FXUS63 KGRB 101002
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
402 AM CST THU DEC 10 2009

.SYNOPSIS...UPR PATTERN ACRS NOAM STILL HIGHLY AMPLIFIED...WITH STG
RIDGE ALONG THE WEST COAST AND BROAD DOWNSTREAM TROF CENTERD OVER
THE N-C CONUS. TROF AXIS SHOULD BRIEFLY GET PULLED BACK INTO THE WRN
U.S. DURING THE WEEKEND AS INCREASINGLY STG SRN STREAM UNDERCUTS WRN
RIDGE AND LEADS TO MORE ZONAL FLOW ACRS THE CONUS. BUT AS FLOW AT
HIGH LATITUDES BECOMES INCREASINGLY BLOCKY AS A RESULT OF MASSIVE
RIDGE FORMING OVER THE NRN ATL...THE WESTERLIES ACRS THE CONUS WILL
HAVE LIMITED OPPORTUNITY TO AMPLIFY. THAT WL PROBABLY RESULT IN A
SERIES OF WEAK AND DIFFICULT TO TIME WX SYSTEMS CROSSING THE REGION.

SHOT OF COLD AIR DRIVEN INTO THE FCST AREA IN THE WAKE OF YESTERDAYS
MEGA-SNOWSTORM...COMBINED WITH FRESH DEEP SNOWCOVER...WL KEEP TEMPS
WELL BELOW NORMAL FOR A COUPLE DAYS. TEMPS SHOULD THEN REBOUND. MED
RANGE MODELS HAVE BACKED AWAY SOME FM SIG BLAST OF COLD AIR NEXT
WK...AND INSTEAD LEAVE FCST AREA NR SRN EDGE OF COLD AIR MASS WITH
TEMPERATURES LIKELY OSCILLATING UP AND DOWN AS COLD AIR SURGES
SWD AND THEN RETREATS NWD WITH THE PASSAGE OF EACH SYSTEM. WK
SYSTEMS RIDING ALONG EDGE OF COLD AIR MASS WL PROBABLY GENERATE
SOME LGT SNOW AT TIMES...BUT PCPN AMNTS WL PROBABLY END UP BEING
LOW.
&&

.SHORT TERM...TDA/TNGT/FRI. COLD AIR WAS INITIALLY SLOW TO SURGE EWD
INTO THE AREA...BUT IT/S ARRIVING NOW. TEMP FCST ALL 3 PERIODS VERY
TRICKY. IT/S NOT HELPED BY THE FACT THAT STATISTICAL GUID PROBABLY
DOES NOT FULLY ACCOUNT FOR NEW DEEP SNOWCOVER. NORMALLY USEFUL BIAS-
CORRECTED GUIDANCE VERY SUSPECT BECAUSE AFTER ALL THE WARM WX THE
PAST MONTH...BC VALUES WOULD BE EXTRAPOLATIONS OFF THE END OF
REGRESSION CURVE. OVERALL...MAV/GRIDDED MOS SEEMED WAY TOO WARM. MET
PROBABLY BETTER. OVERALL APPROACH WAS TO TREND COLDER THAN GUID IN
MOST INSTANCES.

NOT ANTICIPATING MUCH RECOVERY IN TEMPS TDA. WIND CHILL ADVISORY IN
EFFECT UNTIL 15Z. MAY FLIRT WITH ADVISORY CRITERIA ALL DAY IN
CENTRAL WI...BUT AT THIS POINT JUST PLANNING TO LET ADVISORY EXPIRE.

OF THE 3 FCST PERIODS...TEMPS TNGT PROBABLY THE TOUGHEST. AIR
MASS ITSELF IS QUITE COLD. GIVEN THE SNOWCOVER...IF ANY SITE
MANAGES TO DECOUPLE WHILE SKIES ARE CLEAR...EVEN FOR AN HOUR OR
TWO...IT COULD JUST PLUMMET TO 20 OR 25 BELOW ZERO (LNL...Y50...
TKV...AND RRL MAKE ME ESPECIALLY NERVOUS). BUT OVERALL...THERE
SHOULD BE ENOUGH WIND TO HOLD TEMPS UP SOME SO WENT WITH THAT IDEA
IN THE FCST. WL ALMOST CERTAINLY NEED ANOTHER WIND CHILL
ADVSIORY...PROBABLY FOR THE WHOLE AREA. BUT WL HOLD OFF ISSUING
THAT NOW SINCE WE ALREADY HAVE ONE FOR THIS MORNING. JUST GOING
WITH ADVISORY CRITERIA WIND CHILLS IN THE GRIDS/ZONES AND MENTION
IN HWO SHOULD SUFFICE FOR NOW.

FRI...DON/T SEE MUCH REASON TO WARM A WHOLE LOT MORE THAN WHAT WE
DO TDA DESPITE MOST OF GUID TEMPS RUNNING RATHER SUBSTANTIALLY
WARMER THAN TDA. ONCE AGAIN...TRENDED COLDER THAN GUID IN FCST.

WITH FAIRLY STG BAROCLINIC ZONE IN PLACE ACRS THE AREA...THERE WL BE
CLOUDS COMING ACRS FM TIME TO TIME AND IT WON/T BE VERY HARD TO
GENERATE FLURRIES. BUT AFTER 10-15 INCHES OF SNOW ACRS PRETTY MUCH
THE WHOLE AREA YESTERDAY...DIDN/T REALLY SEE THE POINT IN CARRYING
PROLONGED PERIOD OF CHC OF FLURRIES. WL MAINTAIN SCT FLURRIES FOR
STUFF MOVG THROUGH THIS MORNING...BUT LEAVE OUT OF THE OTHER
PERIODS FOR NOW. CAN ALWAYS BE ADDED IN LATER IF NEEDED.

.LONG TERM...FRIDAY NIGHT THROUGH NEXT THURSDAY. UPPER FLOW
BECOMES ZONAL FRIDAY NIGHT AND SATURDAY. AT THE SURFACE COLD HIGH
SHIFTS OFF TO THE EAST SETTING UP A BROAD WARM ADVECTION PATTERN
ACROSS OUR AREA. CLOUDINESS SHOULD INCREASE LATE FRIDAY NIGHT AND
SATURDAY BUT HELD OFF ON ANY LIGHT SNOW OR FLURRIES UNTIL SATURDAY
NIGHT AND SUNDAY WHEN A WEAK SHORTWAVE TROUGH APPROACHES FROM THE
CENTRAL PLAINS. RAISED MINIMUMS SATURDAY NIGHT AND HIGHS SUNDAY AS
925MB TEMPERATURES CLIMB INTO LOW SINGLE NUMBERS BELOW ZERO.

EXPECT SOME LIGHT PRECIPITATION SUNDAY NIGHT AND MONDAY AS SURFACE
TROUGH MOVES ACROSS THE REGION. BOUNDARY LAYER TEMPERATURES SHOULD
BE NEAR FREEZING SO THINK IT SHOULD BE SNOW BUT A LITTLE SLEET OR
FREEZING DRIZZLE POSSIBLE DEPENDING ON HOW WARM IT GETS BETWEEN
925MB AND 850MB AND WHETHER THERE ARE ADEQUATE ICE FORMING
NUCLEII FOR SNOW. AFTER THAT TROUGH GOES BY MORE ARTIC AIR COMES
DOWN INTO THE PLAINS STATES FOR THE MIDDLE OF THE WEEK THOUGH IT
DOESN/T LOOK QUITE AS COLD AS THE LAST FEW MODEL RUNS.
&&

.AVIATION...EXPECT MAINLY VFR CONDITIONS DURING THE PERIOD. CIGS
COULD CREEP DOWN INTO MVFR CATEGORY AT TIMES...ESPECIALLY OVER N-C
WI.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 10 AM CST THIS MORNING FOR WIZ030-031-
035>038-045-048-049.

&&

$$
SKOWRONSKI/RDM