FXUS63 KGRB 242202
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
402 PM CST THU DEC 24 2009

.SHORT TERM...TONIGHT THROUGH CHRISTMAS DAY. CHALLENGE FOR THIS
PART OF THE FORECAST IS PRECIPITATION TYPE. TEMPERATURES IN THE
BOUNDARY LAYER ARE IMPORTANT TONIGHT IN THE EAST CENTRAL PART OF
THE STATE AS THAT WILL DETERMINE WHETHER WE GET SEVERAL HOURS OF
FREEZING RAIN AND SLEET OR JUST RAIN. WE ALSO HAVE TO WORRY ABOUT
THE ELEVATED ABOVE FREEZING LAYER THAT IS FORECAST TO WRAP
WESTWARD ACROSS THE REGION TONIGHT. THE NAM IS THE WARMEST AND
WOULD ARGUE FOR A CHANGEOVER TO FREEZING RAIN OR SLEET EVEN IN THE
NORTHCENTRAL PART OF THE STATE. IT IS NOT TOO DIFFICULT TO BELIEVE
THAT A WARM LAYER COULD WRAP THAT FAR BACK INTO THE FORECAST AREA
GIVEN THE STRENGTH OF THE APPROACHING SYSTEM AND CONSIDERING HOW
FAR WEST IT IS TRACKING. 

SO EXPECT SNOW MIXED WITH SLEET AND FREEZING RAIN AT TIMES IN THE
NORTHCENTRAL COUNTIES...MOSTLY SLEET AND FREEZING RAIN IN CENTRAL
AND FAR NORTHEAST WISCONSIN AND RAIN WITH A BRIEF PERIOD OF
FREEZING RAIN OR SLEET ELSEWHERE. COLD AIR ARRIVES FROM THE
SOUTHWEST CHRISTMAS DAY AND SHOULD CHANGE OVER THE RAIN TO SNOW.

.LONG TERM...FRI NGT THRU NXT THU. WL STILL BE DEALING WITH LRG
COMPLICATED SYSTEM THRU THE UPCOMING WEEKEND WITH ADDL SNOW
ACCUMULATIONS. FOR NXT WEEK...A SPLIT FLOW COMING OFF THE PACIFIC
WL PERSIST THRU THE MIDDLE OF THE WEEK WITH AN AMPLIFYING MID-LVL
TROF WORKING EWD INTO THE WRN CONUS MON...SRN PLAINS BY NXT WED.
STILL IFFY ON WHAT RAMIFICATIONS THIS TROF WL BRING TO NE WI AS
THE MAIN SFC SYSTEM TO DVLP ALONG THE GULF COAST WHILE WEAKENING
TROF HEADS NE TOWARD THE GREAT LKS. IN OTHER WORDS...NO MAJOR
STORMS ON THE HORIZON. 

MDLS AGREE THAT THE SFC LOW WL COME OUT OF ITS LOOP DE LOOP OVR
CNTRL IA FRI NGT AS THE CLOSED UPR LOW LIFTS NORTH TOWARD SE WI. A
SHEARED SHRTWV IS EXPECTED TO ROTATE THRU THE FCST AREA FRI
EVENING AND COMBINED WITH FAVORABLE FRONTOGENETICAL FORCING...WE
MAY SEE A QUICK INCH OR TWO OF SNOW FALL BEFORE THE SNOW TAPERS
OFF A BIT OVRNGT AS THE DRY SLOT ROTATES IN FROM THE SE. HAVE GONE
WITH CATEGORICAL POPS FOR THE ENTIRE FCST AREA WITH TEMPS NEAR
BIAS-CORRECTED VALUES (UPR TEENS NORTH TO MID 20S NEAR LK MI).

MORE POTENT LOOKING SHRTWV IS EXPECTED TO ROTATE NW INTO CNTRL
SECTIONS OF WI ON SAT. THIS PROJECTED TRACK...PLUS SOME LK
ENHANCEMENT DUE TO AN E-SE WND...WOULD FAVOR SLIGHTLY HIGHER
QPF/SNOW AMTS OVR ERN WI. WOULD NOT BE SURPRISED TO SEE YET
ANOTHER INCH OR TWO OF ACCUMULATION FOR THE EAST WITH LESSER AMTS
(LESS THAN AN INCH) FARTHER WEST. DO NOT ANTICIPATE MUCH OF A TEMP
RISE ON SAT WITH THICK CLD CVR/UPR LOW OVRHD.

AS THE UPR LOW HEADS BACK SOUTH INTO ERN IA SAT NGT...THE SFC LOW
WL THEN PIVOT NWD INTO CNTRL SECTIONS OF LK MI BY 12Z SUNDAY.
ONSHORE WNDS...VARIOUS WEAK SHRTWVS ROTATING AROUND AND A GENERAL
WEAK FORCING TO ALL WORK TOGETHER TO CONT BRINGING LGT SNOW TO THE
RGN. ONCE AGAIN...A TOUCH MORE SNOW POTENTIAL FOR THE EAST WITH
MOST AREAS RECEIVING ANOTHER INCH OF ACCUMULATION. SLOWLY FILLING
UPR LOW FINALLY MAKES A "SIGNIFICANT" EWD MOV ON SUNDAY WITH THE
LOW REACHING NE INDIANA BY 00Z MON. CHC OF LGT SNOW AND FLURRIES
WL PERSIST THRU THE DAY AS VARIOUS SHRTWV CONT TO ROTATE SWD THRU
WI AND CYCLONIC FLOW STILL IN THE VCNTY. WHILE QPF AMTS ARE
EXPECTED TO BE MINIMAL (< 0.10")...THIS COULD STILL DROP AN INCH
OF SNOW SOMEWHERE IN THE FCST AREA.

NW FLOW ALOFT SUNDAY NGT WL VEER MORE NORTH ON MON AS A CDFNT
DROPS SOUTH THRU WI. 8H TEMPS OVR WRN LK SUPERIOR FALL TO AROUND
-16C WHICH IS SUFFICIENT FOR LK EFFECT SNOW SHWRS TO DVLP AND PUSH
INTO NRN WI. PBLM FOR ANY SIGNIFICANT SNOW IS THAT FCST SNDNGS
SHOW A LOW-LVL INVERSION AROUND 4K FT AND AN INFLUX OF DRIER AIR
FROM HI PRES BUILDING SE FROM CANADA. HAE KEPT A CHC POP FOR VILAS
CNTY WITH SLGT CHCS A TIER OF COUNTIES SOUTH AND EAST. THIS HI
PRES SETTLES OVR THE GREAT LKS BY TUE PROVIDING FOR SOME SUNSHINE
WITH THE BRUNT OF THE COLDER AIR SHFITING OFF TO THE EAST. RETURN
FLOW DVLPS TUE NGT AS THE SFC HI MOVS TOWARD THE ERN GREAT LKS.
EXPECT TO SEE AN INCREASE IN CLDS WITH TIME ESP BY WED AS THE
SHRTWV TROF LIFTS NE INTO THE CNTRL CONUS. APRS AT THIS TIME THAT
ANY PCPN ASSOCIATED WITH THIS UPR TROF WL REMAIN JUST TO OUR
SOUTH...THUS HAVE REMOVED THE PCPN CHCS FROM WED.

THE SHRTWV TROF REACHES THE WRN GREAT LKS WED NGT AND IS PROGGED
TO INTERACT WITH AN EWD MOVG CDFNT TO BRING A CHC OF LGT SNOW TO
NE WI. SOME OF THIS LGT SNOW MAY CARRY OVR INTO THU WITH THE UPR
TROF STILL IN OUR VCNTY. NOT MUCH IN THE WAY OF COLD AIR BEHIND
THE FNT...THEREFORE TEMPS SHOULD REMAIN JUST A BIT BLO NORMAL FOR
THE LAST DAY OF 2009.
&&

.AVIATION...CIGS AND VSYBYS WILL BECOME IFR JUST ABOUT EVERYWHERE
BY LATE EVENING AND REMAIN SO OVERNIGHT. IN ADDITION...FREEZING
RAIN AND SLEET IS EXPECTED AWAY FROM THE LAKE AND BAY WHICH MAY
REQUIRE IN FLIGHT AND GROUND DEICING. CIGS AND VSBYS WILL
GRADUALLY INCREASE CHRISTMAS DAY BUT REMAIN IN IFR OR LWO MVFR RANGE.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 AM CST FRIDAY FOR WIZ038-039-048-
049-073-074.

WINTER STORM WARNING UNTIL 6 PM CST FRIDAY FOR WIZ005-010>013-
018>021-030-031-035>037-045.

&&

$$
RDM/KALLAS