FXUS61 KAKQ 100002
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
702 PM EST WED DEC 9 2009
.SYNOPSIS...
A STRONG AREA OF LOW PRESSURE OVER THE NORTHERN GREAT LAKES
HEADS INTO SOUTHEASTERN CANADA TONIGHT. THE ASSOCIATED COLD FRONT
PUSHES OFF THE MID ATLANTIC COAST BY THIS EVENING. HIGH PRESSURE
BUILDS BACK INTO THE AREA THURSDAY THROUGH SATURDAY. ANOTHER LOW
PRESSURE SYSTEM PASSES BY SOUTH OF THE MID ATLANTIC STATES ON
SUNDAY.
&&
.NEAR TERM /THROUGH THURSDAY/...
THE STRONG SURFACE LOW IS NOW OVER NRN LAKE HURON AND IS DOWN TO
ABOUT 973 MB. IT WILL CONTINUE TO LIFT OFF TO THE NE AND HEAD INTO
EASTERN CANADA. THE COLD FRONT ASSOCIATED WITH THIS LOW IS MOVING
ACROSS THE MOUNTAINS NOW AND SHOULD CONTINUE TO TRACK OFF TO THE
EAST...PASSING THROUGH THE AREA BETWEEN 00Z AND 4Z. AHEAD OF THE
FRONT...THE SKY HAS CLEARED IN MOST AREAS AND WITH THE DAY TIME
HEATING...THE MIXING HAS INCREASED...ALLOWING SOME OF THE WINDS
ALOFT TO MIX DOWN. WIND GUST HAVE INCREASED IN THE LAST FEW HOURS
INCREASING TO 30 TO 35 KTS IN THE EASTERN PARTS OF VA/NC AND MD.
THESE WINDS SHOULD CONTINUE FOR ANOTHER HOUR OR SO AND THEN BEGIN
TO WEAKEN AS THE MIXING BRIEFLY DECREASES. HOWEVER...ALONG AND
BEHIND THE FRONT THE WINDS COULD AGAIN GUST UP 35 KTS. THE WINDS
ALOFT IN THE MODELS ARE AROUND 45 KTS AT 925MB. THIS IS PROBABLY
NOT ENOUGH TO REACH THE 40 KT THRESHOLD FOR AN ADVISORY SO FOR NOW
WILL CONTINUE TO MENTION THE THREAT IN THE HWO. HOWEVER...IN THE
EASTERN COASTAL COUNTIES...THE MIXING SHOULD BE ENOUGH TO ALLOW
THE GUST TO REACH 40 KTS SO HAVE GONE WITH AN ADVISORY THROUGH MIDNIGHT.
FOR TEMPERATURES TONIGHT...HAVE GONE CLOSE TO THE MAV NUMBERS AS
IT WILL BE A PURE ADVECTION DROP NOT MUCH RADIATION GIVEN THE
STIRRING IN THE ATMOSPHERE.
THE SURFACE HIGH WILL BUILD INTO THE REGION ON THURSDAY...BUT WITH
THE FRONT HANGING UP IN THE COASTAL ZONES...SHOULD SEE SOME MID TO
HIGH LEVEL MOISTURE SLIDE OVER THE REGION...WITH THE GRADIENT FROM
SE TO NW. BUT WITH LITTLE TO NO LOW LEVEL MOISTURE...NOT EXPECTING
ANY PRECIP. FOR HIGHS IT WILL BE COOLER TOMORROW. HAVE LEANED
TOWARD THE MET NUMBERS FOR LOW AS TEMPERATURES WILL STRUGGLE TO
CLIMB WITH THE COLD ADVECTION.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
HIGH PRESSURE SITS OVER HEAD MOST OF THE PERIOD...AND WITH VERY
DRY AIR AROUND...SHOULD SEE LOTS OF CLEAR SKY AND COLD
TEMPERATURES. THE COLD ADVECTION CONTINUES ON THURSDAY NIGHT INTO
FRIDAY. BUT WITH LIGHT SFC WINDS THURSDAY NIGHT...RADIATIVE
CONDITIONS ARE MUCH BETTER SO SHOULD SEE TEMPERATURES
COOLER...SIMILAR TO THE MAV IN THE WEST AND MET IN THE EAST. ON
FRIDAY...THE SOUNDINGS SHOW THAT MIXING WILL BE LIMITED AND AS A
RESULT...MAY NOT EVEN MIX TO 850 MB. THIS COULD RESULT IN
TEMPERATURES IN THE 30S IN SOME AREAS. HAVE LEANED TOWARD THE
COOLER SIDE OF GUIDANCE AS SUNSHINE MAKES IT HARD TO HOLD VALUES
IN THE 30S. THE BIGGER NEW WILL BE THE DRYNESS OF THE AIR AS DEW
POINTS FALL INTO THE SINGLE DIGITS. NORMALLY THIS WOULD POSE A
FIRE WEATHER THREAT...BUT AS WET AS THE GROUND IS NOW...NOT
ANTICIPATING ANY FIRE WX ISSUES. THE COLD TREND CONTINUES ON
FRIDAY NIGHT WITH ANOTHER GOOD NIGHT OF RADIATIVE COOLING.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
LONG RANGE MODELS HAVE SLOWED TIMING OF NEXT SOUTHERN STREAM SYSTEM.
RECENT RUNS HAVE HINTED THAT NORTHERN FLOW MAY ACT TO SUPPRESS THIS
NEXT SYSTEM...WHICH THE 12Z EURO STRONGLY SUPPORTS. IN ANY CASE...IT
APPEARS THAT IT WILL AT LEAST SLOW DOWN IT DOWN TEMPORARILY. ALL
MODELS SHOW SURFACE HIGH PRESSURE SLOWLY RETREATING TO THE NE SAT
THROUGH EARLY SUN...WHILE A DEVELOPING SYSTEM OUT OF THE GULF STREAM
EJECTS NORTHEASTWARD ALONG THE SE COAST...LATER EDGED OUT TO SEA BY
THE NORTHERN STREAM LATE IN THE WEEKEND, OR EARLY NEXT
WEEK...DEPENDING ON THE MODEL.
SINCE THERE HAS NOT BEEN A LOT OF CONSISTENCY WITH MODELS...DID NOT
STRAY FAR FROM CURRENT CHANCE POPS. PERSISTENCE FORECAST FROM THE
LAST MONTH OR SO TELLS US THAT THIS SOUTHERN STREAM SYSTEM WILL WIN
OUT...AND POSSIBLY MOVE EVEN FARTHER NORTH ALONG THE MID ATLANTIC
SEABOARD BEFORE, MOVING OUT TO SEA...BUT WITH ALMOST ALL OF THE
MODELS SHOWING AT LEAST SOME SUPPRESSION THIS WEEKEND...DO NOT FEEL
CONFIDENT IN RAISING POPS...IF ANYTHING, IF TREND CONTINUES WE MAY
HAVE TO LOWER. WOULD LIKE TO SEE ONE MORE CYCLE OF RUNS BEFORE
OPTING TO GO THAT ROUTE.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR CONDS THIS EVNG ACRS THE AREA CONDS WL CONTINUE OVERNIGHT.
MAIN FCST PROBLEM CONTINUES TO BE WNDS OVER THE NEXT 24 HRS.
GENERALLY...SW/W WNDS AROUND 10 KTS INLAND AND 20 TO 25 KTS WITH
GUST 30 KTS ALONG THE CST WERE OBSERVED. COULD SEE SOME CROSSWIND
ISSUES AT RIC/SBY THROUGH MIDNIGHT BEFORE A MORE WRLY DIRECTION IS
ESTABLISHED. A COLD FNT CURRENTLY OVER WRN VA WL MV THROUGH THE
AREA THIS EVNG. COLD AIR BEHIND THE FNT WL HELP TO MIX WNDS ALOFT
DOWN TO THE SFC BY 06Z THU. DO NOT EXPECT GUSTS TO EXCEED 20 KTS.
GUSTS WL DIMINISH BY SUNRISE ONLY TO RETURN AGAIN MIDDAY THU.
HI PRES BLDS INTO THE MID ATLANTIC STATES THROUGH EARLY SAT. THE
NEXT IN A SERIES OF WEATHER SYSTEMS WL BRING A GOOD CHC OF PCPN
AND IFR CONDITIONS TO THE TAF SITES BEGINNING LATE SAT INTO SUN.
&&
.MARINE...
COLD FRONT WILL CROSS THE WATERS AROUND 00Z THIS EVENING. LOOK FOR
GUSTY WINDS TO PICK UP AS THE GRADIENT INCREASES AHEAD OF AND ALONG
THE FRONT...THEN CAA BEGIN POST FROPA LATE. RE-ISSUED GALE FOR
MIDDLE CHES BAY BASED ON OBS UPSTREAM. GALES SHUD BE REPLACED BY
STRNG SCA'S ACROSS THE CHES BAY AND CURRITUCK SND AREAS EARLY SUN
MORNING.
WESTERLY FLOW CONTS INTO FRI B4 SFC HIGH PRES BUILDS OVR WTRS FOR LT
FRI INTO SAT. SCA ALONG CSTL WTRS FOR SEAS WILL LIKELY CONT INTO FRI
AS WELL. ANOTHER PD OF INCRSD LLVL ONSHR WNDS XPCTD LT SAT INTO SUN
AS NEXT SFC LOW PRES TRACKS BY JUST S OF THE WTRS.
&&
.HYDROLOGY...
THE OVERNIGHT MODERATE TO HEAVY RAIN...IN COMBINATION WITH
WELL-SATURATED SOILS HAVE PRODUCED SHARP RISES ALONG MOST OF THE
RIVERS AND STREAMS ACROSS THE HSA. RIVER FLOOD WARNINGS ARE NOW IN
EFFECT FOR THE LOWER JAMES RIVER AT RICHMOND-WESTHAM AND
RICHMOND-LOCKS...AS WELL AS THE MEHERRIN RIVER NEAR LAWRENCEVILLE IN
BRUNSWICK COUNTY. AT THESE GAGES...FLOOD STAGES ARE EXPECTED TO BE
REACHED EARLY ON THURSDAY. RIVER FLOOD WARNINGS CONTINUE ALONG THE
NOTTOWAY RIVER NEAR SEBRELL IN SOUTHAMPTON COUNTY. LOCATIONS THAT
WILL BE MONITORED CLOSELY ARE ALONG THE APPOMATTOX RIVER AT
FARMVILLE AS WELL AS MATTOAX IN AMELIA COUNTY. OTHER AREAS ARE
EXPECTED TO REMAIN BETWEEN ONE-HALF AND THREE-QUARTERS BANKFULL OVER
THE NEXT FEW DAYS AS THE RUNOFF MOVES THROUGH THE BASINS. IT IS
IMPORTANT TO NOTE THAT FLASH FLOOD GUIDANCE VALUES ARE NOW
REFLECTING THE WET CONDITIONS...THEREFORE ANY RAINFALL EVENT DURING
THE NEXT WEEK THAT PRODUCES ONE TO 2 INCHES IN ONE TO SIX HOURS
COULD AT LEAST PRODUCE NUISANCE FLOOD PROBLEMS IN SOME AREAS.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR MDZ024-025.
NC...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ017-102.
VA...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR VAZ095-098>100.
MARINE...GALE WARNING UNTIL 1 AM EST THURSDAY FOR ANZ630>633.
GALE WARNING UNTIL 8 AM EST THURSDAY FOR ANZ650-652-654-656-
658.
&&
$$
SYNOPSIS...ESS
NEAR TERM...ESS
SHORT TERM...ESS
LONG TERM...SMF
AVIATION...AM
MARINE...SMF
HYDROLOGY...KLL
