FXUS61 KAKQ 081305
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
805 AM EST TUE DEC 8 2009
.SYNOPSIS...
HIGH PRESSURE ACROSS THE MID ATLANTIC REGION EARLY TODAY WILL
RETREAT INTO NEW ENGLAND AND THE CANADIAN MARITIMES TONIGHT.
WEAK LOW PRESSURE WILL TRACK NORTHEAST ALONG THE ATLANTIC
SEABOARD WEDNESDAY...WHILE A MORE INTENSE LOW PRESSURE SYSTEM
TRACKS ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. A COLD
FRONT WILL THEN PUSH OFF THE MID ATLANTIC COAST BY LATE WEDNESDAY
NIGHT...AS HIGH PRESSURE BUILDS BACK INTO THE AREA THURSDAY AND
FRIDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE TO ISSUE FLOOD WATCH FOR TONIGHT UNTIL NOON WED. PREVIOUS
DISCUSSION FOLLOWS.
SFC HIGH PRES QUICKLY RETREATS TO NEW ENGLAND WHILE MSTR
INCREASES OUT OF THE SW...AS YET ANOTHER SYSTEM HEADS TOWARD THE
REGION. MDL TRENDS CONTINUE TO FAVOR A SPLIT FLOW SOLN...WITH ONE
(MORE INTENSE) LOW SHIFTING THRU THE GREAT LAKES AND ANOTHER LOW
MOVING NE ALONG THE ATLC COAST THRU EARLY THU. DID NOT STRAY FAR
FROM CURRENT POPS...WHICH INCREASE (FROM W TO E) TO 100% LATER
THIS EVENING AND OVERNIGHT.
FCST SOUNDINGS AND LLVL THICKNESSES SUPPORT A RAIN EVENT ACROSS
THE FCST REGION...AS THE LLVL CAD WEDGE WEAKENS/BECOMES MORE
SHALLOW WITH TIME AS THE FLOW VEERS E AND EVENTUALLY SE. HOWEVER...
MAX WET BULB TEMPS ALOFT BTWN -0 AND -3C LATER THIS AFTN/EARLY
EVE DO SUPPORT THE POSSIBILITY OF SOME LIGHT ICE PELLETS MIXING IN
EARLY ON (AT THE ONSET) AS THE COLUMN COOLS DIABATICALLY THROUGH
EVAPORATION. DO NOT EXPECT MORE THAN A TRACE OF WINTRY PRECIP
HWVR...AS WARM/MOIST SURGE AT LLVLS WILL PUT A QUICK END TO EVAP
COOLING POTENTIAL...AS DWPTS/WET BULB TEMPS CLIMB QUICKLY AFTER 00Z.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
SHORT TERM MODELS ARE ONCE AGAIN CONSISTENT WITH THE BROAD SCALE
FEATURES...AS FVRBL WAA/MOIST ISENTROPIC ASCENT MOVES INTO THE MID
ATLC REGION BTWN THE MAIN (DEEPER) LOW OVER THE MIDWEST REGION AND
THE WEAKER...BAROCLINIC LOW ALONG THE COAST. QPF AMOUNTS ARE ALSO
RELATIVELY CONSISTENT WITH PREVIOUS FCSTS. STILL EXPECTING 1-1.5"
OVER MUCH OF THE REGION...WITH POTENTIALLY HIGHER AMOUNTS (CLOSER
TO 2") OVER THE LWR MD ERN SHORE AND LOWER AMNTS (CLOSER TO 1")
OVER FAR SERN VA/NERN NC.
OTHERWISE...STRONG SOUTHERLY SURGE IN THE LOWER LVLS (50-60 KTS
DOWN TO 950 MB OR ~1500 FT) WILL ALLOW FOR A STEADY RISE IN TEMPS
OVERNIGHT...ESPECIALLY ONCE THE CSTL LOW AND ASSCD WARM FRONT LIFT
NORTH. THE RELATIVE WARMTH ALOFT (MOIST ADIABATIC LAPSE RATES) ALONG
WITH WEAK LLVL STABILITY WILL LIMIT THE CHANCES FOR TSTMS OVERNIGHT...
EVEN THE ELEVATED VARIETY.
WEDNESDAY...
HAVE MAINTAINED CATEGORICAL+ POPS WED MORNING OVER A LARGE PTN OF
THE REGION (HIGHEST NE) AHEAD OF THE COLD FRONT. BY AFTN/EVE...
RAIN CHCS TO DROP SHARPLY FROM SW-NE AS THE DEEP LAYER DRY SLOT
EXPANDS INTO THE FCST AREA. ENSUING SW/WSW FLOW WILL HELP TO DRY
OUT THE LOWER LAYERS FURTHER VIA DOWNSLOPING EFFECTS. BEFORE THE
LLVL FROPA (DEEPER LAYER DRYING)...I.E. DURING THE MORNING
HOURS...AGAIN EXPECT A WINDOW OF OPPORTUNITY FOR TSTMS AS THE
DRYING ENSUES ALOFT WHILE THE LOW LAYERS REMAIN MOIST (I.E.
STEEPENING THETA-E LAPSE RATES). BEST CHCS FOR TSTMS WILL AGAIN BE
ACROSS SERN VA AND NERN NC...WHERE LVLL INSTBY WILL BE MOST FVRBL.
STILL QUITE STRONG SW FLOW NOT FAR OFF THE SFC DURING THIS TIME...
THUS EVEN WITH LIMITED UPDRAFT STRENGTH...STRONG WIND GUSTS WILL
BE POSSIBLE WITH ANY (I.E. SHALLOW) CONVECTION. SEE THE DAY 2
SEVERE WEATHER OUTLOOK FROM SPC FOR FURTHER DETAILS.
TEMPS FOR WED CONTINUE TO BE A CHALLENGE. THE MODELS ARE STILL
RATHER CONSISTENT WITH THE TIMING OF THE FROPA AND ONSET OF LLVL
CAA...THOUGH SPREAD OF GFS/NAM NUMERICAL GUIDANCE REMAINS FAR
APART FOR A DAY 2 FCST. HAVE CONTINUED TO MAINTAIN CONTINUITY WITH
THE PREVIOUS FCST...I.E. HIGHS FROM THE MID 50S OVER NW PTNS
(NORTH-CENTRAL VA) TO AROUND 70/LWR 70S OVER SERN VA/NERN NC.
HIGH PRES RETURNS FOR THU. HIGHS MID 40S-MID 50S.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
COLDER THAN NRML PTRN APRS TO LOCK IN THE END OF THE WK AND FOR
WKND. SFC HI PRES FM THE W SLIDES OVR THE RGN THU NGT THROUGH
FRI...THEN IS SLO TO WKN ON SAT. XTNDD MDLS CONT TO HV DIFFICULTY W/
UPCOMING (NRLY) ZNL PTRN (ALOFT) ACRS CONUS. TMG OF WK SFC LO PRES
TRACKING ACRS THE GULF STATES THROUGH SE CONUS OVR THE WKND...APRS
TO BE (ATTM) TO BE ABT 12 HRS SLOER THAN WAS PORTRAYED YDA. CONTG W/
IDEA OF MSTLY LGT PCPN PTNTLLY BRUSHING (MNLY) SRN HALF VA/NE NC -
OTRW CLDY. LATEST/12Z07 GFS HAS PSBL AREA OF HIER QPF MVG ACRS THE
NRN PORTION OF VA/MD (ASSOCIATED W/ M/ULVL JET DYNAMICS)...THOUGH
UNCERTAIN ABT THIS PSBL PCPN ATTM. ALSO...NOT ALL THAT CONFIDENT ABT
FCST WRMG (IN L/MLVLS) FM SAT NGT INTO SUN MRNG NOR THE "SLOWING DN"
OF THE SYS UPON REACHED THE CST (ERY SUN MRNG) (AS DEPICTED BY
LATEST GFS). FAST/ZNL FLO ALOFT AND SHORT TIME FRAME FOR (SGFNT)
INCRSD LLVL FLO FM THE E OR S AS SFC HI RETREATS/SFC LO PRES TRACKS
BY TO OUR S. W/ THAT IN MIND...AND FOR SIMPLIFICATION AT THIS
STAGE...HV CHOSEN TO GO W/ CHC RA/SN MOST PLCS FM LT SAT INTO ERY
SUN...W/ FURTHER MODIFICATIONS LIKELY AS THE WK PROGRESSES.
&&
.AVIATION /13Z TUESDAY THROUGH SATURDAY/...
GENERALLY VFR CONDITIONS WILL CONTINUE ACRS THE AREA DURING
TODAY...THEN QUICKLY DETERIORATE TO IFR CIGS THIS EVENG/TNGT AS LO
PRES MOVNG UP THRU SC/NC BRINGS RAIN TO THE REGION. IFR CIGS WILL
LIKELY CONTINUE THRU WED MORNG...AS THE LO TRACKS NE ACRS THE ERN
CNTIES. VFR CONDITIONS WILL RETURN WED AFTN ALL SITES AFTR THE
PASSAGE OF A COLD FRNT. HI PRES WILL BLD IN AND OVR THE REGION FOR
WED NGT THRU FRI...PROVIDING VFR CONDITIONS.
&&
.MARINE...
NORTHERLY SURGE THIS MORNING BEHIND WEAK COLD FRONT HAS BROUGHT
SMALL CRAFT ADVISORY CONDS TO THE BAY. ALTHOUGH WINDS WILL DIMINISH
BY MIDDAY...EASTERLY WINDS WILL LIKELY BRING 4 FOOT WAVES INTO THE
MOUTH OF THE BAY BY LATE AFTN. WILL MAINTAIN SCA IN THE BAY THROUGH
WED.
.PREVIOUS DISCUSSION...
WEAK HI PRES CNTRD JUST TO THE N OF THE AREA WILL SLIDE OFFSHR TDY.
LO PRES WILL TRACK NNE UP THE E CST THIS EVENG THRU WED
MORNG...PROVIDING STRNG SCA CONDITIONS OVR THE WTRS. THERE CUD BE A
BRIEF PERIOD (ARND 3 HRS) OF GALE GUSTS OVR THE CSTL WTRS LATER TNGT
INTO WED MORNG...BUT WILL HOLD OFF ON GOING WITH ANY GALE WRNGS AT
THIS TIME. SCA CONDITIONS WILL CONTINUE ALL WTRS WED AFTN INTO ERLY
FRI...DUE TO CAA BEHIND A COLD FRNT AND HI PRES BLDG TWD THE REGION
FM THE WNW.
&&
.HYDROLOGY...
RIVER FLOOD WARNING FOR THE NOTTOWAY AT SEBRELL REMAINS IN EFFECT
THROUGH MIDWEEK. SEE WBCFLSAKQ FOR DETAILS.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...FLOOD WATCH FROM 6 PM EST THIS EVENING THROUGH WEDNESDAY
MORNING FOR MDZ021>025.
NC...FLOOD WATCH FROM 6 PM EST THIS EVENING THROUGH WEDNESDAY
MORNING FOR NCZ012>017-030>032-102.
VA...FLOOD WATCH FROM 6 PM EST THIS EVENING THROUGH WEDNESDAY
MORNING FOR VAZ048-049-060>100.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EST
THURSDAY FOR ANZ633-650-652-654-656-658.
SMALL CRAFT ADVISORY UNTIL 6 AM EST THURSDAY FOR ANZ630>632.
&&
$$
SYNOPSIS...BKH
NEAR TERM...BKH/SMF
SHORT TERM...BKH
LONG TERM...ALB
AVIATION...TMG
MARINE...TMG
HYDROLOGY...
