Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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448 FXUS63 KGRB 240345 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1045 PM CDT Mon Sep 23 2024 Updated aviation portion for 06Z TAF issuance .KEY MESSAGES... - Patchy frost and fog is possible across north central Wisconsin late tonight. - Near normal high temperatures are expected on Tuesday before returning to above normal values midweek through next Monday. High temperatures could run as much as 10 to 15 degrees above normal. && .DISCUSSION... Issued at 335 PM CDT Mon Sep 23 2024 Short Term...Tonight and Tuesday Main forecast concerns in the short-term are cloud/precip trends and the potential for frost and fog development overnight. This afternoon`s satellite imagery showed lake-effect clouds in far eastern WI, with clearing skies further west across the rest of the forecast area. Meanwhile, high clouds were just starting to lift into east-central WI from shortwave energy to the south. This evening and tonight...The weak mid-level shortwave will gradually lift into the area and phase with a trailing mid-level trough during this time period. There are some signals for isolated showers or sprinkles to lift into east-central WI late tonight into Tuesday, but forecast soundings indicate there may be too much dry air in the low to mid-levels. Decided to only include very small chances for showers and sprinkles. Otherwise, anticipate middle and high clouds to spread over the entire forecast area with dry conditions prevailing for the majority of the time. Despite another night of cooler temperatures (lows in the middle 30s to low 50s), the coverage of middle and high clouds in north-central WI, where temps will be coldest, should hinder frost development. However, there will still be a decent low-level temperature inversion and light winds, which may allow for patchy frost and fog to develop in some spots across northern WI. Tuesday...With the mid-level trough overhead, anticipate similar conditions to continue into Tuesday with a small chance for showers or sprinkles in east-central WI and dry conditions elsewhere. However, some clearing will occur across the western part of the forecast area, while an onshore wind will help keep clouds over far eastern WI. High temperatures will be similar to today (near normal) with values ranging from the middle 60s to low 70s. Long Term...Tuesday Night Through Monday Normal highs start out this week in the upper 60s but by next Monday are in the low to mid 60s. Good to recalibrate in terms of temps as after a couple day hiatus, high temps will surge much above normal again. A few locations will likely reach the 80 degree mark Thu-Sat. Rain chances the rest of the workweek will be minimal. Outside chance that an isolated light shower occurs early Tuesday evening near the lakeshore (mainly Door County) as shortwave trough exits across the central Great Lakes. Next chances for rain will not occur until the weekend. However, these chances will be highly dependent on fate of what will eventually become tropical system Helene within the next couple days over the northwest Caribbean Sea. There is good agreement that the system tracks north- northeast and will make landfall across the eastern Gulf Coast states by Friday. The remnants of the tropical system will then dumbbell (aka Fujiwara) around the closed low present over Arkansas late this week. Unsure how far north the system will be propelled, but that potential along with deeper moisture advecting into the western Great Lakes due to the system does result in some models generating some showers with minimal thunder. Canadian is most aggressive at this point compared to other primary extended models and ensembles (ECMWF and GFS). Only minor change was to delay pops on Friday night and slow the northward progress of pops on Saturday. The low chances of rain persist Sunday and Monday. Deep moisture lingers with an approaching trough from the northern plains. Ensembles are showing a consistent signal for at least small chances for QPF, so thought best to leave those two days alone at this point. Even with the potential for some rain, high temps still look to be at least in the lower 70s. && .AVIATION...for 06Z TAF Issuance Issued at 1033 PM CDT Mon Sep 23 2024 Mid and high clouds will continue to spread into the region during the overnight hours. There is still potential for patchy fog to develop by early Tuesday morning in central and north-central WI, but the cloud cover may hinder this fog development. Additionally, there is potential for a slight chance of a shower or sprinkle across central and east-central WI late tonight into early Tuesday morning. With confidence not very high in where the showers may occur, have opted to keep the TAF sites dry. High pressure should then clear out the clouds Tuesday afternoon, with mostly clear skies expected into Tuesday night. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kruk/JLA AVIATION.......Kurimski