FXUS61 KLWX 290225
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
925 PM EST SAT NOV 28 2009

.SYNOPSIS...
LOW PRESSURE WILL MOVE UP INTO THE CANADIAN MARITIMES TONIGHT...WHILE
HIGH PRESSURE BUILDS ACROSS THE MID ATLANTIC THIS WEEKEND. A COLD
FRONT WILL PASS THROUGH MONDAY...THEN HIGH PRESSURE BRIEFLY
RETURNS ON TUESDAY. LOW PRESSURE WILL LIKELY IMPACT THE AREA
DURING THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
CLR SKIES AND LTL/NO WND SINCE JUST AFTR SUNSET HAS LED TO FINE
RADL COOLING CONDS ACRS CWFA. CJR ALREADY DOWN TO 30F AT 9PM.
MIN-T AT MOST OUTLYING SITES HV BEEN LWRD SVRL DEG...AND LWRD A
DEG OR TWO IN THE BURBS TOO. FCST MAY STILL END UP TOO WARM...BUT
AM LEERY OF GOING TOO MUCH BLO DEWPTS. NO OTR CHGS OF NOTE THIS
EVNG.
&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
THE TRANSITION PERIOD BETWEEN SYSTEMS FOR THE MID ATLC WILL BE ABOUT 
A DAY...STARTING FROM LATER THIS EVNG AND LASTING THRU SUNDAY EVNG. 
WHAT APPEARS TO BE A QUIET WX-MAP ACROSS THE CONUS IS ACTUALLY A 
PRECURSOR TO ANOTHER COMPLEX SERIES OF WX-SYSTEMS THAT WILL AFFECT 
DIFFERENT PARTS OF THE NATION OVER THE COMING WEEK. THE FIRST OF 
THESE FEATURES WILL BE PART OF A MEANDERING UPPER CUT-OFF LOW OVER 
CNTRL CA CURRENTLY. AS THE LOW SLIDES DOWN INTO THE DESERT SW THRU 
THE NEXT DAY-OR-TWO...AN APPROACHING UPPER WAVE FROM THE NRN ROCKIES 
WILL QUICKLY SLIDE DOWN INTO THE NRN PLAINS/WRN GREAT LAKES OVER THE 
COURSE OF SUNDAY. 

BY LATE AFTN...THIS UPPER TROF /STRETCHING BACK DOWN INTO THE CNTRL 
PLAINS AND HAVING A WEAK CONNECTION TO THE DESERT SW UPPER 
LOW...WILL STREAM WEAKLY FORCED PRECIP FROM THE WEST COAST OF MEXICO 
ALL THE WAY TO SERN CANADA. NO WASH-OUT...JUST AREAS OF LIGHT RAIN 
ALONG A WEAK SFC BOUNDARY. BY LATE SUNDAY...THIS ACTIVITY WILL BE 
PUSHING INTO THE OHIO RVR VLY AND BEGIN TO AFFECT THE WRN ZONES W/ 
STEADY CLOUD COVER BY LATE SUN INTO THE OVERNIGHT HRS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
EXPECT RETURN FLOW TO BE IN PLACE SUNDAY NIGHT WITH SURFACE HIGH 
PRESSURE OVER THE WESTERN ATLANTIC AND A COLD FRONT APPROACHING FROM 
THE WEST. COULD BE A FEW SHOWERS MAKING IT INTO THE HIGHLANDS LATE 
AT NIGHT...BUT A MORE LIKELY TIME FRAME IS MONDAY AS COLD FRONT 
MOVES ACROSS THE AREA. CONVERGENCE ALONG THE FRONT IS NOT FORECAST 
TO BE THAT GREAT...BUT THERE WILL BE SOME MID LEVEL SUPPORT IN TERMS 
OF PVA...SO THINK THAT A BAND OF SHOWERS WILL BE ABLE TO PROGRESS 
ACROSS THE CWA. 09Z SREFS FAVORS MORE CHANCE POPS AS OPPOSED TO 
HIGHER POPS. THIS IS LOWER THAN THE 12Z NAM MOS AND GFS MOS...AND 
CONTINUE TO PREFER LIKELY POPS ACROSS THE CWA. QPF IS EXPECTED TO BE 
LIGHT...ONE TO TWO TENTHS OF AN INCH. MODELS HAVE ALSO ACCELERATED 
THE FRONT AND THIS TREND IS PREFERRED. ADDED SOME TIMING DETAIL TO 
THE GRIDDED DATABASE.

CONTINUING THE SLIGHTLY FASTER TIMING...POPS DECREASE APPRECIABLY 
EARLY MONDAY EVENING EXCEPT ACROSS THE HIGHLANDS WHERE CHANCE POPS 
ARE MAINTAINED DUE TO DEVELOPING UPSLOPE SNOW SHOWERS.

UPSLOPE SNOW SHOWERS CUT OFF TUESDAY AS FLOW BECOMES LESS FAVORABLE 
WITH HIGH PRESSURE BUILDING INTO THE MID ATLANTIC. MEANWHILE...THE 
TAIL OF THE FRONT THAT PUSHES THROUGH THE CWA MONDAY WINDS UP ACROSS 
CENTRAL FLORIDA AND THE GULF OF MEXICO TUESDAY/TUESDAY NIGHT...AND 
GULF LOW PRESSURE DEVELOPS ALONG IT. WITH MID ATLANTIC HIGH PRESSURE 
MOVING OFF THE COAST BY 12Z WEDNESDAY...THIS WILL ALLOW A MOIST 
RETURN FLOW TO RE-DEVELOP WHICH WILL SEND MOISTURE FROM THE GULF LOW 
PRESSURE NORTHWARD ON WEDNESDAY. MODELS ARE A LITTLE SLOWER WITH 
RAIN ONSET...BUT CLOUDS WILL THICKEN UP AND RAIN MAY BREAK OUT LATER 
IN THE DAY ACROSS THE SOUTHERN HALF OF THE CWA WITH ISENTROPIC LIFT 
ON THE INCREASE. 

DISAGREEMENT WITH LOW PRESSURE TRACK CONTINUES. BUT WHETHER IT MOVES 
UP NEAR THE COAST OR UP THE APPALACHIANS THE RESULT IS THE 
SAME...RAIN WEDNESDAY NIGHT. TIMING DISAGREEMENT WILL ALSO NEED TO 
BE RESOLVED...AS IF THE LOW IS SLOWER TO EXIT THEN RAIN MAY LINGER 
INTO AT LEAST THURSDAY MORNING. HAVE CHANCE POPS NOW CONSIDERING THE 
EXIT UNCERTAINTY. 

IN THE WAKE OF LOW PRESSURE...UPSLOPE FLOW WILL BRING SNOW SHOWERS 
BACK TO THE HIGHLANDS THURSDAY NIGHT/FRIDAY. EAST OF THE MTNS SHOULD 
BE DRY THE BALANCE OF THE TIME...BUT AN UPPER TROUGH MAY KEEP SOME 
CLOUDS AROUND AND BELOW CLIMO TEMPERATURES ARE EXPECTED TO SETTLE 
IN.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
WNDS HV DIMINISHED AS HIPRES MVS OHD. SHUD BE CLR/CALM NGT...CONTG
INTO TMRW MRNG. IN RTN FLOW LT SUN MRNG...WNDS WL BECOME SSWLY AOB
10 KT. FEW HI CLDS WL ADVC BY ELY AFTN...AND WL THICKEN/LWR LT
TMRW AFTN-EVE.

COLD FRONT WILL MOVE ACROSS THE REGION ON MONDAY...PRODUCING
SHOWERS THAT MAY CAUSE MVFR CONDITIONS. WIND SHIFT FROM SOUTHWEST
TO NORTHWEST IS EXPECTED AROUND THE AFTERNOON PUSH ON MONDAY. HIGH
PRESSURE BUILDS IN TUESDAY. LOW PRESSURE FROM THE GULF WILL MOVE
NORTH TOWARD THE REGION WEDNESDAY/WEDNESDAY NIGHT.

&&

.MARINE...
WNDS WL BE AOB 10 KT OVNGT UNDER HIPRES. HIPRES EXITS TMRW...
PERMITTING A SSWLY FLOW TO SET UP. SPDS WL STILL BE BLO 10 KT FOR
THE MRNG...INCR TO 10-12 KT DURING THE AFTN.

COLD FRONT MOVES ACROSS THE WATERS MONDAY AFTERNOON/EARLY 
EVENING...WITH A GUSTY NORTHWEST WIND DEVELOPING BEHIND THE FRONT 
MONDAY NIGHT/TUESDAY WHICH COULD EVENTUALLY WARRANT A SMALL CRAFT 
ADVISORY. HIGH PRESSURE TUESDAY NIGHT MOVES OFF THE COAST WEDNESDAY. 
GULF LOW PRESSURE MAY MOVE UP THE MID ATLANTIC WEDNESDAY 
NIGHT/THURSDAY...WHICH COULD ALSO INSTIGATE SMALL CRAFT ADVISORY 
CONDITIONS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...GMS/PELOQUIN
NEAR TERM...HTS
SHORT TERM...GMS
LONG TERM...PELOQUIN
AVIATION...HTS/PELOQUIN
MARINE...HTS/PELOQUIN