Issued by NWS Green Bay, WI
000 FXUS63 KGRB 071113 AFDGRB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREEN BAY WI 513 AM CST FRI NOV 7 2008 .SHORT TERM...TODAY THROUGH SATURDAY STACKED LOW PRESSURE SYSTEM CENTERED NEAR SOUTHWEST MINNESOTA EARLY FRIDAY MORNING FORECAST TO SLOWLY MOVE NORTHEAST ACROSS NORTHERN WISCONSIN NEXT 24 TO 36 HOURS. THIS SYSTEM WILL CONTINUE TO BE THE FOCUS OF SHOWERY PRECIPITATION IN THE SHORT-TERM. DRY SLOT ASSOCIATED WITH THE OCCLUDED SYSTEM STILL PERSISTING OVER THE EASTERN HALF OF WISCONSIN EARLY THIS MORNING. HOWEVER...EXTENSIVE CLOUD COVER AND SCATTERED PRECIPITATION SLOWLY WORKING ITS WAY EASTWARD ACROSS WESTERN INTO CENTRAL WISCONSIN. AFTER SOME MORNING SUN...EXPECT SKIES TO BECOME CLOUDY ACROSS THE EAST AS THE MORNING PROGRESSES. WATER VAPOR IMAGERY SHOWS A COUPLE IMPULSES ROTATING AROUND THE UPPER LOW. THE FIRST IMPULSE NOW WORKING ITS WAY NORTHWARD ACROSS CENTRAL WISCONSIN. JUST A FEW WIDELY SCATTERED LIGHT SHOWERS ASSOCIATED WITH THIS FEATURE. CONSIDERABLY MORE POTENT IMPULSE LOCATED OVER SOUTHWEST MINNESOTA FORECAST TO EVENTUALLY SWING EASTWARD ACROSS SOUTHCENTRAL WISCONSIN BY 06Z SATURDAY. THIS FEATURE WILL BE THE IMPETUS FOR MORE WIDESPREAD PRECIPTATION AS IT APPROACHES THE AREA LATER TODAY. IN FACT RADAR IMAGERY SHOWS WELL- ORGANIZED AREA OF LIGHT SNOW OVER SOUTHERN MINNESOTA...WITH A MIX OF RAIN AND SNOW SHOWERS FURTHER EAST OVER SOUTHWEST WISCONSIN. MODELS APPEAR TO BE IN FAIRLY GOOD AGREEMENT IN BRINGING THE PRECIPITATION INTO THE WESTERN PORTION OF THE FORECAST AREA LATER THIS MORNING...THEN ACROSS THE REMAINDER OF THE FORECAST AREA DURING THE AFTERNOON. FORECAST SOUNDINGS SUGGEST BOUNDARY LAYER TEMPS WILL SUPPORT MAINLY RAIN OVER THE EAST AND MIXTURE OF RAIN AND SNOW ACROSS CENTRAL WISCONSIN TODAY. AS COLDER AIR CONTINUES TO WRAP AROUND THE SYSTEM TODAY...EXPECT PRECIPITATION TO GRADUALLY CHANGE OVER TO SNOW ESPECIALLY OVER CENTRAL SECTIONS OF THE FORECAST AREA LATER TODAY INTO THE EVENING. FEEL BOUNDARY LAYER WILL STILL BE A BIT TOO WARM OVER THE EAST...THUS MORE OF A RAIN/SNOW MIX OVERNIGHT THERE. SHOWERY NATURE OF THE PRECIPTATION WILL CONTINUE OVERNIGHT TONIGHT AND THROUGH MUCH OF SATURDAY. AGAIN BEST CHANCE FOR SEEING SOME LIGHT ACCUMULATIONS WOULD BE MAINLY OVER CENTRAL AND NORTHERN SECTIONS OF THE FORECAST AREA AS UPPER LOW DRIFTS OUT OVER LAKE MICHIGAN BY AROUND 18Z. COLD AIR ADVECTION NORTHWEST THE DEPARTING SYSTEM WITH AMPLE BOUNDARY LAYER MOISTURE AND FAVORABLE FETCH SUGGESTS LES POTENTIAL FOR VILAS COUNTY MAINLY LATE SATURDAY INTO SATURDAY NIGHT. .LONG TERM...SATURDAY NIGHT THROUGH THURSDAY UPPER LOW CONTINUES TO MOVE SLOWLY AWAY FROM WISCONSIN SATURDAY NIGHT AND SUNDAY. UPPER LEVEL DISTURBANCES WILL ROTATE AROUND THE UPPER LOW THROUGH SUNDAY...BRINGING A CHANCE OF SNOW SHOWERS TO THE REGION. WILL ALSO NEED TO WATCH LAKE EFFECT POTENTIAL SATURDAY NIGHT THROUGH SUNDAY AS 850MB TEMPERATURES DROP TO -10 C BY SUNDAY AFTERNOON. LAKE TO 850MB TEMPERATURE DIFFERENCES OF 19 C NOTED WITH A FAVORABLE WIND TRAJECTORY OF 330 TO 340 DEGREES SATURDAY NIGHT. LOOKING AT THE LAKE EFFECT FLOW CHART... 1 TO 3 INCHES OF SNOW CAN BE EXPECTED SATURDAY WITH SOME POTENTIAL FOR HEAVIER SNOW TOTALS OVER NORTHERN VILAS COUNTY. SOME DIFFERENCES IN THE MODEL WIND DIRECTION AT 850MB ON SUNDAY AHEAD OF NEXT SHORTWAVE THAT WILL MOVE ACROSS WISCONSIN DURING THE DAY SUNDAY. ECMWF/GFS INDICATING A MORE FAVORABLE DIRECTION THAN THE WRF. ONLY WENT WITH A HIGH CHANCE FOR SNOW SHOWERS ACROSS VILAS COUNTY DUE TO THE UNCERTAINTY OF WINDS AROUND 850MB. THE SHORTWAVE WILL PASS EAST OF WISCONSIN SUNDAY NIGHT...BRINGING PARTLY CLOUDY SKIES AND SEASONABLY COLD FOR THIS TIME OF YEAR. CONTINUED A SMALL CHANCE OF SNOW SHOWERS OVER THE FAR NORTH. NEXT SYSTEM WILL PASS SOUTH OF WISCONSIN ACCORDING TO ECMWF ON TUESDAY AND TUESDAY NIGHT. OPERATIONAL GFS SUPPORTS A MORE NORTHERN SOLUTION WHICH WOULD BRING PRECIPITATION INTO THE SOUTHERN PORTION OF THE FORECAST AREA. GFS 6 HOUR QPF ENSEMBLE MEMBERS INDICATED A FEW MEMBERS AGREE WITH THE THE OPERATIONAL GFS...WHILE MOST OF THE REST OF THE ENSEMBLE MEMBERS KEPT US DRY AND DISAGREED STRONGLY WITH THE OPERATIONAL GFS. SINCE THERE IS NOT OVER WHELMING SUPPORT TO INCLUDE PRECIPITATION ON TUESDAY AND TUESDAY NIGHT...WILL LEAVE THESE PERIODS DRY FOR NOW AND MONITOR LATER MODEL RUNS. IT SHOULD BE NOTED THAT THE GFS/ECMWF DO TRY TO BRING PRECIPITATION OFF LAKE MICHIGAN DURING THIS TIME FRAME AS WELL. AS 850MB TEMPERATURES RELATIVELY COLD. LITTLE CHANGES MADE TO THE REMAINDER OF THE FORECAST. && .AVIATION...GENERALLY IFR CONDITIONS EARLY THIS MORNING FOR EASTERN WISCONSIN WITH CLOUDS AND SCATTERED RAIN AND SNOW SHOWERS SPREADING EAST ACROSS THE FORECAST AREA DURING THE DAY. EXPECT WIDESPREAD MVFR CONDITIONS BY FRIDAY AFTERNOON ESPECIALLY WITH HEAVIER RA/SN SHOWER ACTIVITY. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ ESB/ECKBERG
