Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI
Issued by NWS Milwaukee/Sullivan, WI
981 FXUS63 KMKX 240922 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 422 AM CDT Sun Aug 24 2025 .KEY MESSAGES... - Much cooler, less humid, and breezy into early next week. - Widely scattered rain showers expected in the region this afternoon, dwindling into the evening. - Some waterspouts are possible across Lake Michigan through Monday. Late this morning through this evening appears to be the primary window of concern. && .SHORT TERM... Issued 422 AM CDT Sun Aug 24 2025 Today and Tonight: Mostly clear skies this morning with colder air moving in across the state. Current temps this morning are in the lower to upper 50s. Weather will remain dry through the morning as much colder around 850 mb begins moves in. As the colder air moves in aloft, widely scattered to isolated rain showers are expected to develop across the state and Lake Michigan. The best potential for showers to develop will be this afternoon and evening with POPs around 15 to 35%. East central through northeastern Wisconsin will have the best potential for rain overall as the best lift and mid to upper level support will be found there. For lakeshore areas and Lake Michigan some of these showers will be able to tap in lake-effective convective instability (colder air over warmer water). This could produce a few thunderstorms and waterspouts over the nearshore and open waters (discussed further in the Marine section of the AFD). With the prevailing wind direction coming from the northwest and a lack of instability over land, there are no concerns for any waterspout like activity over the state. Can`t rule out a stray rumble of thunder or two, but even this is pretty unlikely given the subsidence seen in forecast soundings. Dry weather will return again later this evening into the overnight hours with mostly clear skies. Once we loose diurnal heating, what little instability/lift we have will diminish and end. Brisk winds are still anticipated Monday afternoon into Monday evening as the low pressure system near James Bay continues to deepen. However, high pressure to the northwest will begin to move in late Monday. Patterson && .LONG TERM... Issued 422 AM CDT Sun Aug 24 2025 Monday night through Saturday: One more amplified 500 mb shortwave trough should slide southward across the region Monday night into Tuesday, shifting to the southeast Tuesday night. This should continue to bring at least scattered stratocumulus clouds to the area, with weakening winds as high pressure moves southeast closer to the area. Below normal temperatures will continue during this time, with lows in the middle to upper 40s Monday night and Tuesday night, and highs only in the upper 60s to around 70 Tuesday. These temperatures are supported by the NBM and ensembles with small spread in possible temperature ranges. Northwest flow at 500 mb is then anticipated for the rest of next week, with a weak ridge possibly approaching for Saturday. Temperatures should slowly moderate more toward seasonal normal values, as high pressure moves off to the southeast. There may be small chances for showers later in the week, though this far out a lot of uncertainty exists with any shortwave troughs moving through the region and the upper air trends. Kept the forecast dry for now given this uncertainty. Wood && .AVIATION... Issued 422 AM CDT Sun Aug 24 2025 Mostly clear skies early this morning will again give way to to more scattered to broken stratocumulus clouds around 4 to 6 kft. Stratocumulus clouds will begin developing again mid morning through this evening. This scattered to broken cloud deck should dissipate again after sunset. There could be a few isolated showers with these clouds, but coverage and chances are low. The best potential will be for terminals across northern and central Wisconsin included SBM. Northwest winds will pick back up again by mid morning with brisk winds and gusts near 20 knots expected. Winds will again diminish tonight after the sun sets. Patterson && .MARINE... Issued 422 AM CDT Sun Aug 24 2025 Low pressure over James Bay will continue to deepen today through Monday, which will keep the brisk northwest winds persistent through this period. Therefore the borderline Small Craft Conditions remain. As daytime mixing increases in the afternoon/evening gusts will range from 20 to 25 kts with any gusts at or above Small Craft Criteria being few and far between. This will be identical to the conditions we saw yesterday across the nearshore and open waters. Winds are off shore so there is no concern for any building waves. Winds will remain brisk through Monday evening and then diminish heading into Tuesday as high pressure moves in from the northwest. The other big thing to keep an eye on will be the potential for waterspouts. There will be scattered to isolated rain and thunderstorms developing this afternoon and evening. Any Convective Cloud Depth that is around 6 to 7 kft will have the potential for waterspout development. Were is a good synoptic set up with the low over James Bay and the delta T`s over the lake will be more than sufficient for waterspout development. The northern half of the lake will have the best potential for waterspouts as they have the better Convective Cloud Depth and delta T`s. As the colder air continues to expand southward down the lake, the waterspout potential will expand. Patterson && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, X, and YouTube at: www.facebook.com/NWSMilwaukee www.x.com/NWSMilwaukee www.youtube.com/NWSMilwaukee