Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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541 FXUS63 KGRB 240906 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 406 AM CDT Mon Jun 24 2024 Forecast discussion for routine morning forecast issuance .KEY MESSAGES... - A severe thunderstorm complex could produce damaging winds as it moves from northwest Wisconsin this evening to Lake Winnebago late tonight. - Conditions hazardous to small craft are possible late tonight and Tuesday morning along Lake Michigan. - Some rivers and streams will remain above bankfull into the middle of the week. && .DISCUSSION... Issued at 405 AM CDT Mon Jun 24 2024 Short Term...Today...Tonight...and Tuesday Patchy ground fog should dissipate shortly after sunrise. Mostly sunny skies and warm temperatures are expected today, with increasing high clouds during the day. A shortwave trough moving across Wisconsin will create upper diffluent flow, while a strong jet at 850mb brings up warmth and moisture. The combination of these should produce a thunderstorm complex that could move from northwest WIsconsin this evening to Lake Winnebago shortly after midnight. This would produce a path of damaging winds if it does materialize. If an organized complex does not occur, there will still be a broken line of storms that could produce large hail and damaging winds. The activity should exit the forecast area by daybreak Tuesday, with clearing skies and warm temperatures by afternoon. West winds downsloping across eastern Wisconsin should produce temperatures in the middle to upper 80s, even at the bay and Lake Michigan beaches. Long Term...Tuesday Night Through Sunday Primary period of focus for the extend forecast is Friday into Saturday morning as a slug of gulf moisture surges into the region ahead of an approaching low. Otherwise, mostly dry and cooler temperatures are forecast for the middle of this week. Tuesday night through Thursday...With an upper-level short-wave departing the region and a ridge of high pressure building in behind dry conditions are expected for the middle of this week. Northerly winds Wednesday will usher in seasonally cool temperatures with highs on Wednesday forecast to reach the middle 60s to low 70s, and overnight lows into Thursday dropping into the middle 40s to low 50s. Friday through Saturday...Ensembles are in general agreement that rain will return to the region Friday as an area of isentropic ascent over spreads the region. Periods of moderate to heavy rain do look possible as forecast sounding show deep layer saturation and PWAT values reaching 1.75-2.00 inches which is around the 90th percentile of climatology. Probabilistic guidance has a 35- 50% chance for greater than 0.5 inches of rain during this period. With several area rivers expected to still be at or near bankfull there are some minor flooding concerns. The potential for stronger thunderstorms during this period is still unclear. Models are showing increasing instability Friday night into Saturday morning ahead of a trailing cold front which could initiate scattered thunderstorms, but it`s unclear if these storms will develop in an environment capable of producing severe hazards. Rest of the extended...Another cool start to the day Sunday with early morning lows in the middle 40 to middle 50s as winds become northerly. A building ridge should keep the remainder of the weekend and the start of next week dry. There are some signs anther system will traverse the northern CONUS during the middle of next week which would keep the wet start to summer going into July. && .AVIATION...for 06Z TAF Issuance Issued at 1050 PM CDT Sun Jun 23 2024 Dry conditions are expected overnight. Continue to monitor fog trends as some models want to bring in some lower ceilings/visibilities, but SREF/HREF continue to show low probabilities (under 30%) of under 3SM, so will just keep some MVFR/IFR conditions in TEMPO groups. Ground fog may produce locally lower visibilities as winds go variable overnight. VFR conditions are expected on Monday with some fair weather cumulus clouds expected, with some mid-high clouds spreading in later in the day. A complex/line of showers and storms is forecast to race across the region Monday evening/night, likely after 03-06z Tuesday, but still some uncertainty as to where it will track and how intense/widespread it will be. Have include a TEMPO group at the end of the TAF period for AUW/CWA/RHI. Some wind shear will also be possible Monday evening as winds aloft increase to 35+ kts. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....RDM/GK AVIATION.......Bersch