Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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536 FXUS63 KGRB 292341 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 641 PM CDT Sat Jun 29 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Conditions hazardous to small craft are possible into Sunday morning, then again Tuesday and Tuesday night. - Some rivers and streams will remain above bankfull through much of next week. - The next period to watch for heavy rain and stronger storms will be late Monday night through Tuesday night. && .DISCUSSION... Issued at 254 PM CDT Sat Jun 29 2024 A few showers and storms into early this evening, then dry through Monday. We remain in a very active pattern though so the next chance for rain, possibly heavy, returns late Monday night through Tuesday night. Some risk of strong or severe storms late Tuesday as well. Late afternoon into Tonight...Currently the tail of sharp pinwheeling shortwave trough north of Lake Superior is combining with MLCAPES up to 1000J/kg to generate cluster of thunderstorms over eastern Upper Michigan. Isolated storms have tried to fill in farther southwest across Bay of Green Bay and Door County, but so far, these storms have had a hard time organizing. Perhaps this is due to very weak mid-level lapse rates which are farther north across Upper Michigan/Lake Superior. Re-enforcing cold front tied to another sharp shortwave dropping across ND/western MN with some punch is moving over northwest WI. Sharp wind shift noted and temps upstream over MN are in the 50s. No instability for the front to work with though, so though spotty showers may impact much of central to north- central WI once the front moves through, looks like we`ll be clear from any additional thunder threat. NW- NNW winds will be gusty all areas in wake of the front. Temps will take a tumble with readings by daybreak into the upper 30s/near 40 over the northwoods. Sunday and Sunday night...Winds diminish on Sunday and we should see wall-to-wall sunshine. Nice early summer day, though for some it will probably be too cool with highs topping out low to mid 70s inland and mid to upper 60s near Lake Michigan. High pressure settles across Sunday night. Light winds, clear skies and PWAT down to 0.4 spell a chilly night over north-central WI, by spring, or summer standards. MET guidance for LNL is 35. Could see favored cold spots into the mid to upper 30s. Monday through Tuesday...High shifting east and approaching deep mid- level trough from south central Canada to the northern Plains will bring strong return flow to the area Monday night into Tuesday. Mid- level jet and PWAT surging to 1.8 to 2.0 inches (near the max for early July) will certainly allow for widespread showers with drenching downpours setting up later Monday night through at least part of Tuesday, before another round of showers and maybe a better chance of thunderstorms arrive later Tuesday into Tuesday night. There are some signals that heaviest rain on Tuesday night may remain just to our south, but probably too early for those type of details. If both rounds of moderate to heavy rain impact similar areas, could have additional impacts in terms of flooding. WPC continues to highlight majority of our area within slight risk for excessive rainfall. At this point, does appear greatest risk for severe storms may remain to our west late Tuesday into Tuesday night with MUCAPES are well over 1000J/kg. If sufficient instability makes it into central WI, could be stronger storms with more than sufficient effective shear progged. Looking ahead for the period around the holiday, the day before the 4th looks dry and seasonably warm with highs in the 80s. Unfortunately, the active pattern does not look to take a holiday and more rain is expected to move back in later on the 4th and lasting into Friday. Some timing differences in models, especially in how quick shower chances return for Thursday afternoon and Thursday evening. Unsettled weather pattern continues into the weekend as slow moving low pressure system only slowly exits to the east. Given that, temperatures will likely be at or even slightly below normal. && .AVIATION...for 00Z TAF Issuance Issued at 632 PM CDT Sat Jun 29 2024 Post-frontal low clouds and a few light showers will impact the region this evening, with widespread MVFR ceilings occurring over north central WI. Clearing will commence late this evening into the early overnight hours, followed by VFR conditions for the rest of the TAF period. Strong northwest winds will continue this evening, then subside overnight. Winds will veer NE-E near lake Michigan Sunday afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....JLA AVIATION.......Kieckbusch