000
FXUS63 KGRB 092048
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
248 PM CST MON DEC 9 2013

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 247 PM CST MON DEC 9 2013

LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW A BROAD AREA OF
LOW PRESSURE MOVING NORTHEAST OVER NORTHERN ONTARIO AND A SURFACE
RIDGE AXIS SHIFTING EAST OVER THE NORTHERN PLAINS.  BETWEEN THE TWO
SYSTEMS...WEST WINDS IS DRIVING ARCTIC AIR ACROSS THE STATE...AND
TEMPERATURES ARE DROPPING ACROSS CENTRAL AND NORTH-CENTRAL
WISCONSIN.  NO CHANGE IN THE START OF TIME OF WIND CHILL
HEADLINES...AS THEY ARE ALREADY APPROACHING CRITERIA AT RHINELANDER.
THE LEADING EDGE OF THIS ARCTIC AIR IS MARKED BY A BAND OF STRATO-CU
AND ACCOMPANYING LIGHT SNOW SHOWERS/FLURRIES...WHICH IS NOW ENTERING
NORTHEAST WISCONSIN.  ANTICIPATE THE SNOW SHOWERS/FLURRIES TO
DIMINISH LATER THIS AFTERNOON ONCE THE SUN GOES DOWN AND ANY DIURNAL
INSTABILITY IS LOST.  ATTENTION THEN TURNS TO A FAST MOVING CLIPPER
SYSTEM WHICH IS DIVING SE OVER SOUTHERN SASKATCHEWAN THIS
AFTERNOON.  THE CLIPPER LOOKS DECENT ON SATELLITE IMAGERY AND THERE
ARE PLENTY OF OBS OVER WESTERN NORTH DAKOTA AND EASTERN MONTANA
SHOWING LIGHT TO MODERATE SNOW.  SO THE FORECAST CONCERNS START OUT
WITH WIND CHILLS TONIGHT...AND SNOW POTENTIAL WITH THE CLIPPER LATE
TONIGHT INTO TUESDAY MORNING.

TONIGHT...HIGH PRESSURE RIDGE AXIS WILL MOVE EAST INTO CENTRAL
WISCONSIN THIS EVENING AND ACROSS EASTERN WISCONSIN OVERNIGHT.
ALONG WITH THE LOSS OF DAYTIME HEATING...THIS WILL HELP SKIES CLEAR
AND LIGHT SNOW/FLURRIES COME TO AN END LATE IN THE AFTERNOON OR
EARLY THIS EVENING.  ARCTIC AIR WILL CONTINUE TO POUR ACROSS THE
REGION DURING THE EVENING...AND THE CLEARING SKIES WILL PROMOTE
TEMPS FALLING QUICKLY WITH LOWS OCCURRING NEAR OR SHORTLY AFTER
MIDNIGHT.  THEN ALL EYES WILL BE ON A FAST MOVING CLIPPER PROGGED TO
ENTER THE STATE LATE TONIGHT.  THE LATEST MODEL RUNS HAVE TRENDED A
FEW HOURS SLOWER...AND NOW START BRINGING IT INTO THE STATE AFTER
09Z.  THE VORT WILL BRING EXCELLENT MID-LEVEL FORCING...SO WILL
INCREASE POPS BY 12Z DESPITE A SEVERE LACK OF MOISTURE.  WITH THE
LATER ARRIVAL OF THE CLIPPER...WIND CHILL READINGS WILL REMAIN NEAR
THE 20 BELOW CRITERIA OVER CENTRAL AND NORTH-CENTRAL WISCONSIN
THROUGH THE 12Z HOUR SO NO CHANGE IN HEADLINES ANTICIPATED.  TEMPS
WILL REBOUND SOMEWHAT WITH THE INCREASING CLOUDS OVERNIGHT.

TUESDAY...THE CLIPPER WILL QUICKLY ADVANCE EAST ACROSS THE AREA
TUESDAY MORNING.  THE STRONG FORCING AND POCKET OF INSTABILITY IN
THE MID-LEVELS SHOULD BRING A FEW TENTHS OF DRY FLUFFY SNOW ACROSS
THE ENTIRE FORECAST AREA BEFORE IT RAPIDLY PULLS OUT BY LATE IN THE
MORNING OR EARLY AFTERNOON.  ANOTHER SURGE OF ARCTIC AIR WILL FOLLOW
IN THE WAKE OF THE CLIPPER...WITH STEEPENING LOW LEVEL LAPSE RATES
AND ENHANCED LOW LEVEL RH.  WOULDNT BE SURPRISED TO SEE INSTABILITY
SNOW SHOWERS/FLURRIES REDEVELOP IN THE AFTERNOON...SIMILAR TO THE
SNOW SHOWERS ONGOING TODAY.  WILL LET THE NEXT SHIFT EVALUATE BEFORE
ADDING THEM TO THE FORECAST.  HIGHS FROM THE MIDDLE SINGLE DIGITS
NORTH TO THE MIDDLE TEENS EAST.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 247 PM CST MON DEC 9 2013

COLD TEMPERATURES/WIND CHILLS AND PCPN CHANCES ARE THE MAIN FCST
CONCERNS.

A REINFORCING SHOT OF ARCTIC AIR WILL BE IN PLACE TUES NGT INTO
WEDS...WITH H8 TEMPS OF -20 TO -25 C OVER THE FORECAST AREA. LOW-
LEVEL WINDS WILL BE WEST-NORTHWEST...SO LAKE EFFECT IMPACT WILL BE
MINIMAL...WITH JUST A FEW SNOW SHOWERS OR FLURRIES EXPECTED OVER
VILAS COUNTY. A S/W TROF AND THE RRQ OF A JET STREAK WILL QUICKLY
SWEEP THROUGH THE SOUTHERN PART OF GRB CWA ON TUES NGT...SO KEPT
CHC POPS OVER C/EC WI. CLOUDS ASSOCIATED WITH THIS SYSTEM AND ANY
LAKE-INDUCED CLOUDS OVER THE FAR NORTH COULD HAVE A BIG IMPACT ON
MIN TEMPS. USED A BLEND OF THE PREV FCST...ECMWF AND A FEW OTHER
TOP PERFORMING GUIDANCE SETS...AND MADE A FEW TWEEKS TO ACCOUNT
FOR CLOUD TRENDS. WILL HAVE COLDEST MIN TEMPS (-15 TO -17 F) IN
THE TOMAHAWK/RHINELANDER/CRANDON REGION...WITH SINGLE DIGITS
BELOW ZERO OVER OUR SOUTHERN/EASTERN COUNTIES...EXCEPT SINGLE
DIGITS ABOVE ZERO ALONG THE LKSHR. HIGH TEMPS ON WEDS WILL BE IN
THE 5 BELOW TO 5 ABOVE RANGE IN MOST AREAS...COLDEST OVER NC WI.
WIND CHILLS LOOK LIKE THEY WILL DROP INTO THE -20 TO -30 RANGE
NORTHWEST OF A LINE FROM ISW-IMT TUES NGT INTO WEDS...AND OVER
MOST OF THE CWA ON WED NGT...SO ADDITIONAL WIND CHILL ADVISORIES
MAY BE NEEDED.

WAA WILL DEVELOP LATE WEDS NGT INTO THURSDAY...AND WILL PROBABLY
GENERATE SOME LIGHT SNOW OR FLURRIES. SOME MODERATION IN TEMPS
IS ANTICIPATED...WITH HIGHS REACHING THE UPPER SINGLE DIGITS
AND TEENS.

THE ARCTIC BAROCLINIC ZONE WILL RESIDE OVER THE REGION THROUGH
MUCH...IF NOT ALL...OF THE EXTENDED FORECAST. TEMPERATURES
WILL REMAIN BLO NORMAL. WITH STRONG WEST-NORTHWEST FLOW ALOFT
IN PLACE DURING THE PERIOD...SEVERAL JET STREAKS/SHORT-WAVE TROFS
WILL PASS THROUGH THE GREAT LAKES REGION. THE RRQ OF A JET STREAK
WILL PASS THROUGH THE REGION THU NGT AND FRI...AND MODELS ARE
HINTING AT AN INVERTED SFC TROF AFFECTING THE REGION FRI NGT/SAT...
AND POSSIBLY LINGERING OVER THE RGN INTO SUNDAY. ANY OF THESE
DISTURBANCES COULD PRODUCE LIGHT SNOW OR FLURRIES...SO ALMOST
EVERY PERIOD OF THE FCST HAS SLGT CHC/CHC POPS. HOPEFULLY IN THE
NEXT FEW DAYS WE WILL BE ABLE TO BETTER DEFINE WHICH OF THESE
SYSTEMS WILL HAVE THE MOST IMPACT ACROSS THE REGION.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1128 AM CST MON DEC 9 2013

LIGHT SNOW AND FLURRIES ARE STUBBORNLY STICKING AROUND
CENTRAL AND NORTH-CENTRAL WISCONSIN AT MIDDAY...AND HAVE TO EXTEND
LOWER VSBYS IN LIGHT SNOW INTO MID-AFTERNOON.  WEST WINDS WILL ALSO
REMAIN GUSTY THROUGH THE AFTERNOON BEFORE THE GUSTINESS SUBSIDES BY
EARLY THIS EVENING.  A PERIOD OF VFR CONDITIONS WILL THEN FOLLOW
UNTIL LATE TONIGHT...AND THEN A FAST MOVING CLIPPER TYPE SYSTEM WILL
BRING A QUICK ROUND OF SNOW AND LOWERING CIGS LATE TONIGHT INTO
TUESDAY MORNING.  VSBYS IN THE SNOW TO AT LEAST FALL INTO THE IFR
RANGE...AND POSSIBLY LOWER BASED ON OBSERVATIONS OVER MONTANA.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WIND CHILL ADVISORY UNTIL 6 AM CST TUESDAY FOR WIZ005-010>013-
018>021-030-031-035>037.
&&

$$

SHORT TERM.....MPC
LONG TERM......KIECKBUSCH
AVIATION.......MPC