-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KAKQ 041551
AFDAKQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
1051 AM EST WED MAR 4 2015

.SYNOPSIS...
A WARM FRONT LINGERS OVER THE NORTHERN MID ATLANTIC THIS MORNING...WITH
A COLD FRONT SLOWLY CROSSING THE REGION LATER THIS AFTERNOON
THROUGH TONIGHT. THE FRONT WILL STALL OVER NORTH CAROLINA ON
THURSDAY...WITH A WAVE OF LOW PRESSURE MOVING ALONG THE FRONT INTO
THURSDAY NIGHT. THIS WILL BRING ANOTHER ROUND OF WINTRY WEATHER TO
THE AREA...FOLLOWED BY COLD AND DRY CONDITIONS BY FRIDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
QUICK UPDATE TO REFLECT ISSUANCE OF WINTER STORM WATCH OVER
WICOMICO/DORCHESTER COUNTIES IN MARYLAND. INCOMING 12Z GUIDANCE
BOLSTERING FORECAST CONFIDENCE OF THE GOING FORECAST...OUTLINED
IN THE SHORT TERM SECTION BELOW. FORECAST CONFIDENCE FOR WINTER
STORM HEADLINES IS SUFFICIENT TO JUSTIFY WATCH OVER THESE AREAS.
WILL MAKE ADVISORY/WARNING DECISIONS THIS AFTN AS 12Z DATA
CONTINUES TO FILTER IN.

PREVIOUS DISCUSSION SENT 706 AM EST...
THE CURRENT SURFACE ANALYSIS SHOWS A QUASI-STATIONARY FRONTAL
BOUNDARY LINGERING FROM THE TENNESSEE VALLEY THROUGH THE NRN MID-
ATLANTIC WITH A RESIDUAL WEDGE AIRMASS IN PLACE TO THE LEE OF THE
MOUNTAINS. THE FRONTAL BOUNDARY IS SITUATED IN BETWEEN ARCTIC HIGH
PRESSURE BUILDING OVER THE CENTRAL PLAINS AND HIGH PRESSURE OFF
THE COAST...AND IS ALIGNED NEARLY PARALLEL TO THE UPPER LEVEL FLOW
AND HENCE IT WILL MOVE VERY LITTLE TODAY. STRATUS WILL LINGER
THROUGH AT LEAST MID- MORNING...WITH AREAS OF FOG
EARLY...ESPECIALLY OVER SE VA/NE NC. HIGH TEMPERATURES WILL BE
VERY CHALLENGING TODAY. THERE IS A POTENTIAL THAT FAR NRN PORTIONS
STAY IN THE UPPER 40S...WITH LOW 70S ACROSS SRN PORTIONS. CENTRAL
PORTIONS COULD EXPERIENCE A SPREAD OF AT LEAST 10-15F DEPENDING ON
THE EVENTUAL POSITION OF THE FRONTAL BOUNDARY. THE HIGHEST POPS
TODAY WILL BE ACROSS THE FAR NRN TIER COUNTIES IN CLOSER PROXIMITY
TO THE BOUNDARY...WITH A SHARP GRADIENT ACROSS CENTRAL PORTIONS
THAT TAPERS TO 10-20% ACROSS S/SE PORTIONS.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
A COLD FRONT PRESENTLY BACK OVER THE OHIO VALLEY DROPS INTO THE AREA
THIS EVENING AND TRACKS NNW-SSE ACROSS THE AREA OVERNIGHT INTO THU
MORNING. MEANWHILE...A WAVE OF LOW PRESSURE DEVELOPS ALONG THE FRONT
AND TRACKS ACROSS THE CAROLINAS WEDNESDAY NIGHT INTO THURSDAY. MUCH
COLDER AIR ARRIVES BEHIND THE FRONT WITH MOST OF THE AREA FALLING
INTO THE UPPER 20S/LOW 30S BY THU AFTN. FORECAST SOUNDINGS SHOW DRY
AIR LINGERING BETWEEN 600-400MB TONIGHT...SO ANY PCPN (IN THE FORM
OF -RA) WILL BE LIGHT. A STRONG ANTI-CYCLONIC JET IS PRESENTLY
LOCATED FROM THE MID-MISSISSIPPI VALLEY THROUGH ATLANTIC CANADA.
THIS JET STRUCTURE WILL TRANSLATE EWD THROUGH THU AS A STRONG TROUGH
DIGS ACROSS THE UPPER MIDWEST AND GREAT LAKES BY LATER THU MORNING
INTO THU AFTERNOON. IT IS AT THIS TIME THAT DEEPER MOISTURE WILL
ARRIVE AND RRQ FORCING WILL BE IDEALIZED AND TRIGGER THE ONSET OF
WINTRY PCPN FROM NW-SE ACROSS THE AREA.

IT IS NOT UNTIL 21Z THU TO 00Z FRI THAT SUB 1540M 850-700MB
THICKNESS VALUES ARRIVE INTO NW PORTIONS OF THE AREA. HOWEVER...BY
THIS TIME THE STRONGEST UVM WILL BE EXITING THE COAST. OVERALL IT
APPEARS THAT SLR VALUES WILL BE LOW (PERHAPS 5:1-8:1) GIVEN THAT
THERE WILL BE A PERIOD OF SLEET...AND THAT MID-LEVEL THICKNESSES
WILL BE `WARM` DURING THE STRONGEST FORCING. THE CURRENT FORECAST
HAS A NARROW BAND OF 3-4" FROM LOUISA COUNTY TO DORCHESTER COUNTY
BORDERED BY A BAND OF 2-3" FOR OTHER PORTIONS OF THE NW
PIEDMONT...NRN NECK...AND LOWER MD EASTERN SHORE. CURRENTLY 1-2" IS
FORECAST FROM THE RIC METRO DOWN THROUGH HAMPTON ROADS...WITH 1" OR
LESS FARTHER S. A BRIEF PERIOD OF FZRA IS POSSIBLE DURING THE
TRANSITION FROM RA TO SN/IP WITH ANY ICE ACCUM ONLY TRACE TO A FEW
HUNDREDTHS OF AN INCH. CONFIDENCE IS NOT HIGH ENOUGH FOR A WATCH
ACROSS THE FAR N AT THIS TIME GIVEN THAT THIS IS A LATER THIRD
PERIOD EVENT...SO THIS WILL CONTINUED TO BE HIGHLIGHTED IN THE HWO.

WINTRY PCPN SHOULD TAPER OFF THU EVENING...WITH DRIER AIR ARRIVING
FROM THE NW DURING THE LATE EVENING. TEMPERATURES WILL CONTINUE TO
PLUMMET WITH LOWS FRI MORNING RANGING FROM THE LOW TEENS NW...TO LOW
20S SE. HIGHS FRI WILL STRUGGLE TO REACH 30-35 FRI UNDER A MOSTLY
SUNNY SKY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
EXTENDED PERIOD WILL BE HIGHLIGHTED BY GENERALLY DRY CONDITIONS
AND A RETURN TO NEAR SEASONABLE NORMAL TEMPS.

MEDIUM RANGE GUIDANCE IN GENERAL CONSENSUS WITH THE UPPER FLOW
THRU THE EXTENDED...CHARACTERIZED BY RIDGING/BLOCKING OVER THE WRN
CONUS/ERN PACIFIC AND BROAD TROUGHING OVER THE CNTRL AND ERN
CONUS. TO BEGIN THE PERIOD...COLD/DRY 1030+MB ARCTIC HIGH PRESSURE
CENTERS OVER THE MID-ATLANTIC REGION. THURSDAYS COLD FRONT LOCATES
OFF THE COAST...EXTENDING SWWD INTO THE NRN GULF. H85 TEMPS DROP
TO AROUND -8C FRI (~-1 STD DEV)...SLIGHTLY WARMER THAN DEPICTED 24
HRS AGO. HIGHS FRI GENERALLY IN THE LOW-MID 30S INLAND AND UPPER
20S-LOW 30S COASTAL AREAS. AIRMASS MODIFIES FRI NIGHT-SAT AS THE
COLD/DRY AIR RETREATS NWD. HIGH PRESSURE REMAINS OVER THE REGION
SAT...WITH LIGHT RETURN FLOW HELPING TO MODERATE LOW LEVEL
THICKNESSES. TEMPS WARM INTO THE UPPER 40S-LOW 50S INLAND AND LOW-
MID 40S COASTAL AREAS. SKY AVG MOSTLY SUNNY-PARTLY CLOUDY. HIGH
PRESSURE REMAINS OVER THE REGION SUN...RESULTING IN CONTINUED DRY
AND WARMING CONDITIONS. HIGHS IN THE LOW-MID 50S INLAND AND LOW
40S TO UPPER 40S COASTAL AREAS. ATTENTION THEN TURNS OUT
WEST...WHERE MODELS CONTINUE TO STRUGGLE HANDLING SPLIT/BLOCKY
FLOW AND SRN STREAM ENERGY OVER THE DESERT SW/BAJA. GOOD NEWS IS
THAT NOW THE DETERMINISTIC ECMWF HAS TRENDED DRY SUN NIGHT-EARLY
NEXT WEEK...MATCHING THE GFS AND ENSEMBLES. HOWEVER...SPLIT FLOW
CONTINUES RESULTING IN LOW CONFIDENCE EARLY NEXT WEEK. FRONT OVER
THE GULF WILL ATTEMPT TO AMPLIFY AND LIFT NWD AS SRN STREAM ENERGY
APPROACHES...BUT WILL KEEP POPS SILENT. HIGHS EARLY NEXT WEEK (MON
AND TUES) CONTINUE TO WARM INTO THE MID 50S INLAND AND LOW-UPPER
40S COASTAL AREAS THANKS TO COLD WATER.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
AS OF 12Z...IFR/LIFR CONDS ARE FOUND THROUGHOUT THE AREA WITH A
WARM FRNT IN THE VICINITY AND VERY MOIST LO LEVELS. THE CHANCE OF
-RA HAS DIMINISHED THIS MORNG BUT THERE IS STILL SOME AREAS OF
-DZ. SW WINDS GUSTING UP TO 20-25 KT WILL CONTINUE TDA AHEAD OF
AN APPROACHING COLD FRNT. SOME IMPROVEMENT IN CIGS IS EXPECTED
THIS AFTN AT MOST TAF SITES...BUT IFR/MVFR IS STILL PSBL. THE COLD
FRNT DROPS INTO THE AREA THIS EVENG INTO TNGT...WITH RAIN AND
LIFR/IFR CONDS EXPECTED. DURING THE DAY THU...THE PCPN BECOMES SNOW
NRN PORTIONS AND MIXED PCPN SRN PORTIONS. PCPN BECOMES MAINLY SNOW
THU EVENING BEFORE ENDING FROM THE NW. ANY SNOW ACCUMULATIONS ARE
EXPECTED TO BE AROUND 1-3 IN ON AVG...WITH PSBLY MORE AT KSBY. A
GUSTY NORTHERLY WIND WILL DEVELOP ALONG THE COAST THU. HIGH PRESSURE
THEN BUILDS IN WITH DRY WEATHER FRIDAY THROUGH SUNDAY.

&&

.MARINE...
HAVE EXTENDED DENSE FOG ADVISORIES NWD TO INCLUDE THE ENTIRE
BAY...ERN VA RIVES AND COASTAL WATERS TO CHINCOTEAGUE AS WAA
OVERSPREADS COLD WATERS. WAA WILL WANE THROUGH THE
AFTERNOON...ALLOWING VISIBILITIES TO IMPROVE. MAY NEED TO EXTEND
THE DENSE FOG HEADLINES WITH THE NEXT UPDATE. SW WINDS HAVE
DIMINISHED THIS MORNING AS THE STRONGEST GRADIENT WINDS PUSH
OFFSHORE. SEAS HAVE SUBSIDED BELOW 5 FT EXCEPT IN THE SRN COASTAL
WATERS WHERE SE SWELL HAS HELPED MAINTAIN SCA CONDITIONS. HAVE
OPTED TO ISSUE SCA HEADLINES SOUTH OF CAPE CHARLES LIGHT FOR
TODAY...AS SEAS WILL REMAIN 4-5 FT.

.PREV DISCUSSION...
A COLD FRNT APPROACHES FM THE W TDA WITH S/SW FLOW CONTINUING OUT
AHEAD OF THE FRNT. WINDS MAY COME CLOSE TO SCA THRESHOLDS THIS MORNG
OVER THE LWR BAY DUE TO A STRONG LLJ...BUT WAA AND COLD WATERS WILL
CAUSE A SHARP INVERSION THAT SHOULD KEEP SUSTAINED WINDS UP TO ~15
KT THERE. ISSUED A DENSE FOG ADVSRY FOR CSTL WTRS S OF CAPE CHARLES
LIGHT DUE TO EXPECTED VSBYS AOB 1 MI THRU THE MIDDAY HRS IN
ASSOCIATION WITH VERY MOIST LO LEVELS. THE FRNT SLOWLY DROPS THRU
THE AREA LATE TDA INTO TNGT AS A WAVE OF LO PRES DEVELOPS ALONG THE
FRNT. AS THE FRNT FINALLY PUSHES S OF THE AREA TNGT...SCA CONDS WILL
COMMENCE OVR THE WTRS. THESE CONDS WILL CONTINUE INTO THU NGT AS
WELL SO EXTENDED THE HEADLINES INTO THE 4TH PERIOD. WINDS MAY COME
CLOSE TO GALE FORCE OVR SRN CSTL WTRS BUT CONFIDENCE IS NOT HI ENUF
TO ISSUE A GALE WATCH/WARNG ATTM. ALSO KEPT ALL RIVER ZONES EXCEPT
THE LWR JAMES OUT OF THE ADVSRY FOR NOW BUT WILL CONTINUE TO
MONITOR. WAVES OVER THE BAY UP TO 4-5 FT WITH SEAS OVER CSTL WTRS UP
TO 7-8 FT. SFC HI PRES THEN BLDS IN FOR FRI INTO THE WEEKEND LEADING
TO IMPROVING MARINE CONDS.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY EVENING
     FOR MDZ021-022.
NC...NONE.
VA...NONE.
MARINE...DENSE FOG ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
     ANZ630>638-652-654-656-658.
     SMALL CRAFT ADVISORY FROM 4 AM THURSDAY TO 4 AM EST FRIDAY FOR
     ANZ630>632-634-650-652-654.
     SMALL CRAFT ADVISORY FROM 7 AM THURSDAY TO 4 AM EST FRIDAY FOR
     ANZ633-638.
     SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR ANZ656-658.

&&

$$
SYNOPSIS...AJZ/LKB
NEAR TERM...AJZ/MAM
SHORT TERM...AJZ
LONG TERM...SAM
AVIATION...MAS
MARINE...MAS/SAM