Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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551 FXUS63 KGRB 081956 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 256 PM CDT Sat Jun 8 2024 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - Isolated thunderstorms possible rest of this afternoon north- central to northeast Wisconsin. Severe weather is not expected but stronger storms could produce gusty winds and small hail. Next chance for thunder is late Tuesday with greater chances on Thursday. - Chilly with potential for patchy frost over north-central Wisconsin late Sunday night. - Below normal temperatures through Tuesday with warm up following mid to late week. && .DISCUSSION... Issued at 254 PM CDT Sat Jun 8 2024 Short Term...Tonight and Sunday Main concern is extent and strength of storms into early this evening. Widespread showers from earlier have shifted east. Majority of forcing was tied to upper level jet, so rain amounts were generally less than 0.25 inch. Just as these showers are ending, approaching shortwave trough, steep low-level lapse rates and sfc trough working across Upper Michigan into northern Wisconsin is triggering a line of scattered showers and isolated storms. Report of half inch hail in western Upper Michigan and though the radar trends point to stronger convection only grazing far northeast WI, will have to watch if any stronger cells can shift into our area next few hours. After this band of showers and storms drops across, may see another shortwave pivot across northern WI bringing another round of isolated showers into early this evening. By late evening, convection will diminish as instability diminishes. A few light showers or sprinkles could make it to central and east-central WI late evening or early overnight. Otherwise, expect decreasing clouds and lows similar to what occurred this morning (40s north to mid 50s south and east). Sunday starts off partly sunny but it will quickly become cloudy from north to south. This as strong shortwave trough rotates just to the northeast and swath of H925-H7 moisture drops across the area. Soundings show some lift in this moist and weakly cyclonic flow, so kept small mention of showers but still no thunder over higher terrain of north-central. Some sprinkles may sneak south of that, but will be isolated. Temps will be the main story may only struggle into the lower 60s north before falling off some in the afternoon as cold air advection aloft shifts across from the north. Enough early day sunshine to boost readings into the upper 60s or near 70 elsewhere. Northwest winds will become breezy with gusts of 25 to 30 mph. Long Term...Sunday Night Through Saturday Temps and frost potential Sunday night and thunderstorm chances for the rest of the extended are main concerns. Clouds to begin early Sunday evening, but these will diminish through the night as high pressure and very dry airmass settles across (PWATs down to less than 0.25 inch). Winds likely go calm after midnight over northern WI which should allow temps to fall and open the door to frost potential. Lowered mins toward MOS guidance, though didn`t go as extreme as MET MOS at LNL which showed 32. Certainly possible if trends continue parts of the north may eventually need frost advisory. High pressure will then bring dry conditions Monday into Monday night. Dry trend will be short lived as approaching shortwave trough and cold front will result in next period of showers across the area on Tuesday. There is a narrow ribbon of return moisture surging ahead of the front, but instability looks minimal overall (MLCAPES well under 500J/kg) as the airmass only slowly recovers in wake of the early week high pressure/dry air. Only chances for thunder over the far west late aftn into the evening. Looks like we`ll have a dry day on Wednesday in this on again off again weather pattern, but Thursday holds a better chance for showers and some storms as another shortwave trough and stronger cold front arrive during peak heating. Timing differences in the guidance keeps pops at chance right now but eventually could see higher pops. If timing locks in more for the afternoon, possible that stronger storms could occur as stronger mid level winds arrive as instability builds up the best it is supposed to this week. Too early to start messaging this though given the uncertainty. During this time it appears temps rise to or even above normal with highs in the upper 70s to lower 80s. Beyond this, next better chance for showers and some storms would be late Friday into Saturday as this active pattern marches on. && .AVIATION...for 18Z TAF Issuance Issued at 1241 PM CDT Sat Jun 8 2024 Light rain and sprinkles over east-central terminals (GRB/ATW/MTW) will end by 19-20z. Local MVFR vsby/cigs but this will be only at the start of the TAF period. Otherwise, scattered to broken VFR cumulus will impact the region through late this afternoon in wake of the system. Isolated showers and possibly a storm could occur 19z-01z across northern WI, so have continued to mention VCSH at RHI. Skies become mostly clear tonight and start that way on Sunday before broken to overcast cloud cover spreads in by afternoon from the north with arrival of cooler air aloft. A light shower with brief MVFR conditions could form over north-central WI on Sunday afternoon, but conditions overall across the region will remain VFR. Northwest winds will become gusty later Sunday as well. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....JLA AVIATION.......JLA