FXUS61 KLWX 020110
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
805 PM EST TUE DEC 1 2009
.SYNOPSIS...
HIGH PRESSURE OVER THE AREA WILL PUSH OFF THE COAST TONIGHT. LOW
PRESSURE IN THE NORTHERN GULF OF MEXICO WILL APPROACH THE MID
ATLANTIC STATES WEDNESDAY...BEFORE MOVING THROUGH THE REGION
WEDNESDAY NIGHT. HIGH PRESSURE BUILDS IN FRIDAY. A COASTAL
DISTURBANCE DEVELOPS OFF THE CAROLINAS EARLY SATURDAY. HIGH
PRESSURE WILL RETURN FOR THE WEEKEND.
&&
.NEAR TERM /TONIGHT/...
FOR THE UPDATE...EVERYTHING IS PROGRESSING AS PLANNED. SOME HIGH
THIN CLDS SHOWING UP SRN ZONES ON IR SAT LOOP. EXPECT THIS TO SLOWLY
ADVECT NORTHWARD...LWR AND THICKEN INTO TMRW. LARGE BLOB OF PRECIP
OVR DEEP SOUTH SEEMS A SAFE BET FOR THE AREA TMRW...ARRIVING IN
METRO AREAS IN THE AFTERNOON. TEMPS LOOK FINE FOR TNGT. LAST HIGH
TIDE SHOWED A VERY SLIGHT ANOMOLY OVER ASTRONOMICAL PREDICTION AT A
FEW SITES...ON THE ORDER OF 0.4 OF A FOOT. THIS SHD INCR AS S TO SE
FLOW PICKS UP TMRW. SHORT DURATION OF UPRIVER AND UP BAY FLOW SHD
PRECLUDE NEED FOR WARNINGS...BUT LATER SHIFTS MAY NEED TO TOSS OUT
AN ADVISORY.
PREV...
A PLSNT...COOL NGT ON TAP FOR THE RGN. HIGH PRES IN CONTROL TNGT.
LOWS RANGE FM A30 IN THE MTNS TO A40 ALONG THE BAY AND IN THE MAJOR
CITIES.
&&
.SHORT TERM /WEDNESDAY/...
CLDS BEGIN OVRSPREADING THE SW PORTION OF THE CWA DURG MRNG HRS
AHD OF THE GULFMEX LOW. POPS STARTING AS CHC IN THE SW DURG
MRNG...SPREADING NE DURG MIDDAY AND FINISHING THE DAY AS
CATEGORICAL.
AM NOT SURE EXACTLY HOW STRONG THE WINDS ARE GOING TO GET WED
AFTN...BUT PLACE WHERE THE STRONGEST WINDS ARE PSBL WL BE ALONG
THE E FACING MTN SLOPES IN THE SWRN PART OF THE CWA. GFS SHOWING
SE WINDS 30-35 KT AT 18Z. DON'T FEEL THESE ARE UP TO WIND WATCH
CRITERIA (SUSTAINED 40 KT G 58 KT) BUT WL HV GUSTS INTO THE 30S
AT HIGHER ELEVS. STRONG WAA LOOKS LKLY AT HIGHER ELEVS AS WELL WED
AFTN. TEMPS WL RANGE FM LM50S IN SW VA TO M40S NW CORNER.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE MED-LONG RANGE FEATURES TWO WX-SYSTEMS FOR THE MID ATLC. ONE
IS THE EXITING LOW PRESSURE SYSTEM FOR WED INTO THU...THE OTHER IS
ANOTHER ERN SEABOARD WAVE OF LOW PRESSURE TO EFFECT THE AREA SAT
INTO SUN.
BY LATE WED...THE FIRST SYSTEM WILL BE WELL ON ITS WAY UP THE
SOUTHEAST...PUSHING THE INTENSE WARM SECTOR ACROSS THE ERN
SEABOARD...W/ THE MAIN SFC LOW SLIDING UP THRU THE TENNESSEE AND
OHIO RVR VALLEYS. SOME OF THE MORE HI-RES MODELS AVAILABLE LIKE THE
GEM-REGIONAL/NAM AND LOCAL WRF RUNS SHOW SEVERAL LARGE AREAS OF AT
LEAST MODERATE QPF STREAMING INTO THE IMMEDIATE CWA FROM LATE
EVENING WED INTO THE PRE-DAWN HRS THU. STORM TOTAL QPFS BETWEEN
1-1.5 INCHES /WITH LOCALLY HIGHER AMOUNTS/ AND MODEL PWATS ROUGHLY
WITHIN THE SAME RANGE. FORWARD SPEED OF THIS SYSTEM WILL ALREADY
VERY QUICK...SO INLAND FLOODING NOT MUCH OF CONCERN EVEN W/ THE
AMOUNT OF QPF AS SWLY WINDS PUSH THIS ACTIVITY QUICKLY UP THE ERN
SEABOARD. MUCH OF THE STRONGER CONVECTIVE ELEMENTS AND EMBEDDED
HEAVIER RAINFALL WILL BE DOWN ACROSS THE COASTAL CAROLINAS AND VA
TIDEWATER REGION. THERE IS INDICATION THAT ENOUGH INSTABILITY WILL
BE AVAILABLE IN THE LOWEST LEVELS FOR EMBEDDED CONVECTION OR AT
LEAST CONVECTIVE-TYPE PRECIP ACROSS THE ERN PART OF THE CWA.
AS THE NEGATIVELY ROTATING UPPER TROF-CLOSED UPPER LOW DRIVES NEWD
OVER THE CNTRL APLCNS...THE BULK OF THE ACTIVITY WILL BE
ACCELERATING UP INTO NEW ENGLAND BY SUNRISE THU. RESIDUAL SHOWERS
AND STILL GUSTY SFC WINDS WILL BE PRESENT OVER THE REGION. BY THU
AFTN...CONDITIONS WILL BE IMPROVING THO WINDS WILL STILL BE BREEZY
AND WLY BY LATE AFTN W/ A FEW BACKSIDE-UPSLOPE SHOWERS ACROSS
WINDWARD SIDE OF THE ALLEGHENY MTNS.
SWLY UPPER FLOW WILL BE IN PLACE OVER THE REGION FRI INTO SAT.
OVERNIGHT LOWS WILL BE COLDER THAN IN THE SHORT-TERM SINCE
CONDITIONS WILL BE DRIER IN THE WAKE OF THE NEXT WX-SYSTEM. THIS
SYSTEM...STILL VERY MUCH IN QUESTION SINCE IT WILL BE A COMBINATION
OF SYNOPTIC ELEMENTS COMING TOGETHER OVER THE LOWER MISSISSIPPI VLY
LATE THIS WEEK. SEVERAL UPPER VORTS TAKING A WIDE-SWING DOWN ACROSS
THE NRN PLAINS ARE EXPECTED TO DIVE DOWN INTO THE SOUTHEAST INTO THE
COMING WEEKEND...DEVELOPING ANOTHER GULF-COAST LOW PRESSURE SYSTEM
TO RIDE UP THE ERN SEABOARD. NEWEST GUIDANCE RETREATING A BIT FROM
EARLIER RUNS THAT HAD MORE OF A WINTRY SYSTEM FOR MID ATLC ON
SAT/SUN. TRENDS NOW SHOW A WEAKLY FORCED AND REGIONAL-SCALE AREA OF
LIGHT PRECIP SPREADING OVER THE MID ATLC AS THE SFC LOW SPINS WELL
OFF THE ATLC COAST SAT INTO SUN. FOR NOW A LOW CHANCE EVENT W/ A MIX
OF RAIN/SNOW FOR LATE SAT /MAINLY RAIN DURING THE DAYTIME HRS AS
TEMPS ARE EXPECTED TO TOP-OUT IN THE U30S-L40S. HIGH PRESSURE WILL
THEN BUILD INTO THE MID ATLC FOR THE FIRST PART OF NEXT WEEK.
&&
.AVIATION /TONIGHT THROUGH SUNDAY/...
VFR CONDS TNGT AND WED MRNG. SKIES WL LKLY DROP INTO MVFR CAT BY
LATE WED AFTN.
STRONG WINDS AT THE SFC AND ALOFT WILL BE IN PLACE WED AFTN
/STRONGEST OVERNIGHT/ AND INTO THU AFTN. THE LOW PRESSURE SYSTEM
WILL MOVE WELL NE OF THE MID ATLC ON THU MRNG. ANOTHER COUPLE OF
DAYS OF IMPROVEMENT INTO EARLY SAT. A LIGHT MIX OF RAIN/SNOW MAY BE
POSSIBLE ON SAT W/ ANOTHER LOW PRESSURE SYSTEM PASSING TO THE EAST
OF THE AREA FROM OFF THE COAST.
&&
.MARINE...
NO HAZARDS ON THE WATERS TNGT. SCA IN EFFECT FOR WED AFTN AHEAD
OF THE LOW PRES SYSTEM COMING FM GULF OF MEX.
A ROUGH NIGHT ON THE WATERS OF THE CHESAPEAKE AND TIDAL POTOMAC W/
GUSTY WINDS IN PLACE...BEGINNING WED EVENING AND LINGERING INTO THE
MID MORNING HOURS ON THU. WINDS WILL DECREASE BY LATER IN THE DAY
THU AND STAY FAIRLY LIGHT INTO THE WEEKEND...THO ANOTHER LOW
PRESSURE SYSTEM WILL PASS OFF THE ATLC COAST ON SAT...POSSIBLY
BRINGING BACK SCA CONDITIONS THIS WEEKEND.
&&
.TIDES/COASTAL FLOODING...
WATER LVLS ARE CURRENTLY BLO NRML LVLS. THESE SHOULD RECOVER TNGT
AND RISE ABV NRML WED AFTN ON STRONG SE FLOW. HOWEVER IF CSTL FLDG
SHOULD OCCUR IT WOULD BE SHORT LIVED AS WIDS GO BACK TO THE W ON
THU.
GOING INTO THE AFTN HRS OF WED...TIDES WILL ROUGHLY AT NORMAL LEVELS
BUT A GRADUALLY INCREASING SELY FLOW WILL BEGIN TO CREATE A GREATER
SEPARATION INTO THE EVNG HRS. EVEN INTO THE OVERNIGHT HRS...A
PERSISTENT AND STRONG SE-SLY FLOW WILL BE PUSHING UP THE BAY. FOR
THE WED LATE NIGHT/OVERNIGHT AND THU EARLY MORNING TIDE CYCLES...AT
LEAST MINOR COASTAL FLOODING ALONG LOW LAYING AREAS ACROSS THE WRN
SHORES OF THE MD CHESAPEAKE BAY AND THE TIDAL POTOMAC RIVER. BY THE
MID MORNING HRS ON THU...WINDS WILL SHIFT TO MORE WLY AND STILL
BREEZY...WHICH WILL UNDERCUT THE POSITIVE ANOMALIES BUT STILL KEEP
AT LEAST A LOW THREAT OF FLOODING OVER THE NEXT COUPLE OF TIMES OF
HIGH TIDE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM WEDNESDAY TO 6 AM EST
THURSDAY FOR ANZ530>543.
&&
$$
PRODUCTS...WOODY!/GMS
UPDATE...RDH
