FXUS61 KLWX 010129 AAA
AFDLWX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
524 PM EST MON NOV 30 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD IN BEHIND A COLD FRONT TONIGHT...AND LAST
INTO TUESDAY. LOW PRESSURE WILL APPROACH THE MID ATLANTIC ON
WEDNESDAY...AND MOVE THROUGH THE REGION WEDNESDAY NIGHT AND
THURSDAY. HIGH PRESSURE RETURNS ON FRIDAY.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
COLD FNT IS THROUGH THE FCST AREA WITH CHILLY TEMPS AND A STIFF NW
BREEZE LEFT IN ITS WAKE. LINGERING SHRA CONFINED TO SERN MD PTN OF
FCST AREA SHD EXIT SHORTLY. THINK WE WILL KEEP AT LEAST SOME CLDS IN
OVERNIGHT IN THE N AND W. WITH WINDS TO PROVIDE MIXING AND CLDS TO
RETARD RADIATIONAL COOLING...THINK CURR FCST MIN TEMPS WILL WORK
FINE. POPS WILL BE LEFT ALONE. CHC IN THE FAR NW FOR UPSLOPE
ACTIVITY. STILL GETTING SOME MIXED REPORTS ALONG THE BORDER
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
OVERNIGHT LOWS WILL DROP BACK INTO SIMILAR CONDITIONS FROM TWO
NIGHTS AGO /NEAR FREEZING/. THE COLDEST TEMPS WON/T SETTLE IN
UNTIL THE PRE-DAWN HRS THO...SINCE THE CLOUDS-PRECIP WILL TAKE A
BIT LONGER TO EXIT THE REGION.
DRYING WILL BEGIN AREAWIDE OVERNIGHT...W/ THE UPPER TROF AXIS
FINALLY MAKING IT/S TREK E OF CNTRL APLCNS AND ACROSS THE REST OF
THE MID ATLC BY THE PRE-DAWN HRS. A WEAK EMBEDDED UPPER SHORTWAVE
WILL THEN SLIDE BY JUST TO THE NORTH...W/ LITTLE MORE THAN BREEZY
CONDITIONS DURING THE AFTN HRS. THE LIGHT PRECIP WILL STAY WELL TO
NORTH OF THE AREA.
AS THIS WAVE PASSES BY...MUCH OF THE CLOUD COVER WILL ALSO REMAIN
NORTH OF THE AREA...W/ THE SRN ZONES CLEARING OUT AND THE NRN HALF
OF THE REGION W/ A FEW PASSING MID-LOW STRATUS. WLY WINDS WILL KEEP
TEMPS MODERATED TUE...ONLY CLIMBING INTO THE L50S FOR MUCH OF THE
AREA.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
HIGH PRESSURE MOVES OFF THE EASTERN SEABOARD TUESDAY NIGHT AS LOW
PRESSURE NEAR THE GULF COAST STRENGTHENS. RETURN FLOW WILL INCREASE
MOISTURE...AND CWA IS LIKELY TO HAVE A DECK OF HIGH/MID CLOUDS TO
START WEDNESDAY MORNING WELL IN ADVANCE OF LOW PRESSURE. CLOUDS WILL
LOWER THROUGHOUT THE DAY WEDNESDAY...AND RAIN WILL LIKELY START
ACROSS THE HIGHLANDS/SHENANDOAH VALLEY AREA DURING THE AFTERNOON
HOURS. RAIN WILL EXPAND NORTH THROUGH THE REST OF THE CWA DURING THE
EVENING. CATEGORICAL POPS ARE IN PLACE.
THERE REMAINS SOME DISAGREEMENT REGARDING THE EXACT TRACK OF THE
CYCLONE. GENERAL TREND IS FOR A MORE WESTERN TRACK. INITIAL SURGE OF
ISENTROPIC LIFT WILL PRODUCE RAIN...BUT CWA MAY ALSO BECOME WARM
SECTORED...WHERE ISOLATED THUNDERSTORMS MAY ALSO BE POSSIBLE
WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE A DRY SLOT WOULD CUT
OFF RAIN ACROSS THE CWA. NAM AND GFS INDICATE QUITE A BIT OF
SHEAR...AND NAM ALSO SHOWS A LITTLE CAPE...SO ITS HARD TO RULE OUT
THUNDER ESPECIALLY EAST OF THE MTNS. 12Z NAM IS ALSO SLOWER THAN THE
12Z GFS AND ITS TIMING WAS PREFERRED.
EXPECT COLDER TEMPERATURES TO MOVE IN THURSDAY NIGHT AND FRIDAY
ACROSS THE CWA. EAST THE MTNS WILL CLEAR OUT SOME...ALTHOUGH CLOUDS
AND SOME SNOW SHOWERS CAN BE EXPECTED ACROSS FAVORED SLOPES OF THE
HIGHLANDS.
12Z GFS HAS TRENDED MORE PESSIMISTIC FOR FRIDAY NIGHT AND
SATURDAY...WITH A STRONGER WAVE BECOMING NEGATIVELY TILTED AS IT
MOVES INTO THE MID ATLANTIC REGION AS SURFACE LOW PRESSURE MOVES UP
THE EASTERN SEABOARD. 12Z CANADIAN INDICATED A SIMILAR TREND. 12Z
ECMWF ALSO SEEMS TO TREND THAT WAY. HOWEVER...MANY OF THE 21Z GEFS
ENSEMBLES MEMBERS ARE NOT AS ROBUST. HAVE DECENT CONFIDENCE IN A
COLDER THAN NORMAL PATTERN IN PLACE...BUT LOW CONFIDENCE IN CHANCES
OF PRECIP. GIVEN THE UNCERTAINTY OF THE LATTER...NO LARGE CHANGES
WILL BE MADE AND HAVE STUCK CLOSE TO HPC. HOWEVER...IF THE
OPERATIONAL 12Z GFS/CANADIAN HOLD...THEN SOME RAIN/SNOW COULD BE
POSSIBLE ACROSS THE MID ATLANTIC IN THE FRIDAY NIGHT/SATURDAY TIME
FRAME. STAY TUNED...
OTHERWISE...HIGH PRESSURE RETURNS OVER THE WEEKEND WITH A COLDER
THAN NORMAL PATTERN CONTINUING. UNSETTLED CONDITIONS COULD COME
BACK EARLY NEXT WEEK.
&&
.AVIATION /22Z MONDAY THROUGH SATURDAY/...
CIGS SHD BE OF THE VFR VARIETY WHERE THEY EXIST OVERNIGHT.
WITH A COLD FRONT NOW PUSHING SE OF I-95...MORE AREAS OF RAIN HAVE
FILLED-IN BEHIND...KEEPING THE AREA MOIST OVER THE NEXT SEVERAL HRS.
THE COMPLETE EXIT OF PRECIP WILL LIKELY BE LATER THIS EVENING INTO
THE LATE NIGHT HRS...W/ A LINGERING ARM OF STEADY RAIN REACHING BACK
INTO WV AT THIS HR. THE LOWEST LEVELS NOT INCREDIBLY MOIST...SO
CIGS/VSBYS STILL ABLE TO REMAIN IN THE LOWEST VFR CATS /ONLY
DROPPING IN THE HIGH-END MVFR FOR A BRIEF PERIOD UNDER HEAVIER RA
ACTIVITY/. BRIEF GUSTY WINDS SHOULD ALSO BE TAKEN INTO ACCOUNT...W/
A WEAK 20-30KT JET A COUPLE THO FT UP.
OVERNIGHT...CONDITIONS WILL IMPROVE AS THIS ACTIVITY MOVES OFF THE
MID ATLC COAST AND HIGH PRESSURE BRIEFLY BUILDS IN ON TUE. A WEAK
UPPER WAVE WILL PASS WELL TO THE NORTH OF THE REGION TUE AFTN...THO
THIS WILL ONLY BRING A PERIOD OF BREEZY SFC WINDS TO THE AREA TUE
AFTN AND NO PRECIP.
HIGH PRESSURE MOVES AWAY TUESDAY NIGHT INTO EARLY
WEDNESDAY...ALLOWING LOW PRESSURE TO APPROACH THE MID ATLANTIC. LOW
PRESSURE WILL PRODUCE RAIN WEDNESDAY NIGHT INTO THURSDAY...WITH IFR
CONDITIONS LIKELY. HIGH PRESSURE RETURNS FRIDAY.
&&
.MARINE...
GUSTS CONT TO RANGE IN 20 KT RANGE ACRS UPR TIDAL POTOMAC AND
UPSTREAM LOCATIONS. WILL EXPAND SCA TNGT TO INCLUDE ALL MARINE
ZONES. UPDTD GRIDS AND CWF ACCORDINGLY. PREVIOUS DISCUSSION
FOLLOWS...
A COLD FRONT WILL CONTINUE DOWN THE LENGTH OF THE BAY/TP THRU THE
REST OF THE AFTN AND INTO EARLY THIS EVENING. STEADY RAIN SHOWERS
WILL CONTINUE THRU THIS PERIOD AS WELL...INTO LATER TONIGHT ALSO.
OVERNIGHT...THE RAIN WILL MOVE OFF THE ATLC COAST...THO GUSTY WINDS
WILL MOVE-IN BEHIND...MAINLY ACROSS THE MIDDLE PORTIONS OF THE BAY.
SCA UP FOR THE WATERS EXCEPT THE 2 WRN ZONES OF THE TP...AS SCA
WINDS OVERALL EXPECTED TO BE MARGINAL...AND THESE LOCALES DO NOT
APPEAR THEY WILL REACH CRITERIA OTHER THAN A BRIEF INTERMITTENT GUST
THRU THE OVERNIGHT HRS AND INTO TUE AFTN.
HIGH PRESSURE MOVES OFF THE EASTERN SEABOARD TUESDAY NIGHT INTO
EARLY WEDNESDAY. LOW PRESSURE LIFT NORTH THROUGH THE MID ATLANTIC
WEDNESDAY NIGHT INTO THURSDAY. GUSTY WINDS AT LEAST TO SMALL CRAFT
ADVISORY LEVELS /AND POSSIBLY GALE FOR A PERIOD/ ARE EXPECTED AS LOW
PRESSURE PASSES BY WEDNESDAY INTO THURSDAY.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST TUESDAY FOR ANZ530>534-
537>543.
SMALL CRAFT ADVISORY UNTIL 4 AM EST TUESDAY FOR ANZ535-536.
&&
$$
UPDATE...RDH
SYNOPSIS...BPP/GMS
NEAR TERM...SBK/GMS
SHORT TERM...GMS
LONG TERM...BPP
AVIATION...BPP/GMS
MARINE...SBK/BPP/GMS
