FXUS63 KGRB 090044 AAA
AFDGRB

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GREEN BAY WI
644 PM CST TUE DEC 8 2009

.UPDATE...CURRENT PCPN TRENDS SEEM TO BE WELL-HANDLED BY THE 18Z
GFS ATTM...WITH A BROAD AREA OF MDT/HVY PCPN NEARING THE S WI BORDER.
THIS PCPN IS THE RESULT OF STG ISENT LIFT...UPPER DIVG AND LEAD S/W
ENERGY. THE GFS ALSO HAS A GOOD HANDLE ON THE POSN OF THE DRY SLOT...
WHICH IS PUNCHING FROM MO INTO FAR SE IA. A 993 MB SFC LOW IS
CURRENTLY SITUATED IN SW MO...A BIT SW OF THE GFS POSN AT 00Z.
PRESSURE FALLS STILL SUPPORT A NORTHEAST MOVMT TOWARD FAR SE WI
LATE TONIGHT. RADAR TRNDS SUPPORT AN INCREASE IN SNOW INTENSITY
ACROSS C/EC WI DURING THE NEXT FEW HOURS.

HAVE A COUPLE CONCERNS...WHICH WILL BE MONITORED THIS EVG. FIRST
OF ALL...NEED TO WATCH THE MOVT OF THE DRY SLOT...WHICH THE GFS
SUGGESTS MAY CLIP FAR EC WI. ALSO...AM A BIT CONCERNED ABOUT TEMPS
IN EC WI...AS MTW IS ALREADY AT 34...AND MET GUIDANCE SHOWS SFC
AND LLVL WET BULB TEMPS WARMING THERE OVERNIGHT. IF ENOUGH WARMING
OCCURS...WE COULD SEE A MIX...ESP NEAR THE LKSHR. OTHER PSBL CONCERN
IS WHETHER OR NOT WE'LL SEE GUSTS TO 35 MPH IN C/FAR NE TO VERIFY
A BLIZZARD WARNING. NOT WORRIED ABOUT THE FOX VALLEY/LKSHR
AREAS...WHERE FUNNELING DOWN THE BAY SHOULD EASILY RESULT IN
GUSTS EXCEEDING 35 MPH...HOWEVER CONFIDENCE IS NOT AS HIGH FOR
AREAS FARTHER INLAND.

KIECKBUSCH
&&

.PREV DISCUSSION...ISSUED AT 336 PM CST TUE DEC 8 2009...

SHORT TERM...TONIGHT AND WEDNESDAY.

A NEGATIVELY TILTED UPPER LEVEL TROUGH AND A STRONG SURFACE LOW
PRESSURE SYSTEM WILL BRING EXTREME WINTER WEATHER CONDITIONS TO
THE FORECAST AREA TONIGHT AND WEDNESDAY. A WINTER STORM WARNING
FOR THE ENTIRE FORECAST AREA HAS BEEN UPGRADED TO A BLIZZARD
WARNING FOR ALL BUT NORTH-CENTRAL WISCONSIN THROUGH MIDNIGHT
WEDNESDAY NIGHT.

MODELS SHOWED A 500MB TROUGH OVER THE HIGH PLAINS THIS AFTERNOON
TAKING ON A NEGATIVE TILT WITH A CLOSED 500MB LOW DEVELOPING. THE
LOW WAS FORECAST TO REACH NORTHERN ILLINOIS BY 12Z WEDNESDAY AND
CONTINUE TO NEAR EASTERN LAKE SUPERIOR BY 00Z THURSDAY. THE
SURFACE LOW THAT IS EXPECTED TO BE MOVING OUT OF THE SOUTHERN
PLAINS THIS AFTERNOON WILL BECOME MUCH MORE TIGHTLY WOUND AS IT
CONTINUES TO AROUND KENOSHA/ZION BY 12Z...THEN TO LAKE HURON BY
00Z THURSDAY. SURFACE WINDS AROUND THE LOW WERE FORECAST TO
INCREASE INTO THE 20 TO 30 KNOT RANGE AS THE LOW PASSES SOUTHEAST
OF THE FORECAST AREA. AT THE SAME TIME...925MB WINDS WERE FORECAST
IN THE 30 TO 40 KNOT RANGE AND 850MB WINDS WERE EVEN STRONGER. IT
WILL NOT TAKE MUCH MIXING TO GET SUSTAINED OR FREQUENT GUSTS TO 35
MPH FOR SEVERAL HOURS. WINDS THIS STRONG SHOULD EASILY LOWER
VISIBILITIES TO NEAR ZERO WHEN COMBINED WITH FALLEN AND FALLING
SNOW.

MADE MINOR CHANGES TO HPC SNOWFALL GUIDANCE...BUT TOTALS WILL BE
HIGH ACROSS THE AREA. THE NORTHWEST PART OF THE CWA IS EXPECTED TO
EXPERIENCE WEAKER WINDS SO HAVE LEFT THE WINTER STORM WARNING IN
EFFECT THERE RATHER THAN UPGRADE TO BLIZZARD.

ONE SERIOUS CONCERN IS WHETHER ENOUGH WARM ADVECTION WILL OCCUR IN
EASTERN WISCONSIN TO RESULT IN RAIN OR MIXED PRECIPITATION. THIS
WILL NEED TO BE MONITORED BY SUBSEQUENT SHIFTS TO MAKE SURE IT
DOES NOT BECOME A PROBLEM.

COLLABORATION LED TO A LARGER AND LONGER BLIZZARD WARNING THAN WE
WOULD LIKE...BUT HOLES IN FORECAST GRAPHICS LOOK EXTREMELY
BAD...SO HAVE GONE ALONG FOR THE RIDE.

LONG TERM...WEDNESDAY NIGHT THRU NEXT TUESDAY. 

00Z GFS ENSEMBLE MEAN CONTINUES TO INDICATE A QUIET AND COLD PATTERN 
SHAPING UP THROUGH THE WEEKEND BEFORE SOME MODERATION OCCURS EARLY 
NEXT WEEK.  WIDESPREAD RIDGING ACROSS THE ARCTIC WILL STILL LOOK TO 
DISPLACE THE POLAR VORTEX SOUTH OF ITS CLIMATOLOGICAL POSITION 
ACROSS SOUTHERN CANADA THROUGH THE WEEKEND.  THE RESULT WILL BE 
INTRUSIONS OF ARCTIC AIR INTO THE GREAT LAKES REGION.  LATEST 
OPERATIONAL MODEL RUNS ARE IN GOOD AGREEMENT THROUGH 12Z SATURDAY 
AND WILL USE A BLEND OF THE 06Z GFS AND 00Z ECWMF THROUGH THAT 
TIME.  THEREAFTER...HPC RECOMMENDS STICKING WITH THE MORE RELIABLE 
ECMWF...BUT WILL ALSO INCORPORATE SOME GFS ENSEMBLE MEAN IDEAS TO 
MITIGATE SOME OF THE DISCREPANCIES OF THE SMALLER SCALE FEATURES.

WEDNESDAY NIGHT...LOW PRESSURE WILL MOVE FROM LAKE HURON INTO SW 
QUEBEC...AND ANY WIDESPREAD SNOW WILL EXIT FAR NE WISCONSIN EARLY IN 
THE EVENING.  STILL SEEING PLENTY OF HIGH RH ALOFT WHICH COULD LEAD 
TO SCT SNOW SHOWER ACTIVITY DURING MUCH OF THE EVENING BEFORE 
TAPERING OFF OVERNIGHT.  THE BEST CHANCES FOR SEEING ACCUMULATING 
SNOW WILL BE ACROSS FAR N-C WISCONSIN WHERE 1000-850MB WINDS WILL BE 
OUT OF THE NW DIRECTION AND BE INITIALLY FAVORABLE FOR LAKE ENHANCED 
SNOW.  THESE WINDS WILL BE GRADUALLY BACKING AROUND DURING THE NIGHT 
WHICH SHOULD KEEP SNOWFALL TOTALS FAIRLY WELL BEHAVED.  WILL GO UP 
TO 2 INCHES OVER NORTHERN VILAS DURING THE EVENING AND AN ADDITIONAL 
INCH POSSIBLE OVERNIGHT.  OUTSIDE OF THE LAKE ENHANCED SNOW 
AREA...ACCUMULATIONS WILL BE MINOR...AND PROBABLY LESS THAN A HALF 
INCH.  WINDS WILL STILL BE GUSTY DURING THE EVENING HOWEVER...WITH 
GUSTS UP TO 30 MPH POSSIBLE AWAY FROM THE DOOR PENINSULA...WHERE 
SOME 40 MPH GUSTS COULD STILL OCCUR.  THIS WILL LEAD TO AREAS OF 
BLOWING AND DRIFTING SNOW CONTINUING DURING THE EVENING...REDUCING 
VSBYS TO A HALF MILE.  WINDS SLACKEN OFF SOMEWHAT AFTER 
MIDNIGHT...AND BLOWING AND DRIFTING SNOW WILL BECOME LESS OF A 
PROBLEM WITH TIME.  AS TEMPS FALL INTO THE SINGLE DIGITS LATE...THE 
BRISK WINDS ARE ANTICIPATED TO HELP WIND CHILL READINGS FALL TO NEAR 
-20F.

THURSDAY AND THURSDAY NIGHT...LOW PRESSURE WILL CONTINUE TO EXIT TO 
THE NORTHEAST ACROSS QUEBEC...BUT WILL SEE A TIGHT PRESSURE GRADIENT 
BETWEEN THIS LOW AND HIGH PRESSURE CENTERED OVER THE SOUTHEAST CONUS 
THAT WILL KEEP BRISK WESTERLY WINDS IN PLACE.  THESE WINDS WILL 
MAINTAIN THE ARCTIC AIRMASS IN PLACE OVER THIS 24 HOUR PERIOD WITH 
850MB TEMPS BETWEEN -18C AND -22C.  AFTER LOWS NEAR 0F...WILL NOT 
SEE TEMPS RISE VERY MUCH ON THURSDAY.  MAY SEE SOME SUNSHINE IN THE 
AFTERNOON AS CYCLONIC FLOW LOOSENS ITS GRIP BUT IT PROBABLY WONT 
HAVE MUCH IMPACT WITH THE BITTERLY COLD ARCTIC AIRMASS AND FRESH 
DEEP SNOWPACK IN PLACE.  HIGHS WILL RANGE FROM THE MIDDLE SINGLE 
DIGITS OVER N-C WISCONSIN TO THE LOWER TEENS NEAR LAKE MICHIGAN.  
EXPECT PARTLY CLOUDY SKIES THURSDAY NIGHT...BUT WILL STILL HAVE 
BREEZY CONDITIONS THAT WILL KEEP TEMPS FROM PLUMMETING.  LOWS IN THE 
SINGLE DIGITS BELOW ZERO. 

FRIDAY THROUGH TUESDAY...THE BITTERLY COLD AIRMASS RETREATS A BIT ON 
FRIDAY AS LOW LEVEL WINDS BACK AHEAD THE POLAR VORTEX DROPPING INTO 
THE LAKE WINNIPEG REGION.  HOWEVER...LOW INVERSION HEIGHTS AND A 
COLD START TO THE DAY WILL STILL MEAN TEMPS ONLY IN THE TEENS.  
RETURN FLOW STRENGTHENS FRIDAY NIGHT INTO SATURDAY AHEAD OF THE NEXT 
ARCTIC FRONT DUE TO CROSS THE AREA LATE SATURDAY AND SATURDAY 
NIGHT.  MODELS ARE MORE BULLISH WITH PRECIP CHANCES ALONG THE 
BOUNDARY...BUT UPPER LEVEL SUPPORT WILL REMAIN TO THE NORTH AND 
MOISTURE IS IN SUCH SCANT SUPPLY.  WILL KEEP THE AREA DRY...BUT THE 
TREND IS FOR BETTER CHANCES OF FLURRIES AND LIGHT SNOW.  ARCTIC HIGH 
PRESSURE THEN RETURNS ON SUNDAY INTO MONDAY.  COLDEST TEMPS LOOK TO 
REMAIN OVER CANADA HOWEVER.  THE NEXT SHORTWAVE IS PROGGED TO ARRIVE 
SOMEWHERE IN THE TUESDAY-WEDNESDAY TIMEFRAME...BUT PLENTY OF 
UNCERTAINTY AS WELL AS PROBABLE LOW IMPACT WILL LEAD ME TO KEEP THE 
AREA DRY.

AVIATION...MVFR CIGS AND IFR VSBYS SHOULD CONTINUE TO DETERIORATE
THROUGHOUT THE NIGHT AND WEDNESDAY MORNING. WINDS WILL ALSO
INCREASE SO ALL AIRPORTS WILL BE AFFECTED...AND MOST OR ALL
EVENTUALLY SHUT DOWN.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR WIZ013-
020>022-030-031-035>040-045-048>050-073-074.

WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR 
WIZ005-010>012-018-019.

&&

$$