FXUS63 KGRB 252108
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
308 PM CST WED NOV 25 2009

.SHORT TERM...TONIGHT AND THANKSGIVING DAY. 

FORECAST CONCERNS THIS PERIOD POPS AND PCPN TYPE.

AT 20Z CLOSED UPPER OVER CENTRAL IOWA...WHILE OPEN WAVE LIFTING
OUT THROUGH LOWER MI. AT THE THE SURFACE 1002MB LOW OVER NORTHERN
LAKE MI WITH INCREASING NORTHWEST WIND OVER STATE. MUCH OF DAY...CWA
BETWEEN THE TWO SYSTEMS WITH PERIODIC LIGHT RAIN OR DRIZZLE. AREA
RADARS NOW SHOWING INCREASING AREA OF PCPN OVER SOUTHERN
WI...NORTHERN IL.

MODELS FAIRLY CONSISTENT THIS PERIOD. PCPN AREA TO SOUTH EXPECTED
TO ROTATE NORTH INTO CWA THIS EVENING. QUESTION IS HOW FAR NORTH.
HAVE BOOSTED POPS SOUTH...THOUGH STAYED WITH CHANCE CATEGORY NORTH
AS QG/FRONTOGENTIC FORCING FOCUSED OVER WI/IL BORDER LEAVING CWA
ON NORTHERN FRINGES. HAVE BACKED OFF FURTHER ON SNOW...WITH MODEL
CROSS SECTIONS SHOWING BOUNDARY LAYER REMAINING TOO WARM AS
COLDEST AIR WITH LOW TO SOUTH OF CWA. DO HAVE SOME CONCERN WITH
STEP LAPSE RATES THIS EVENING. WILL INDICATE SNOW MIXING IN
CENTRAL AROUND MIDNIGHT...THOUGH BY THAT TIME BULK OF PCPN TO
EAST. WILL END PCPN WEST TO EAST TONIGHT/THU MORNING WITH RIDGE
BUILDING IN. 

NORTHWEST FLOW OVER AREA LEADS TO CONCERN FOR LAKE EFFECT OVER
PARTS OF NORTH CENTRAL WI LATE TONIGHT AND THU. THROUGH
12Z...SHEAR IN LOW LEVEL WINDS AND MARGINAL DELTA T'S /11-13/ TO
LIMIT SNOWFALL. ON THU...WINDS AND TEMPS BETTER FOR LAKE EFFECT
THOUGH SUBSIDENCE AND DRYING WORK AGAINST ANY SIG ACCUMULATIONS.
WILL STAY WITH PREVIOUS FORECAST AMOUNTS.

.LONG TERM...THU NGT THRU NXT WED. A RATHER PROGRESSIVE LOOKING
FLOW ACROSS THE CONUS NXT WEEK ALTHO THERE ARE MORE SIGNS POINTING
TO RIDGING TAKING PLACE OVR THE WEST COAST AND WRN ATLANTIC. THIS
PLACES THE MIDDLE OF THE COUNTRY UNDER A SERIES OF LONGWV TROFS
THAT DROP SE OUT OF WRN CANADA. ONE TROF IS TO ARRIVE OVR THE
GREAT LKS EARLY NXT WEEK WITH THE NXT ONE POSSIBLY HOLDING OFF TIL
JUST BEYOND THE FCST PERIOD. EXPECT TEMPS FOR THE MOST PART TO BE
AT OR SLIGHTLY ABV NORMAL NXT WEEK.

SYSTEM CONTS TO GET DRIVEN EAST AS A BROAD UPR RDG PUSHES INTO THE
PLAINS THU NGT. AT THE SFC...A WEAK RDG OF HI PRES IS FCST TO MOV
INTO WRN WI BY 12Z FRI...THEREBY BRINGING DRIER AIR TOWARD NE WI.
WNDS WL BE LGT...BUT STILL HAVE A NW COMPONENT TO THEM.
COMTEMPLATED ADDING SOME LINGERING FLURRIES TO VILAS CNTY...BUT
WITH THE FLOW BECOMING MORE ANTICYCLONIC...ANY FLURRY ACTION WOULD
BE INCONSEQUENTIAL TO THE FCST SO KEPT EVERYONE DRY THU NGT. A
COOL NGT ANTICIPATED (COMPARED TO PREV NGTS) WITH READINGS DIPPING
INTO THE 20S. IN FACT...WOULD NOT BE AT ALL SURPRISED TO SEE THE
COLD SPOTS OF THE NORTH DROP INTO THE TEENS. 

NE WI GETS ON THE BACKSIDE OF THE SFC RDG ON FRI WHICH ALLOWS WNDS
TO BACK S-SW DURING THE AFTERNOON. ONSET OF WAA DVLPS DURING THE
COURSE OF THE DAY AND EXPECT TO SEE A GRADUAL INCREASE IN HI/MID
CLDS. UNDER PARTLY SUNNY SKIES...TEMPS WL STILL BE ABLE TO REACH
THE UPR 30S TO LWR 40S. 

QUIET WEATHER CONDITIONS PERSIST THRU FRI NGT AS THE FLATTENED UPR
RDG REACHES THE WRN GREAT LKS. EVER SO SLIGHTLY WARMER AIR ALOFT
WL PREVENT TEMPS FROM GETTING AS COOL AS THU NGT WITH MOST
LOCATIONS FALLING INTO THE LWR 20S NEAR THE MI BORDER...TO AROUND
30 DEGS NEAR LK MI. WEAK UPR RDG TO MOV ACROSS THE WRN GREAT LKS
ON SAT SO HAVE KEPT THE FCST AREA DRY PER PREV FCST. A WEAK CDFNT
IS FCST TO APPROACH WRN WI SAT AFTERNOON...BUT NOT HAVE ANY IMPACT
ON OUR WEATHER. A SOMEWHAT MILD DAY EXPECTED WITH 8H TEMPS AROUND
+4C. LOOK FOR MAX TEMPS TO REACH AROUND 40 NORTH...TO THE MID 40S
SOUTH. 

THE CDFNT PASSES THRU THE REMAINDER OF WI SAT NGT...BUT ANY
MEASURABLE PCPN MAY BE HARD TO COME BY AS ALL THE UPR SUPPORT IS
FOCUSED BACK OVR THE UPR MIDWEST CLOSER TO THE LONGWV TROF. HAVE
ADDED A SLGT CHC OF LGT SNOW TO N-CNTRL WI LATE SAT NGT AS THE
FORCING INCREASES. BY SUNDAY...SOME OF THE MDLS ATTEMPT TO SPLIT
THE LONGWV TROF INTO TWO SEPARATE BRANCHES. THE NRN BRANCH SHIFTS
E-NE INTO ONTARIO THEREBY TAKING BETTER FORCING/LIFT NORTH OF THE
FCST AREA. FOR NOW...PREFER TO ONLY MENTION A SLGT CHC OF LGT SNOW
ACROSS THE NORTH AND DOWNPLAY ANY PCPN TO EITHER FLURRIES OR
SPRINKLES OVR CNTRL/E-CNTRL WI. TEMPS BY SUNDAY WL BEGIN TO COOL
DOWN WITH MOST LOCALES ONLY REACHING THE MID OR UPR 30S.

LINGERING LGT SNOW SHWRS OR FLURRIES TO CONT THRU SUNDAY NGT AS
THE UPR TROF (AND EMBEDDED SHRTWVS) MOV ACROSS THE RGN. TIMING OF
THIS UPR TROF WL BE A KEY TO MON'S FCST AS THE FASTER GFS CLRS OUT
ANY PCPN...WHILE THE SLOWER ECMWF ALLOWS THE SRN BRANCH OF THE
LONGWV TROF TO DVLP A NEWD MOVG STORM. GFS SOLN WOULD SAY NO PCPN
FOR NE WI...HOWEVER THE ECMWF SOLN BRINGS THE NRN EDGE OF A PCPN
SHIELD INTO THE SE THIRD OF WI. TYPICALLY...THE ECMWF HAS A BETTER
HANDLE ON THESE SPLIT FLOW REGIMES...SO HAVE ADDED A SML POP TO
SUNDAY NGT/MON'S FCST FOR E-CNTRL WI. 

HI PRES TO THEN BRING A RETURN TO QUIET WEATHER CONDITIONS FOR MON
NGT THRU TUE NGT BEFORE ATTN TURNS TOWARD THE NXT UPR TROF WHICH
DIVES SE INTO THE CNTRL CONUS NXT WED. A WEAK CDFNT IS PROGGED TO
MOV THRU WI LATE TUE NGT/EARLY WED MORNING...BUT ESSENTIALLY PASS
THRU DRY AS MSTR IS LACKING INITALLY. HAVE ALSO KEPT THE REST OF
WED DRY AS WELL AS THE BULK OF THE FORCING IS FCST TO STILL BE
WELL TO OUR WEST.
&&

.AVIATION...COLD UPPER LOW DROPPING SOUTH TO WEST OF THE
AREA OVERNIGHT. PCPN WITH SYSTEM TO ROTATE NORTH INTO AREA THIS
EVENING. COLDEST AIR TO THE SOUTH...THOUGH CHANCE AFTER MIDNIGHT
TO SEE SOME SNOW MIX IN. MVFR/IFR CIGS AND VSBY TO IMPROVE LATE
TONIGHT AND THU MORNING WITH INCREASING NORTHWEST WIND AS SURFACE
LOW SYSTEM PULLS OUT.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$
TE/KALLAS