FXUS61 KAKQ 051201
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
701 AM EST SAT DEC 5 2009
.SYNOPSIS...
LOW PRESSURE WILL STRENGTHEN OFF THE COASTAL CAROLINAS THIS
MORNING...AND TRACK NORTHEAST OFF THE VIRGINIA CAPES LATER THIS
AFTERNOON AND EVENING. THE STORM MOVES QUICKLY AWAY FROM THE
REGION TONIGHT...AS HIGH PRESSURE BUILDS BACK IN FROM THE WEST SUNDAY
INTO MONDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
UPDATE TO MAKE SOME MINOR ADJUSTMENTS TO THE FCST IN THE NEAR
TERM...TRENDS CONTINUE TO SHOW TEMPERATURES VERIFYING A FEW
DEGREES WARMER THAN ALL GDNC...AND HAVE REMOVED ANY MENTION OF
SNOW (EVEN A MIX) FOR THE ENTIRE MRNG. HAVE ALSO SCALED BACK ON
SNOW ACCUMULATIONS UNTIL AFTER 4PM OR SO AS COLDER AIR LOOKS
DELAYED 1-2 HRS. ALL IN ALL...DOUBT WE'LL SEE ANYTHING MORE THAN
1" ANYWHERE IN THE CWA UNTIL AFTER DARK...AND AT THAT PT DRY AIR
MAY BE MOVING IN BEFORE IT GETS COLD ENOUGH...HAVE 1-2 INCHES AT
MOST FOR ALL AREAS.
RAIN BEGINNING TO OVERSPREAD THE ENTIRE CWA ERLY THIS MRNG...AS
WARM CONVEYOR BELT FEATURES CAN BE SEEN WELL ON IR SATL...MSTR
FEED FROM NRN FLORIDA/ERN GULF OF MEXICO ALL THE WAY UP THE
EASTERN SEABOARD. SFC TEMPERATURES IN OUR NECK OF THE WOODS
RUNNING RATHER MILD RIGHT NOW...LWR/MID 50S OVER HAMPTON ROADS AND
NE NC...WITH MID 40S METRO RICHMOND...AND LWR 40S OVER THE NW
PIEDMONT. MORE IMPORTANTLY...THE SFC DEW PTS HAVE RISEN AS
WELL...EVEN CHO HAS A DEW PT OF 36 F SO EVAPORATIVE COLUMN COOLING
PROCESSES WILL NOT BE A FACTOR THROUGH MOST OR ALL OF THE MRNG
HRS. GFS/NAM/SREF IN PRETTY GOOD AGREEMENT THAT WET BULB ZERO HGTS
REMAIN AT OR ABOVE 1 K FT CWA WIDE THROUGH 17-18Z...THEREFORE HAVE
SLOWED DOWN THE CHANGEOVER/MIX TO SNOW THIS MORNING...EVEN ACRS
THE PIEDMNT (ALTHOUGH WILL KEEP WSW HEADLINE START TIME AS IS).
WHAT WE NEED FOR APPRECIABLE SNOW OVER THE AKQ CWA CAN BE SEEN ON
ON THE ENHANCED WV SATL...CURRENTLY ACRS KENTUCKY AND CNTRL/ERN
TENNESSEE. THIS REGION COINCIDES WELL W/ MODEL LOW LVL
FRONTOGENESIS (850-700 MB) AND UPR LEVEL Q-VECTOR CONV
(500-300MB). AS UPR SYSTEM AMPLIFIES LATER THIS AFTN...ESP AFTER
21Z...THE STRG DYNAMICS SHOULD AID IN THE DEVELOPMENT OF A BAND OF
HEAVIER PRECIP ACRS NRN PORTIONS OF THE CWA. AT 21Z...MODEL LOW LVL
THICKNESS (1000-850MB) AND BUFR SNDG PROFILES CONTINUE TO SUPPORT MAINLY RAIN
AS PTYPE FOR ALL EXCEPT FAR NW PORTIONS OF THE CWA...BUT WITH THAT
AREA OF STRG LIFT PROGGED TO MOVE IN...SHOULD SEE PRECIP
CHANGEOVER TO MAINLY SNOW ALONG FOR WRN PORTIONS OF
GOOCHLAND/CUMBERLAND/FLUVANNA/LOUISA. LIFT AND UPR SUPPORT LOOKS
OPTIMAL BETWEEN 22Z AND 02Z OVER NRN PIEDMNT/CNTRL VA ZONES...ABOUT 1-2
HRS LATER OVER THE NRN NECK AND MD ERN SHORE. HAVE DECIDED TO ADD
CUMBERLAND/GOOCHLAND TO THE ADVSY TO COVER FAR WRN PORTIONS OF
THESE CNTYS (EVEN THOUGH THE SLIGHTLY WARMER ERN PORTIONS LIKELY
SEE < 1" OF SNOW TOTAL). FARTHER SOUTH AND EAST...HAVE A BUFFER OF
SNOW ACCUMULATIONS UP TO 1" (I.E. CAROLINE/HANOVER/NRN NECK AND
DORCHESTER MD).
DEPENDING ON THE AMT OF AMPLIFICATION OF THE UPR DYNAMICS...NRN
PORTIONS OF THE NRN NECK/DORCHESTER MD WILL NEED TO BE MONITORED
ERLY THIS EVENING IN CASE COLD AIR COMES IN FASTER THAN
ANTICIPATED...WHICH COULD ALLOW FOR A QUICK BURST OF HEAVIER SNOW
THAT WOULD NEED AN ADVSY. OTHERWISE...EXPECT RAPID DISSIPATION TO
SNOW SHWRS FROM SW TO NE LATER THIS EVENING AS MUCH DRIER AIR
MOVES IN FROM THE WSW. LOWS OVERNIGHT IN THE MID 20S ACRS THE
PIEDMNT...LWR/MID 30S AT THE COAST.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY/...
HI PRES BUILDS OVR THE FA SUN...BRINGING DRY BUT COLD CNDTNS.
LWRD MAX TMPS ABT A CATEGORY FOR NRN ZONES WHERE SOME SNOW MAY
INITIALLY BE ON THE GRND...RAISED THEM A BIT HIGHER ELSEWHERE. HIGHS
40-45 N...MID/UPR 40S CNTRL AND SOUTH. CLDS FROM NXT SRN STREAM
S/W APPRCH LATE SUN NITE. LOWS M20S-M30S. NOT MUCH MSTR FOR THE
S/W TO WORK WITH ON MONDAY...SO WILL KEEP IT DRY BUT M CLDY. HIGHS
M40S- L50S.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
GENERAL MODEL AGREEMENT IN THE EXTENDED RANGE CONTINUES AS THE MODELS
SHOW A FAST FLOW ACROSS THE US WITH MUCH MORE PACIFIC FLOW VERSUS
A MERIDIONAL FLOW. THIS WILL RESULT IN RELATIVELY MILD WEATHER FOR
THIS TIME OF YEAR...BUT WILL SEE SEVERAL SYSTEMS MOVING ACROSS THE
US WITH GULF MOISTURE AVAILABLE.
TO BEGIN THE PERIOD...AS NORTHERN STREAM ENERGY RACES OUT OF THE
NORTHERN PLAINS INTO NEW ENGLAND TO BEGIN THE PERIOD...QUASI ZONAL
FLOW ALOFT SHOULD ALLOW FOR A GENERALLY DRY FIRST HALF OF THE
UPCOMING WEEK. DID ALLOW FOR A QUICK SLIGHT CHC POP MONDAY NGT IN
ASSN WITH A QUICK MOVING SOUTHERN STREAM S/W. OTW...MAINLY DRY
TIMEFRAME FOR MONDAY NIGHT/TUESDAY
BY LTR TUESDAY/WEDNESDAY...DEEP LOW PRESSURE EMERGES FROM THE
CENTRAL ROCKIES AND PUSHES ACROSS THE CENTRAL/SOUTHERN PLAINS...AND
EVENTUALLY PUSHING NE INTO THE EASTERN GRT LKS/NEW ENGLAND BY LATE
IN THE PERIOD. THIS WL TURN FLOW ALOFT MORE SW DOWNSTREAM ACROSS THE
EASTERN CONUS...ALLOWING BUILDING MOISTURE/CLOUDS LTR TUESDAY...WITH
INCREASED CHCS FOR OVERRUNNING RAIN ON TUESDAY NIGHT INTO WEDNESDAY.
THE GFS AND ECMWF BOTH SHOW A STRONG TROUGH SWEEPING EAST WITH THIS
SYSTEM ON WEDNESDAY. THE GFS IS MORE AMPLIFIED AND AS A RESULT
PUSHES MUCH WARMER AIR INTO THE REGION WEDNESDAY. THE ECMWF IS NOT
AS AGGRESSIVE...NOT AMPLIFYING THE WAVE UNTIL AFTER IT REACHES NEW
ENGLAND SO THE WARMING IS NOT A GREAT. FOR NOW HAVE CONTINUED TREND
TO INCREASE POPS TO HIGH CHANCE AND HELD TEMPERATURES DOWN CLOSER TO
THE ECMWF/HPC NUMBERS. AS PREV SHIFT NOTED...IF THE PATTERN DOES
AMPLIFY AS QUICKLY AS THE GFS DEPICTS...IT COULD EASILY ALLOW
TEMPERATURES TO PUSH INTO THE 60S PRIOR TO THE COLD FRONTAL PASSAGE.
BY THURSDAY...THE LOW IS DEEPENING OFF THE NEW ENGLAND COAST WITH
A COLD NW FLOW ACROSS THE MID ATLANTIC STATES. THIS SHOULD ALLOW
FOR CLEARING CONDITIONS WITH COOL...BUT NOT COLD TEMPERATURES.
&&
.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
RADAR SHOWS MORE PRECIP DEVELOPING ACROSS THE CWA. EXPECT CIGS TO
DROP INTO IFR CONDS BEFORE SUNRISE OVER SE VA AND NE NC AS LOW
CEILINGS MOVE IN. WNDS WILL INCREASE ALONG COASTL SECTIONS AS LOW
MOVES OFF COAST OF NC WITH GUSTS TO AROUND 25 KT PSBL. CIGS WILL
GENLY LOWER TO IFR CONDS DURING THE MORNING AS RAIN INCREASES. A
CHANGEOVER FROM RAIN TO RAIN/SNOW MIXED EXPECTED TO OCCUR BY LATE
AFTN INTO EVENING HRS FROM RIC TO SBY. AREAS CLOSEST TO COAST
LIKELY TO REMAIN MOSTLY RAIN ALTHOUGH SLIGHT CHC OF RAIN/SNOW
MIXED STILL PSBL AROUND SUNSET. CLEARING LATE SAT NIGHT/SUN AM AS
LOW MOVES FARTHER NORTH AND HI PRES BUILD IN FOR SUN. THE NEXT
SIGNIFICANT CHC OF PCPN LOOKS TO BE WED.
&&
.MARINE...
ALL MODELS AGREE ON DEVELOPING LOW OFF THE CAROLINA COAST TODAY.
TIMING OF INCREASE IN WINDS WITH THIS DEVELOPMENT SYSTEM WILL
FOLLOW SREF GUIDANCE. LOOKING AT THE 925 MB LEVEL SEE THE MAIN
INCREASE IN WINDS DEVELOPING THIS AFTERNOON AND TONIGHT. THIS
MEANS THE STRONGEST WINDS WILL DEVELOP WHEN THE WINDS TURN MORE
NORTHERLY TO NORTHWEST. SREF GUIDANCE TONIGHT SHOWS HIGH
PROBABILITY OF SCA WINDS OVER ALL WATERS BUT KEYS IN ON NE COASTAL
WATERS FOR THE BEST CHANCE OF GALE. MAIN THREAT OF GALE WILL BE
FROM WIND GUSTS. USED A GUST FACTOR OVER ATER BETWEEN 1.2 AND 1.3.
THIS CORRESPONDS TO RESEARCH PRESENTED AT THE NWA MEETING. THIS
JUST BARELY BRINGS GALES TO NRN WATERS. BY LATE TONIGHT AND INTO
SUN AS HIGH PRESSURE MOVES IN WINDS WILL QUICKLY SUBSIDE BELOW SCA.
WINDS TURN MORE TO THE NNW LTR TONIGHT/ERY SUN...SO SEAS/TIDAL
ANOMALIES DO NOT HAVE A LOT OF TIME TO BUILD (ALTHOUGH SEAS OF AT
LEAST 7-9 FT ARE STILL EXPECTED). HV HELD OFF ON HIGH SURF
ADVISORY FOR NOW.
HIGH PRESSURE BUILDS IN LATER SUNDAY/MONDAY ALLOWING SEAS/WINDS TO
SUBSIDE....WITH MORE BENIGN CONDITIONS ACROSS THE WATERS FOR THE
FIRST HALF OF NEXT WEEK.
&&
.HYDROLOGY...
DUE TO RECENT HEAVY RAINFALL OVER THE REGION...FLOOD WARNINGS
CONTINUE FOR THE MEHERRIN RIVER AT LAWRENCEVILLE AND THE NOTTOWAY
RIVER NEAR STONY CREEK. MAY NEED TO ISSUE A WRNG FOR SEBRELL LATER
TODAY. SEE LATEST WBCFLSAKQ FOR MORE INFO.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...WINTER WEATHER ADVISORY FROM NOON TODAY TO 10 PM EST THIS
EVENING FOR VAZ048-049-061-062.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST SUNDAY FOR ANZ630>633-656-
658.
GALE WARNING UNTIL 5 AM EST SUNDAY FOR ANZ650-652-654.
&&
$$
SYNOPSIS...LKB
NEAR TERM...LKB
SHORT TERM...LKB/MPR
LONG TERM...MAM
AVIATION...JAB
MARINE...JAB
HYDROLOGY...JAB
