Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 231232 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
732 AM EST TUE DEC 23 2014

.SYNOPSIS...
WEAK LOW PRESSURE WILL TRACK UP THE MID-ATLANTIC COAST TODAY.
STRONGER LOW PRESSURE WILL PUSH NORTH ALONG THE APPALACHIANS ON
WEDNESDAY...SENDING A COLD FRONT EASTWARD WEDNESDAY NIGHT. BREEZY
CONDITIONS WILL FOLLOW THE FRONT ON THURSDAY...THEN HIGH PRESSURE
WILL BUILD BACK INTO THE REGION TO CLOSE OUT THE WEEK.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
UPDATE...CANCELLED FRED/CAR CO`S FROM FZRA ADZY. TEMPS ACROSS THE
REMAINDER OF THE ADZY HAVEN`T BUDGED AND MAY NEED TO EXTENDED
FURTHER IN TIME BUT WILL MONITOR TRENDS HERE POST-DAWN.

HIGH PRESSURE REMAINED WEDGED THROUGH THE MID-ATLANTIC
OVERNIGHT...WHILE LOW PRESSURE WAS LOCATED ACROSS SOUTHEAST
VIRGINIA.

WEDGE LOOKS LIKE IT WILL HOLD STRONG TODAY/TONIGHT AS LOW PRESSURE
WEAKENS AS IT MOVES NORTHEAST. FOR THE TIME BEING...MUCH OF THE
MEASURABLE PRECIP HAS EXITED THE CWA WITH AREAS OF DRIZZLE LEFT IN
ITS WAKE ESPECIALLY OVER WESTERN/CENTRAL MD AND EASTERN WV. WITH
SOME MESONETS STILL 30-32F...THERE ARE LIKELY POCKETS OF FREEZING
DRIZZLE OCCURRING WHICH IS WHY FREEZING RAIN ADVISORY WAS EXTENDED
TIL 6 AM LATE LAST EVENING.

NEXT BATCH OF MEASURABLE RAIN OVER SOUTHWEST VIRGINIA WILL LIFT
NORTHEAST THROUGH DAYBREAK. CONCERN IS WHETHER TEMPERATURES WILL BE
ABLE TO RISE ANY BEFORE THIS AFFECTS THOSE AREAS THAT ARE NEAR
FREEZING. IF THIS DOESN/T HAPPEN...MAY NEED TO EXTEND THE ADVISORY A
FEW HOURS LONGER AND POSSIBLY EVEN CONSIDER THROWING IN A COUPLE
MORE COUNTIES. WILL CONTINUE TO MONITOR TEMPERATURES CLOSELY.

OTHERWISE...TEMPERATURES SHOULD VERY GRADUALLY RISE TODAY. PREFER
THE LOWER MET GUIDANCE GIVEN THE SYNOPTIC SITUATION. RAIN IN THE
MORNING LIKELY BECOMES MORE OF A DRIZZLE/FOG SET UP THIS
AFTERNOON/EARLY EVENING BEFORE THE NEXT ROUND OF RAIN COURTESY OF
ISENTROPIC LIFT ARRIVES THIS EVENING. BY THEN...TEMPERATURES ACROSS
THE ENTIRE CWA SHOULD BE WARM ENOUGH FOR LIQUID. IN
FACT...TEMPERATURES MAY BE STEADY OR SLOWLY RISE OVERNIGHT.

LOW LEVEL JET STRENGTHENS ON WEDNESDAY...PUSHING A PLUME OF NEAR 1.5
INCH PW/S INTO THE MID-ATLANTIC. PERIODS OF MODERATE RAIN MAY BE
HEAVY AT TIMES. DESPITE DECENT WIND NOT TOO FAR OFF THE
DECK...INSTABILITY IS EXPECTED TO RESIDE SOUTH OF THE CWA AND THUS
SEVERE WX IS NOT EXPECTED.

CONTINUED TO LEAN TOWARD THE LOWER SUITE OF GUIDANCE /MET/ FOR
MAXIMA WEDNESDAY GIVEN THE EROSION OF THE WEDGE AND THEN PERIODS OF
RAIN. THIS BRINGS 50S THROUGH THE CWA...BUT CONFIDENCE IN 60 OR
ABOVE IS LOW.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
DEEPENING SFC LOW /PRESSURES FALLING THROUGH THE 980S MB/ AND
VIGOROUS UPPER LEVEL TROUGH WILL BE LIFTING THROUGH THE GREAT LAKES
THURSDAY NIGHT. THE TRAILING COLD FRONT WILL CROSS THE CWA. USED A
BLEND OF THE 00Z ECMWF AND GFS FOR MOST OF THE WX ELEMENTS AS THEY
MIRROR THE MODEL CONSENSUS. THIS PUSHES THE FRONT OFF THE DELMARVA
BY 12Z. SHOULD SEE A SHARP CUT OFF IN PRECIP BEHIND THE FRONT...BUT
LINGERED SOME POPS IN THE EAST AFTER DAYBREAK IN CASE A SLOWER
SOLUTION TAKES PLACE. MODELS ARE INDICATING A HUNDRED OR TWO J/KG OF
MUCAPE AHEAD OF THE FRONT...ALTHOUGH IT MAY NOT BE DEEP ENOUGH TO
CONSISTENTLY PRODUCE THUNDER. THEREFORE KEPT THE SLIGHT CHANCE OF
THUNDER IN THE EAST WHERE A SLIGHTLY MORE UNSTABLE PROFILE WILL
EXIST. NONETHELESS...PRECIP WILL BE A MORE SHOWERY DURING THIS TIME
FRAME...AND WITH UNSEASONABLY HIGH PWAT VALUES...SOME MODERATE TO
HEAVY ELEMENTS OF RAIN COULD EXIST. FOR AN AREAL AVERAGE THOUGH...IT
APPEARS AMOUNTS WILL BE UNDER A HALF INCH. 40-50 KT WINDS WILL BE
LOCATED A FEW THOUSAND FEET ABOVE MSL...BUT THE TEMP PROFILE WILL
NOT BE SUPPORTIVE OF THESE MIXING DOWN CONSISTENTLY. HOWEVER...WILL
HAVE TO MONITOR THE WIND FORECAST FOR THE PEAKS...AS IT MAY BE CLOSE
TO ADVISORY CRITERIA. EVEN THOUGH TEMPERATURES WILL BE FALLING IN
THE WEST BEHIND THE FRONT...ONLY THE HIGHEST ELEVATIONS HAVE A
CHANCE OF SEEING A CHANGEOVER TO SNOW ONCE THE UPSLOPE ENVIRONMENT
TAKES OVER.

TIGHT PRESSURE GRADIENT WILL BE IN PLACE THURSDAY...SO EXPECT BREEZY
CONDITIONS IN A CAA/DOWNSLOPE ENVIRONMENT. GOOD CONSENSUS ON 20-30
KT GUSTS. SCT/BKN STRATOCU MAY BE MORE PREVALENT IN THE NORTHERN
PART OF THE CWA. THE MOST FAVORABLE TIME FOR UPSLOPE RAIN/SNOW
SHOWERS WILL BE IN THE MORNING...WITH MOISTURE PROFILES THINNING
DURING THE AFTERNOON AS HIGH PRESSURE BUILDS IN FARTHER. WHILE HIGH
TEMPERATURES WILL BE COOLER THAN WEDNESDAY...THEY WILL STILL BE
ABOVE NORMAL. HIGH PRESSURE WILL BE CENTERED OVER THE CAROLINAS BY
LATE THURSDAY NIGHT. WINDS WILL DIMINISH AND LOWS WILL DROP TO
EITHER SIDE OF FREEZING.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
HIGH PRESSURE WILL DRIFT OFF THE MID ATLANTIC COAST FRIDAY AND
SATURDAY. TEMPERATURES WILL BE ABOVE NORMAL. A COLD FRONT WILL
APPROACH FROM THE WEST SATURDAY NIGHT...BUT IT WILL BE MOISTURE
STARVED WITH A THE HIGHEST CHANCE OF LIGHT PRECIP IN THE MOUNTAINS.
MODEL SOLUTIONS THEN DIVERGE WITH HOW TO HANDLE UPPER LEVEL ENERGY
EMERGING FROM THE DESERT SOUTHWEST AND HOW IT INTERACTS WITH THE
FRONT WHICH BECOME MORE PARALLEL TO THE UPPER FLOW. WHILE THE
FORECAST WILL SHOW A HIGHER CHANCE OF PRECIP SUNDAY...THE LATEST 00Z
GUIDANCE SUGGESTS IT MAY BLEED OVER INTO MONDAY. TEMPERATURES WILL
BE COOLER BEHIND THE FRONT AND THUS THERE COULD BE SOME PTYPE
CONCERNS...BUT THERE WILL BE A LACK OF A TRUE ARCTIC AIR SOURCE.

&&

.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
GIVEN THE WEDGE/CAD SCENARIO...FLIGHT RESTRICTIONS ARE EXPECTED
DURING THE TAF VALID PERIOD DUE TO PERSIST FOG/DRIZZLE AND ALSO
PERIODS OF RAIN. IFR IS LIKELY WITH THE POTENTIAL FOR LIFR
PARTICULARLY TONIGHT. IFR IS LIKELY TO CONTINUE INTO WEDNESDAY AS
EVEN IF THE WEDGE STARTS TO ERODE PERIODS OF MODERATE TO HEAVY RAIN
WILL BRING POOR CONDITIONS. CAN/T RULE OUT THE POSSIBILITY OF LLWS
ON WEDNESDAY AS WELL WITH STRENGTHENING SOUTHERLY LOW LEVEL JET.

IFR OR LOWER CIGS REMAIN POSSIBLE INTO WEDNESDAY NIGHT UNTIL A COLD
FRONT PASSES AROUND MIDNIGHT. PRIOR TO THE FRONT...SHOWERS MAY
REDUCE VSBY AT TIMES AND LLWS MAY BE A CONCERN. THE FRONT WILL SHIFT
WINDS TO THE WEST AND GUSTS WILL INCREASE ABOVE 20 KT. SOME WESTERLY
WIND GUSTS UP TO 30 KT POSSIBLE THROUGH THURSDAY. WINDS DIMINISH
THURSDAY EVENING WITH HIGH PRESSURE/VFR TO FOLLOW.

&&

.MARINE...
HIGH PRESSURE EXTENDS FROM NEW ENGLAND INTO THE MID-ATLANTIC.
CURRENT WINDS ARE GENERALLY FROM THE NORTH...10 TO 15 KT DOWN THE
BAY. SHIFT TO THE SOUTH IS EXPECTED OCCUR TONIGHT INTO WEDNESDAY.
WINDS WILL INCREASE DURING THE AFTERNOON. BEST SOUTHERLY PUSH LOOKS
LIKE EVENING...BUT GUIDANCE SUGGESTS 20 KT OCCURRING UP THE BAY IN
THE AFTERNOON AND WILL RAISE SCA.

SCA CONDITIONS LIKELY TO CONTINUE THROUGH WEDNESDAY NIGHT. SHOWERS
WILL CONTINUE AND MAY MIX DOWN HIGHER GUSTS. A COLD FRONT WILL PASS
LATE AT NIGHT OR JUST AFTER DAYBREAK THURSDAY. SCA CONDITIONS WILL
CONTINUE AND SUSTAINED WINDS WILL INCREASE A BIT. MAY BE CLOSE TO
GALES...BUT FORECAST AT THIS TIME WILL KEEP IT JUST SHY. WILL DEPEND
ON HOW EFFECTIVE MIXING IS. HIGH PRESSURE WILL BUILD IN THURSDAY
NIGHT WITH LIGHTER WINDS THROUGH FRIDAY NIGHT. GUSTS MAY APPROACH
SCA CRITERIA SATURDAY AFTERNOON.

&&

.TIDES/COASTAL FLOODING...
WATER LEVELS WERE RUNNING 1/2 TO 3/4 FT ABOVE NORMAL. AS WINDS TURN
TO THE SOUTH BY WEDNESDAY...ANOMALIES ARE EXPECTED TO INCREASE. AM
NOT EXPECTING ANY MINOR TIDAL FLOODING ISSUES THROUGH WEDNESDAY
MORNING...BUT WILL HAVE TO WATCH TIDES WEDNESDAY AFTERNOON/EVENING
AS WATER LEVELS COULD GET CLOSE TO THOSE LEVELS IF ANOMALIES
INCREASE OVER 1 FT.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR MDZ003-
     501-502.
VA...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     VAZ025>031.
WV...FREEZING RAIN ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     WVZ050>053-055-501>504.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM TO 6 PM EST WEDNESDAY FOR
     ANZ530>534-537>543.

&&

$$
UPDATE...GMS
PREV DISCUSSION...BPP/ADS






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