Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 090233 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 933 PM EST MON FEB 8 2016 .SYNOPSIS...
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A LOW PRESSURE SYSTEM OVER THE GREAT LAKES WILL EXPAND EAST TO THE MID-ATLANTIC COAST TONIGHT AS THE SYSTEM DRIFTS EAST 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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AS OF 9PM...1001MB SFC LOW ON N SIDE OF LAKE ERIE WITH A TROUGH EXTENDING DOWN TO N-CNTRL NC. UPR LOW CENTER IS OVER NRN IN PER WATER VAPOR IMAGERY. MEANWHILE...DEVELOPED LOW IS SE OF NOVA SCOTIA. 1033MB SFC HIGH IS OVER LABRADOR. SECONDARY SFC LOW WILL DEVELOP OFF SFC TROUGH OVER SERN VA OVERNIGHT...THEN DEVELOP FURTHER EAST OFF THE DELMARVA TUESDAY MORNING AS THE TROUGH PIVOTS OVER THE AREA. RAIN WITH SNOW ABOVE ABOUT 700 FT HAS SPREAD EAST AHEAD OF THIS SFC TROUGH. TEMPERATURES HAVE BEEN SLOW TO DECREASE ACROSS THE AREA...BUT WILL DROP TO THE WET BULB TEMPERATURE/NEAR FREEZING AT LOW ELEVATIONS AS PRECIP PIVOTS EAST. 18Z GFS CONTINUES IDEA OF STRENGTHENING BANDS OF SNOW AS THE SFC LOW DEVELOPS OVERNIGHT THROUGH TUESDAY MORNING. THIS LOW TRACK HAS SHIFTED SOUTH JUST A BIT...SO THE FORECAST WAS UPDATED THIS EVENING WITH MORE SNOW SOUTH OF DC. AS WILL NOTE NEXT...THIS IS LOOKING TO BE A WET SNOW THAT WILL TAKE AWHILE TO STICK TO ROADWAYS. EXPECT NARROW BANDS OF SNOW ON THE ELY FLOW NORTH OF THE SFC LOW WITH A SHARP CUTOFF TO THE SOUTH OF THE LOW LATE TONIGHT THROUGH TUESDAY MORNING. BEST FEATURE OF THIS ACTIVITY IS HIGH LOW LEVEL LAPSE RATES THAT PROMOTES BANDED PRECIP. COMPLICATING THE SITUATION ARE MARGINAL TEMPS ON THE ELY FLOW. NORMALLY HIGH PRESSURE TO THE NORTH PROVIDES DRY AIR AND COLDER CONDITIONS. HOWEVER...SINCE THIS IS SQUEEZED BETWEEN THE GREAT LAKES LOW AND NOVA SCOTIA LOW...THE HIGH IS SHUNTED ALL THE WAY TO LABRADOR. WITH MARGINAL TEMPERATURES...THE SNOW ACCUM WILL BE RATHER ELEVATION DEPENDENT...WITH NOTABLY MORE SNOW MERE HUNDREDS OF FEET HIGHER MSL. LEFT HEADLINES IN PLACE...EXCEPT FOR ADDING THE NRN BLUE RIDGE ZONE FOR 2-4 INCHES. THIS SNOW IS EXPECTED TO BE MORE THAN 12 HRS IN LENGTH...OUR 24 SNOW WARNING CRITERIA IS 7 INCHES ACROSS THE AREA EAST OF THE ALLEGHENY MOUNTAINS. THEREFORE...4-6 INCHES WARRANTS AN ADVISORY OVER 24 HRS...NO WARNING EXPANSION AS OF THIS TIME. TUESDAY AFTERNOON...LOW SHIFTS EAST WITH THE UPR TROUGH AXIS MOVING TO THE ALLEGHENY MOUNTAINS. BANDS OF SNOW ARE EXPECTED TO DEVELOP IN NWLY FLOW IN THE AFTERNOON. LOCATION OF THESE BANDS ARE NOT CERTAIN...BUT 18Z GFS FEATURES TYPICAL NWLY FLOW AREAS ACROSS MD...WITH A SECONDARY BAND OVER N-CNTRL VA TO THE NRN NECK. TEMPERATURES WILL BE MARGINAL FOR THE SRN BAND...BUT THIS MAY BE THE MOST NOTABLE SNOW FOR CULPEPER AND SE. MAX TEMPS HELD BELOW GUIDANCE PER ANTICIPATED CLOUDS/PRECIP.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... 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. && .LONG TERM /THURSDAY THROUGH MONDAY/... 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. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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CIGS CONTINUE TO LOWER THIS EVENING...EVENTUALLY REACHING IFR OVERNIGHT. RAIN WILL BE LIGHT AT FIRST...THEN INTENSIFY 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. SNOW WILL BE IN BANDS...SO IT MAY BE MORE PERIODIC IFR VSBYS IN SNOW. SELY FLOW BECOMES ELY THROUGH TONIGHT BEFORE BECOMING NWLY TUESDAY AFTERNOON...GENERALLY 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. SELY FLOW 10 TO 15 KT BECOMES ELY TONIGHT. 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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TIDAL ANOMALIES HAVE RISEN SHARPLY WITH THE HIGH TIDE THIS EVENING. COASTAL FLOOD ADVISORIES ISSUED FOR ANNE ARUNDEL AND ST MARYS FOR THE MOST SENSITIVE SITES. CURRENT TREND WOULD WARRANT MOST OR ALL OF THE MD WRN SHORE AND EXTENSION FOR DC/ALEXANDRIA. WILL CONTINUE TO MONITOR THROUGH TUESDAY MORNING. WINDS SHIFT TO W/NW TUESDAY AFTERNOON...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 UNTIL MIDNIGHT EST TUESDAY NIGHT FOR DCZ001. COASTAL FLOOD ADVISORY UNTIL 10 PM EST THIS EVENING FOR DCZ001. MD...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR MDZ013-504. WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR MDZ003-502. WINTER STORM WARNING UNTIL 6 AM EST WEDNESDAY FOR MDZ004>006- 011-014-503-505>508. COASTAL FLOOD ADVISORY FROM 3 AM TO 7 AM EST TUESDAY FOR MDZ014. WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR MDZ501. COASTAL FLOOD ADVISORY FROM MIDNIGHT TONIGHT TO 5 AM EST TUESDAY FOR MDZ017. VA...WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR VAZ052>054-501-505-506. WINTER WEATHER ADVISORY UNTIL MIDNIGHT EST TUESDAY NIGHT FOR VAZ027-028-030-031-504-507. WINTER WEATHER ADVISORY UNTIL 6 PM EST WEDNESDAY FOR VAZ503. COASTAL FLOOD ADVISORY UNTIL 10 PM EST THIS EVENING FOR VAZ054. 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...BAJ/ADS NEAR TERM...BAJ SHORT TERM...ADS LONG TERM...IMR AVIATION...BAJ/ADS/IMR MARINE...BAJ/IMR TIDES/COASTAL FLOODING...BAJ

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