FXUS61 KAKQ 110312
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
1012 PM EST THU DEC 10 2009
.SYNOPSIS...
COLD HIGH PRESSURE SLOWLY BUILDS INTO THE AREA OVERNIGHT AND
FRIDAY...AND BECOMES CENTERED ACROSS THE REGION FRIDAY NIGHT INTO
SATURDAY. THE HIGH MOVES OFF THE MID ATLANTIC COAST SATURDAY NIGHT. A
COUPLE WEAK LOW PRESSURE SYSTEMS...ONE OFF THE CAROLINA COAST AND
ONE MOVING THROUGH THE GREAT LAKES...WILL AFFECT THE AREA LATE
SATURDAY NIGHT AND SUNDAY. HIGH PRESSURE WITH MODERATING
TEMPERATURES ARRIVE FOR EARLY NEXT WEEK.
&&
.NEAR TERM /THROUGH FRIDAY NIGHT/...
ONLY CHANGES TO OVERNIGHT PERIOD WERE TO ADJUST CURRENT TEMPS AND
HRLY TRENDS.
PREV DISC...
THE BROAD POLAR LOW CONTINUES TO SPIN NEAR HUDSON
AND THE COLD ADVECTION CONTINUES AS THE FLOW TURNS MORE NORTHWEST
TONIGHT. THIS WILL CONTINUE TO PUSH COLDER AND DRIER AIR INTO THE
REGION. EXPECT THAT WINDS WILL CONTINUE TO BE GUSTY EARLY TONIGHT
AS THE GRADIENT REMAINS IN PLACE. BUT AS HIGH PRESSURE BUILDS IN
LATER/AFTER 3 AM THE GRADIENT SHOULD BEGIN TO RELAX A LITTLE...BUT
SHOULD NOT BE ENOUGH TO ALLOW DECOUPLING. SO FOR LOW TONIGHT HAVE
LEANED JUST A TOUCH ABOVE GUIDANCE.
HIGH PRESSURE THEN CONTINUES ITS EASTWARD MOVEMENT ON
FRIDAY...SETTLING OVER THE ARE BY FRIDAY NIGHT. THIS WILL KEEP THE
CLEAR SKY IN PLACE WITH LOTS OF SUNSHINE...BUT WARMING WILL BE
TOUGH AS 850 MB TEMP ARE AROUND -8C TO -10C. HAVE GONE WITH THE
COOLER MET WITH HIGHS IN THE UPPER 30S TO LOWER 40S. BUT COULD SEE
TEMPS STRUGGLING TO CLIMB THOSE VALUES. RADIATIVE CONDITIONS ARE
BETTER ON FRIDAY NIGHT...SO DESPITE SOME LIGHT WARM ADVECTION
BEGINNING..EXPECT FRIDAY NIGHT TO BE JUST AS COLD WITH READINGS IN
THE TEENS AND LOWER 20S.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY/...
THE AREA OF HIGH PRESSURE HANGS AROUND ON SATURDAY BUT THEN BEGINS
TO RETREAT NE ON SATURDAY NIGHT...LEAVING A WEDGE AREA OF DRY COOL
AIR IN PLACE. THE MODELS HAVE NOW ALL JUMPED TOWARD HAVING SYSTEMS
APPROACH LATE SATURDAY NIGHT AND MOVE THROUGH ON SUNDAY. AT THIS
POINT...IT LOOKS MAINLY LIKE A WARM ADVECTION/ISENTROPIC LIFT
SCENARIO AS ONE WEAK SHORTWAVE LIFTS ACROSS THE OHIO VALLEY AND A
WEAK SURFACE LOW FORMS ALONG THE CAROLINA COAST AND LIFTS NE
DURING THE DAY SUNDAY. AS THE MOISTURE OVER RUNS THE COLD DRY
AIRMASS IN PLACE...COULD EASILY SEE SOME WINTRY PCPN ON THE
LEADING EDGE...BUT IT SHOULD CHANGE TO RAIN PRETTY
QUICKLY...EXCEPT FOR FAR WESTERN PORTIONS OF CWA WHERE THE WEDGE
WILL HOLD LONGER. QPF AMOUNTS ARE NOT EXPECTED TO BE VERY
HIGH...BUT UP TO A HALF INCH IS POSSIBLE.
FOR TEMPERATURES...SHOULD BEGIN TO SEE THINGS MODERATE ON SATURDAY
AS 850 TEMPS CLIMB IN SW FLOW. BUT TIMING OF THE CLOUDS AND PCPN
SATURDAY NIGHT WILL HAVE A BIG IMPACT ON OVERNIGHT LOWS SATURDAY.
THE FASTER THEY ARRIVE THE LESS TEMPERATURES WILL FALL. FOR NOW
HAVE PLAYED A NON DIURNAL TRACE WITH READINGS DROPPING EARLY AND
THEN RISING AFTER MIDNIGHT. THIS TEMP TREND WILL IMPACT PCPN TYPE
GREATLY. WILL NEED TO CONTINUE TO MONITOR THIS AS A COLDER
SCENARIO COULD LEAD TO WINTRY WEATHER ISSUES.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
HV ALLOWED FOR A FEW REMNANT SHRAS SUNDAY NIGHT AS SFC LOW EXITS TO
THE NE AND SFC WEDGING STARTS TO BREAK DOWN. BY
MONDAY/TUESDAY...WNDS LOOK TO BACK FROM THE WNW TO THE SSW AHEAD OF
AN APPROACHING COLD FRONT FROM THE MS VLY/MIDWEST. NEW ECMWF HAS
COME INTO BETTER AGREEMENT WRT TIMING FRONTAL PASSAGE TUESDAY
MORNING...SO HV GONE WITH CHC POP ALL ZONES TUESDAY COINCIDENT WITH
FROPA...BUT WL STAY IN LOW CHC RANGE FOR NOW. TRANSITION TOWARDS A
MORE PRONOUNCED EAST COAST TROUGH INTO THE LATE WEEK PERIOD SHOULD
ALLOW FOR A COOLER END TO THE WEEK...WITH TEMPERATURES POTENTIALLY
FALLING TO ~ 0.5 TO 1 S.D. BELOW NORMAL VALUES LATE NEXT WEEK...INTO
THE U30S TO ARND 40 NW...INTO THE L/M 40S ACROSS SERN COUNTIES.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
NO MAJOR CHANGES IN STORE AS FCST LOOKS TO BE ON TRACK. HI PRES
OVER THE MID MS VLY WL MV EWD INTO THE MID ATLANTIC STATES KEEPING
VFR CONDS THROUGH FRI. EXPECT WSTRLY WNDS AROUND 10 KT KT TO
CONTINUE OVERNIGHT AT INLAND SITES. COULD SEE SOME GUSTS UP TO 20
KT AT CSTL SITES AS MIXING WL HELP TO BRING SOME WNDS ALOFT TO THE
SFC.
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 LOWER VSBYS/CIGS TO THE TAF SITES (MVFR TO POSSIBLY IFR)
BEGINNING ON SUN.
&&
.MARINE...
DECIDED TO RAISE GALES FOR THE NRN CSTL ZONES (N OF PARRAMORE) FOR
THE OVERNIGHT TIMEFRAME...AS COLDEST AIR AND SOMEWHAT HIGHER WINDS
IN 925-950MB LAYER HAVE NOT ARRIVED YET...AND WINDS ARE ALREADY
25 KT GUSTING TO 30 KT. (SCA CONDITIONS CONTINUE ACROSS THE
REMAINDER OF THE AREA WITH GUSTS TO ABOUT 30 KT EXPECTED).
WESTERLY FLOW CONTS FRI...AS SFC HIGH PRES BUILDS SETTLES OVER THE
WTRS FOR LT TOMORROW INTO SAT. SCA FLAGS SHOULD CONTINUE OVER
COASTAL WATERS FOR MUCH OF THE DAY ON FRI BEFORE GRADIENT RELAXES
AND SEAS SLOWLY SUBSIDE. ANOTHER PD OF INCREASED LLVL ONSHR WNDS ON SUN
AS WEAK SFC LOW PRES TRACKS BY JUST S OF THE WTRS.
TIDES...HAVE BEEN COMING DOWN W/ LAST CYCLE...ONLY ANOMALIES REMAINING
ARE OVER THE NRN BAY (AROUND 1 FOOT ABOVE NRML).
&&
.HYDROLOGY...
NO CHANGES TO PREVIOUS FCTS.
RUNOFF FROM TUESDAY AND WEDNESDAY'S RAINFALL IS NOW BEGINNING TO
WORK ITS WAY THROUGH THE HYDROLOGIC SYSTEM INTO THE LOWER PORTIONS
OF THE JAMES...APPOMATTOX AND CHOWAN AND LOWER ROANOKE BASINS.
MOST OF THE RIVERS HAVE CRESTED OR ARE CLOSE TO CREST AND SHOULD
BEGIN FALLING INTO THE MORNING HOURS OVER THE NEXT FEW DAYS. IN
VIRGINIA...NO FLOOD WARNINGS REMAIN ON THE APPOMATTOX RIVER.
HOWEVER...FLOOD WARNINGS CONTINUE FOR THE LOWER JAMES RIVER IN THE
RICHMOND METRO AREA....THE MEHERRIN NEAR LAWRENCEVILLE...THE LOWER
NOTTOWAY RIVERS AND THE BLACKWATER RIVER IN THE FRANKLIN VICINITY.
IN NORTHEAST NORTH CAROLINA....THE FLOOD WARNING CONTINUES FOR THE
CASHIE RIVER NEAR WINDSOR. OVERALL ALL AREA RIVERS WILL REMAIN AT
LEVELS ABOVE NORMAL OVER THE NEXT SEVERAL DAYS. FORECAST RAINFALL
OVER THE NEXT WEEK OR SO WILL HAVE SOME EFFECT ON THE RATE IN
WHICH THESE RIVERS FINALLY RECEDE TO NORMAL LEVELS.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
NC...NONE.
VA...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EST FRIDAY FOR ANZ630>633-654-
656-658.
GALE WARNING UNTIL 6 AM EST FRIDAY FOR ANZ650-652.
&&
$$
SYNOPSIS...LKB
NEAR TERM...ESS/LKB
SHORT TERM...ESS
LONG TERM...MAM
AVIATION...AM
MARINE...MAM/LKB/AM
HYDROLOGY...KLL
