FXUS63 KGRB 042100
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
300 PM CST FRI DEC 4 2009

.SYNOPSIS...LARGE SCALE PATTERN ACRS NOAM WL BE DOMINATED BY STG
RIDGE ALONG THE WEST COAST DURING THE FIRST PART OF THE FCST
PERIOD. THE RESULT WL BE FAIRLY DEEP DOWNSTREAM TROF ENCOMPASSING
MUCH OF THE CONUS. DURING THE LATTER PART OF THE PERIOD...RIDGE WL
BECOME SUBSTANTIALLY UNDERCUT BY BAND OF WESTERLIES FLOWING EWD
ACRS THE PAC. THAT WL LEAD TO FLATTENING OF THE TROF OVER THE
CONUS...WHICH WL LEAVE CONSIDERABLE UNCERTAINTY IN THE TIMING AND
TRACK OF FEATURES BY THE END OF THE FCST.

PCPN AMNTS FOR THE PERIOD WL HINGE ON THE EVOLUTION AND TRACK OF
THREE MAIN WX SYSTEMS. THE FIRST WL BE WITH WK WAVE RIDING NEWD IN
WSWLY UPR FLOW LATE IN THE WEEKEND. THE SECOND WL BE WHAT IS
LOOKING LIKE A MAJOR WINTER STORM MIDWEEK. THE FINAL IS ANOTHER
WEAKER SYSTEM AT THE END OF THE PERIOD. BEST GUESS IS THAT BTWN
THESE THREE SYSTEMS...PCPN AMNTS WL END UP ABV NORMAL FOR THE PERIOD.

THE WEST COAST RIDGE WL KEEP TEMPS NEAR OR A LITTLE BLO NORMAL
THROUGH MIDWEEK. A BRIEF SHOT OF VERY COLD AIR WL FOLLOW IN THE
WAKE OF THE MIDWEEK STORM. ASSUMING A SIG SNOW COVER IS
ESTABLISHED...THE FIRST BELOW ZERO NIGHTS OF THE YEAR WL BE
POSSIBLE. READINGS SHOULD MODERATE AFTER THAT AS FLOW BECOMES MORE
ZONAL AGAIN.
&&

.SHORT TERM...TNGT AND SAT. SHSN CONTD THIS AFTN...BUT THE
INTENSITY WAS NOT WHAT IT WAS THIS MORNING. THINK THE SHSN OVER
THE SE 1/2 OF THE FCST AREA WL CONT TO SLOWLY DECREASE. SERIES OF
UPPER LEVEL SHRTWVS ROTG BACK TOWARD N-C WI FM NRN MN/CAN SHOULD
RESULT IN SOMEWHAT ENHANCED SNOWFALL IN THAT AREA TNGT. STRUCTURED
FCST WITH HIGHEST POPS ACRS THE NW PART OF THE AREA. UPR HEIGHTS
SHOULD START TO RISE SAT AS THE FLOW ALOFT BEGINS TO BACK. THINK
THAT WL SHUT OFF MOST OF THE SHSN AND FLURRIES. WL JUST KEEP CHC
OF FLURRIES OVER N-C WI WHERE MODELS SHOW DEEPEST LINGERING
MOISTURE.

.LONG TERM...SATURDAY NIGHT THROUGH NEXT FRIDAY. MUCH MORE
INTERESTING WEATHER PATTERN FOR WISCONSIN NEXT WEEK AS TWO
SIGNIFICANT SYNOPTIC SCALE SYSTEMS FORECAST TO TRACK FROM THE
SOUTHERN PLAINS TO THE WESTERN GREAT LAKES. BEFORE THAT HAPPENS...
WAVE MOVING ALONG THE FRONT MAY BRING A LIGHT ACCUMULATING SNOW TO
THE SOUTHEAST HALF OF THE FORECAST AREA SUNDAY NIGHT AND MONDAY.
THE ECMWF AND NAM BRING THE 850MB LOW ACROSS SOUTHERN LAKE
MICHIGAN WITH AIR PLENTY COLD ENOUGH TO PRODUCE LAKE ENHANCEMENT.
THE GFS IS WEAKER, BUT WOULD STILL SUPPORT AT LEAST A LIGHT
SNOWFALL. SO WE RAISED THE CHANCES OF SNOW SUNDAY NIGHT INTO THE
LIKELY CATEGORY FOR THE FOX VALLEY AND LAKESHORE COUNTIES.

AFTER THAT...A STRONG (110KTS AT 500MB) JET LIFTS NORTHEAST FROM
THE SOUTHWESTERN UNITED STATES WHICH RESULTS IN CYCLOGENESIS IN
SOUTHEASTERN COLORADO EARLY TUESDAY. THE MODELS GENERALLY TAKE THE
SURFACE CIRCULATION ACROSS THE KANSAS OKLAHOMA BORDER ACROSS
MISSOURI AND CENTRAL ILLINOIS TO SOUTHERN LOWER MICHIGAN. THE
SURFACE SYSTEMS ARE NOT AS EXPLOSIVE AS EARLIER MODEL RUNS BUT
STILL LOOK SUFFICIENT TO PRODUCE A SIGNIFICANT SNOW ACROSS MOST OF
OUR FORECAST AREA. PRECIPITATION TYPE DOES NOT APPEAR TO BE AN
ISSUE AT PRESENT. INCREASED CHANCES OF SNOW TUESDAY NIGHT INTO THE
LIKELY CATEGORY AND LATER SHIFTS WILL PROBABLY DO THE SAME FOR
WEDNESDAY. BARRING A SIGNIFICANT SHIFT TO THE CURRENT TRACK WOULD
EXPECT A WINTER STORM WATCH TO BE ISSUED EITHER SUNDAY NIGHT OR
MONDAY FOR THIS SYSTEM.

ANOTHER SIGNIFICANT WAVE COMES OUT OF THE SOUTHWEST UNITED STATES
LATER IN THE WEEK WITH THE POTENTIAL FOR ACCUMULATING SNOWS AGAIN
FRIDAY NIGHT. THERE IS NOT AS MUCH COLD AIR AHEAD OF THIS SYSTEM
SO PRECIPITATION TYPE MIGHT BE AN ISSUE. WILL BE VAGUE ABOUT THAT
SYSTEM FOR NOW.
&&

.AVIATION...VIS STLT IMAGES SHOW CLDS QUITE THIN IN SPOTS...BUT
ALMOST ALL SFC OBS WERE OVC. GENERALLY MVFR CIGS PREVAILED ACRS
THE NW...WITH LOW-END VFR CIGS IN THE SE. THAT BASIC SITN SHOULD
PERSIST OVERNIGHT AND SAT...THOUGH THERE WL PROBABLY BE MORE
BREAKS IN THE CLDS BY SAT AFTN.
&&

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

$$
SKOWRONSKI/RDM