FXUS63 KGRB 200756
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
256 AM CDT SAT SEP 20 2008
.SHORT TERM...TODAY/TONIGHT/SUNDAY. A COLD FRONT OVER FAR NW WI
EARLY THIS MORNING WILL CONTINUE TO SLIDE SOUTH OVER THE FORECAST
AREA TODAY. WEAK RADAR RETURNS WERE NOTED IN THE INSTABILITY AXIS
AHEAD OF THE SURFACE COLD FRONT AND ALONG THE H8 FRONT.  MODELS
PROG THIS INSTABILITY AXIS TO CONTINUE TO SHIFT SLOWLY SOUTH TODAY
BEFORE DEPARTING INTO SRN WI AS THE COLD FRONT DROPS SOUTH OF THE
REGION. DUE TO ONGOING BUT SPARSE ACTIVITY ON THE RADAR WILL
CONTINUE WITH THE SMALL MENTION OF CONVECTION TODAY.
NEXT FORECAST ISSUE DEALS WITH TEMPS TONIGHT AS THE COOL HIGH
PRESSURE SYSTEM DRIFTS OVER THE GREAT LAKES REGION. COLDEST TEMPS
IN THE CENTER OF THE HIGH PASSES WELL NORTHEAST OF THE AREA
TONIGHT BUT ADVECTION OF DRIER AND COOLER TEMPS OVER THE NORTH
COMBINED WITH A FEW HOURS OF LIGHTS WINDS DURING THE LONGER NIGHTS
ALLOWS A CHANCE OF FROST DEVELOPMENT OVER THE FAR NORTH. COORD
WITH MQT FOR FROST/FREEZE HEADLINES NORTH.
WILL KEEP THE SUNDAY PORTION DRY DUE TO THE PERSISTENT DRY EASTERLY
FLOW FROM THE SURFACE HIGH. BUT DID NOTE THE RELATIVELY UNSTABLE
AIR MASS RETURNING QUICKLY NORTHWARD OVER AREAS TO THE WEST.
.LONG TERM...SUNDAY NGT THRU NXT FRI. MAIN FCST CHALLENGE REMAINS
TIMING OF PCPN TOWARD THE MIDDLE OF NXT WEEK AS A CDFNT APPROACHES
THE RGN.
A WEAK UPR RDG AXIS TO RESIDE OVR THE WRN GREAT LKS SUNDAY NGT
WITH VARIOUS LVL OF MSTR LINGERING OVR THE RGN AS SEEN ON FCST
SNDNGS. SOUTHERLY BNDRY LYR WNDS WL PREVAIL OVR WI AS SFC HI PRES
CONTS TO SLOWLY PULL EAST INTO SW SECTIONS OF QUEBEC. NO TRIGGER
OR FOCUSING MECHANISM PRESENT...THUS A DRY NGT EXPECTED WITH SKY
CONDITIONS RANGING FROM MOSTLY CLR TO MOSTLY CLDY AT TIMES. HAVE
SPLIT THE DIFFERENCE AND GONE PARTLY CLDY FOR THE MOST PART. ANY
CLEARING COMBINED WITH LGT WNDS MAY ALLOW FOR SOME PATCHY FOG TO
DVLP ESP AFT MIDNGT AND HAVE ADDED THIS POTENTIAL TO THE FCST.
THE UPR RDG REMAINS OVR THE GREAT LKS ON MON...BUT A LEAD SHRTWV
TROF EJECTING NEWD INTO THE UPR MIDWEST AHD OF THE MAIN UPR TROF
LOCATED IN THE ROCKIES WL BRING MORE CLDS TO WI. A 40 KT LOW LVL
JET IS ALSO AIMED AT THE UPR MIDWEST AND WL IMPROVE MSTR
TRANSPORT...Q-VEC CONVERGENCE...AS WELL AS BETTER INSTABILITY TO
CREATE SHWRS AND TSTMS. THIS ACTIVITY WL REMAIN TO OUR WEST...
HOWEVER WOULD NOT BE SURPRISED TO SEE AN ISOLATED SHWR OR TSTM
APPROACH CNTRL WI BY LATE IN THE DAY. TEMPS WL BE ON THE RISE ON
MON THANKS TO THOSE PERSISTENT SOUTH WND ALOFT. 
THIS SHRTWV TROF CONTS TO LIFT NE THRU THE REST OF THE UPR MIDWEST
AND INTO SW ONTARIO MON NGT. BULK OF FORCING/DYNAMICS/INSTABILITY
REMAIN LOCKED WITH THE TROF...THUS RAISING THE QSTN OF HOW FAR
EAST CAN ANY PCPN GET INTO WI? N-CNTRL WI WOULD BE THE MOST
SUSCEPTIBLE AND THE NAM AND SREF DO BRING LGT PCPN INTO THIS PART
OF THE FCST AREA. HOWEVER...WITH ALL THE PERTINENT INGREDIENTS
FOCUSED TO OUR WEST...PREFER TO KEEP THE FCST DRY. HAVE RAISED MIN
TEMPS A COUPLE OF DEGS OVR INLAND LOCATIONS AS WAA/SOME INCREASE
IN CLDS HOLD READINGS UP.
AS THE UPR RDG SHIFTS EAST INTO THE ERN GREAT LKS ON TUE...THIS
ALLOWS FOR THE MAIN UPR TROF TO MOV INTO/ACROSS THE NRN PLAINS. AN
ATTENDANT CDFNT WL PRECEDE THE UPR TROF AND IS PROGGED TO PUSH
INTO MN BY TUE AFTERNOON. MSTR CONVERGENCE/LIFT ALONG THE FNT
SHOULD COMBINE WITH INCREASED INSTABILITY...FORCING AND ADDL LIFT
FROM THE RGT ENTRANCE RGN OF THE UPR JET...TO PRODUCE SHWRS/TSTMS
WITH AN EWD MOVEMENT INTO WI. AFT COLLABORATION WITH DLH AND MQT...
HAVE DECIDED TO ADD A SLGT CHC POP TO N-CNTRL AND CNTRL WI TUE
AFTERNOON. A WARM DAY ON TAP WITH MAX TEMPS IN THE 70S (COOLER
NEAR THE LAKE).
SINCE THE BEST UPR SUPPORT SHIFTS INTO ONTARIO TUE NGT INTO WED...
THE CDFNT IS EXPECTED TO MAKE ONLY A SLOW SE MOV INTO THE WRN
GREAT LKS. THE GFS MAINTAINS A STRONGER UPR TROF...THEREBY
ALLOWING THE FNT TO "FLY" THRU WI ON WED. PREFER THE SLOWER SOLN
SIMILAR TO THE ECMWF AND CANADIAN WHICH GRADUALLY INCREASES PCPN
CHCS ACROSS NE WI. EXPECT WRN SECTIONS OF THE FCST AREA TO HAVE
SHOT OF SEEING MEASURABLE PCPN...THUS HIGHER POPS PLACED THERE.
DO NOT SEE THE CDFNT GETTING TOO FAR INTO WI WED NGT (THRU NRN WI
INTO CNTRL WI) AS THE FNT BECOMES PARALLEL WITH THE MEAN FLOW
ALOFT. AS LONG AS THIS BNDRY REMAINS IN OUR VCNTY...HAVE NOT
CHOICE BUT TO CONT RUNNING A LOW END POP IN THE FCST FOR WED NGT
INTO THU. THERE ARE INDICATIONS THAT THE FNT MAY LIFT BACK NORTH
BY FRI...BUT WITH ANOTHER CDFNT PROGGED TO APPROACH THE RGN...
PREFER TO LEAVE A MINOR POP IN THE FCST FOR FRI.
&&
.AVIATION...REGION OF LLWS TO AFFECT AREAS SOUTH OF A LINE FROM
AUW TO GRB UNTIL AROUND 15Z THIS AM. MAINLY VFR CONDITIONS
EXPECTED TODAY AND TONIGHT...WITH THE EXCEPTION OF ISOLD MVFR CIGS
AND VSBYS DUE TO CONVECTION TODAY. PATCHY AREAS OF MVFR TO IFR
VSBYS DUE TO FOG IS POSSIBLE OVERNIGHT OVER NRN WI INCLUDING RHI.
&&
.MARINE...ONE SCA WILL BE DROPPED EARLY THIS MORNING...HOWEVER
DEVELOPING AND PERSISTENT NORTHEAST TO EAST WINDS ALONG THE LAKE
MICH SHORELINE TONIGHT INTO SUNDAY WITH THE CAA WILL INCREASE
WAVE ACTIVITY. ANOTHER SCA WILL BE ISSUED FOR TONIGHT INTO SUNDAY.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY FROM 3 AM TO 7 AM CDT SUNDAY FOR WIZ005-010>013.
&&
$$
TH/AK