Area Forecast Discussion
Issued by NWS Sterling, VA

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605
FXUS61 KLWX 082008
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
308 PM EST MON FEB 8 2016

.SYNOPSIS...
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.

&&

.NEAR TERM /THROUGH TUESDAY/...
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.

&&

.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 /20Z MONDAY THROUGH SATURDAY/...
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.

&&

.MARINE...
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.

&&

.TIDES/COASTAL FLOODING...
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.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
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.

&&

$$
SYNOPSIS...ADS
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...IMR
AVIATION...ADS/IMR
MARINE...IMR
TIDES/COASTAL FLOODING...ADS



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