STILL EXPECTED TO WORK INTO SOUTHERN PARTS OF THE CWA ON TUESDAY...WHILE THE INVERTED TROUGH AND MOST PERSISTENT SNOWS WILL STAY ACROSS NORTHERN MD. THERE MAY STILL BE SOME BREAKS AT TIMES...WHICH WILL HELP WITH COMPACTION/SETTLING AND MELTING AS HIGH TEMPS WILL RISE NEAR OR ABOVE FREEZING. SO OVERALL THIS WILL BE A PROLONGED EVENT OF LIGHT TO MODERATE SNOW...POSSIBLY MIXING WITH RAIN AT TIMES SOUTH AND EAST OF DC. MORE THAN 6 INCHES IS EXPECTED NORTH OF BALTIMORE...WITH A SHARP CUTOFF ACROSS THE DC METRO AREA. NAM/GFS INDICATING A SECONDARY BAND OF PRECIP SOUTH OF DC FOR TUESDAY AFTERNOON...BUT THIS HAS ONLY BEEN INCORPORATED IN A BLENDED SENSE FOR NOW. IN TERMS OF UNCERTAINTY...THERE ARE STILL A WIDE RANGE OF QPF TOTALS AND PLACEMENTS...EXPECTED WITH A STORM SYSTEM THAT WILL HAVE MESOSCALE FEATURES. SFC TEMPS WILL ALSO BE MARGINAL IN MANY AREAS (PLENTY COLD ALOFT)...WHICH COULD AFFECT TOTALS. FOR NOW HEADLINES ARE FOCUSED ON AREAS OF HIGHER CONFIDENCE...WITH FURTHER CHANGES POSSIBLE.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
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SNOW WILL GRADUALLY PULL AWAY TO THE NE TUESDAY NIGHT...BUT THE UPPER LEVEL TROUGH WILL MAKE THE DRYING PROCESS SLOW. A PROLONGED PERIOD OF UPSLOPE SNOW IS EXPECTED...WITH TOTALS OF 5-10 INCHES POSSIBLE...ALTHOUGH THE ACCUMULATIONS WILL BE SPREAD OUT AND HAVE THUS ONLY ISSUED AN ADVISORY AT THIS TIME. WHILE THERE WILL NOT BE A DEFINED VORT MAX ROTATING THROUGH ON WEDNESDAY AND WEDNESDAY NIGHT...THE UPPER TROUGH AND STEEP LAPSE RATES IN THE DGZ SUGGEST SNOW SHOWERS OR FLURRIES WILL BE POSSIBLE ACROSS MUCH OF THE AREA. IF MORE PRONOUNCED FORCING BECOMES EVIDENT...POPS MAY BE ABLE TO BE ADJUSTED UPWARD. WITH CONTINUED CAA...EXPECT HIGHS IN THE 20S AND 30S WITH LOWS IN THE TEENS AND 20S. WIND CHILLS COULD DROP BELOW ZERO IN THE POTOMAC HIGHLANDS BY WEDNESDAY NIGHT AND WILL CONTINUE TO MENTION THIS IN THE HWO.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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UPPER LEVEL TROUGH AXIS WILL REMAIN OVER/NEAR OUR REGION THROUGH THE WEEKEND... WITH CAA KEEPING THE TEMPS WELL BELOW NORMAL DURING THIS PERIOD. UPSLOPE SNOW SHOWERS PSBL BEFORE THIS TROUGH MOVES AWAY ON SUN... AND SOME SHOWERS COULD MAKE IT EAST OF THE BLUE RIDGE. SFC HIGH PRESS BUILDS IN ON SUN WITH DRIER CONDITIONS... BEFORE A COLD FRONT/UPPER SHORTWAVE APPROACHES ON MON BRINGING ADDITIONAL PRECIP TO OUR CWA. HIGH TEMPS THU AND FRI WILL BE IN THE 20S AND 30S... THEN IN THE 20S FOR SAT AND SUN... INCREASING TO THE 20S AND 30S ON MON. LOW TEMPS WILL BE IN THE SINGLE DIGITS TO THE TEENS THROUGH THIS PERIOD... WITH SAT NIGHT BEING THE COLDEST NIGHT WITH TEMPS IN THE SINGLE DIGITS... AND BELOW ZERO FOR UPPER ELEVATIONS. WIND CHILLS COULD BE A CONCERN DUE TO GUSTY WINDS... MAINLY ON THU AND SAT.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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LOWERING CIGS INTO THIS EVENING...EVENTUALLY REACHING IFR LATER TONIGHT. PRECIP WILL INITIALLY BE LIGHT...BUT COULD INCREASE IN INTENSITY FROM LATE EVENING THROUGH THE REST OF THE NIGHT FOR THE NORTHERN TERMINALS. CHANGEOVER TO SNOW MAY BE RATHER QUICK WITH THE EXCEPTION OF DCA...WHICH MAY BE THE LATTER HALF OF THE NIGHT...AND MAY NOT COMPLETELY CHANGE OVER DEPENDING ON INTENSITY. KEPT A PROLONGED PERIOD OF IFR THROUGH TUESDAY...WITH DETAILS EVENTUALLY TO BE IRONED OUT WITH A MARGINAL RAIN/SNOW EVENT OF VARYING INTENSITY. WINDS SHOULD GENERALLY BE LESS THAN 10 KT THROUGH THE TAF PERIOD. CONDITIONS SHOULD GRADUALLY IMPROVE TUESDAY NIGHT. A SNOW SHOWER WILL REMAIN POSSIBLE THROUGH WED/WED NIGHT. MAINLY VFR CONDITIONS EXPECTED OVER THE TERMINALS DURING THIS PERIOD. SOME SNOW SHOWERS PSBL. GUSTY WINDS EXPECTED ON THU.
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&& .MARINE...
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LOW PRESSURE WILL BE DEVELOPING NEAR THE COAST TONIGHT AND PULLING AWAY TUESDAY. SOME INDICATION THIS EVENING AS EASTERLY FLOW DEVELOPS THERE COULD BE A BRIEF PERIOD OF SCA CONDITIONS...BUT CONFIDENCE IN THAT IS NOT HIGH AT THIS TIME. WINDS WILL BECOME NW OR W BY TUESDAY NIGHT...AND SCA CONDITIONS WILL LIKELY DEVELOP DURING THIS TIME. THE STRONG FLOW WILL CONTINUE THROUGH WED AND WED NIGHT. SCA CONDITIONS PSBL THU DUE TO GUSTY WINDS... THEN BECOMING SUB- SCA ON FRI AS WINDS DECREASE. SOME SNOW SHOWERS PSBL.
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&& .TIDES/COASTAL FLOODING...
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WATER LEVELS ARE INCREASING AS A SE FLOW HAS DEVELOPED. THE EVENING HIGH TIDE WILL HAVE TO BE MONITORED DEPENDING ON HOW QUICKLY THE WATER LEVELS RISE. THE FOLLOWING CYCLE MAY HAVE A BETTER CHANCE AT EXCEEDING MINOR THRESHOLDS AT SENSITIVE SITES. WINDS INCREASE OUT OF THE W AND NW LATER TUESDAY...WHICH SHOULD ALLOW THE WATER LEVELS TO DECREASE...WITH A BETTER CHANCE OF BLOWOUT TIDES LATER WEDNESDAY/THURSDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO MIDNIGHT EST TUESDAY NIGHT FOR DCZ001. MD...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO MIDNIGHT EST TUESDAY NIGHT FOR MDZ013-504. WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR MDZ003-502. WINTER STORM WARNING FROM 10 PM THIS EVENING TO 6 AM EST WEDNESDAY FOR MDZ004>006-011-014-503-505>508. WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR MDZ501. VA...WINTER WEATHER ADVISORY FROM 10 PM THIS EVENING TO MIDNIGHT EST TUESDAY NIGHT FOR VAZ052>054-501-505-506. WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR VAZ027-028-030-031-504. WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR VAZ503. WV...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR WVZ050>053-055-502-504-506. WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR WVZ501- 503-505. MARINE...NONE.
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&& $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...IMR AVIATION...ADS/IMR MARINE...IMR TIDES/COASTAL FLOODING...ADS

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