Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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825 FXUS63 KGRB 161811 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 111 PM CDT Sun Jun 16 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Showers and scattered thunderstorms are expected to exit northeast Wisconsin late this morning or early this afternoon. Heavy rainfall is likely, especially north and west of the Fox Valley. High rainfall rates may result in localized urban flooding and ponding on roads. - Another round of thunderstorms is possible tonight. A few storms may become severe, especially over north central Wisconsin. Large hail, gusty winds and heavy rainfall will be the main threats. - Well above average temperatures are expected Sunday through Tuesday. Heat indices may reach the lower to middle 90s at times Monday and Tuesday across central, east central and portions of northeast Wisconsin. - Periodic thunderstorm chances are possible through mid-week. Some strong storms and locally heavy rainfall may be possible at times. && .DISCUSSION... Issued at 407 AM CDT Sun Jun 16 2024 Short Term...Today...Tonight...and Monday Several clusters of showers and storms were ongoing across WI, eastern MN and NE IA early this morning, but coverage varied considerably. These areas of convection were being driven by a combination of WAA with a 45-55 kt low-level jet, and a couple MCVs; one over NW WI and another in NE IA. Elevated instability was edging into the western part of the forecast area, where a narrow band of storms was developing. PWATs had increased to 1.5 to 1.75 inches over western WI. At the surface, a warm front extended from southern MN into SW WI. Overall, the timing of today`s short-waves/MCVs is a bit slower than was depicted the past few days. Have slowed down the departure of the precipitation by a few hours, which will likely delay the northward push of the warm front. Consequently, have lowered max temps by several degrees and kept extensive cloud cover around longer into the afternoon. Not expecting much additional precipitation after the initial surge shifts northeast of the region, but kept slight chance pops in northern WI, where the warm front will likely reside later this afternoon. High temperatures should range from the middle to upper 70s north to the middle 80s south. Tonight, a cold front is expected to edge into NC WI later this evening and overnight. While models offer myriad possible scenarios for convective development, suspect most of the activity will occur near this boundary, so will keep the highest pops over NC WI. With fairly strong elevated instability in place and 30-40 knots of deep layer shear, a few strong to severe storms could develop and produce large hail, gusty winds and heavy rainfall. A short-wave trough is expected to approach NC WI late tonight, and move through the Northwoods Monday morning. Have increased pops to likely with this feature. The front will stall out over northern WI on Monday, with resurgent southerly flow resulting in overrunning during the afternoon. This should keep the highest pops centered over northern WI. Farther south, partial clearing could allow temperatures to surge into the upper 80s to lower 90s, with heat indices reaching the lower to middle 90s. Long Term...Monday Night Through Saturday An active pattern is shaping up next week as the 500mb ridge across the eastern United States flattens by the end of the upcoming work week. This will result in periodic chances for thunderstorms through the entire work week, heat and humidity on Monday and Tuesday with temperatures returns closer to normal Thursday and Friday. For Monday night, the close proximity to the warm front is enough to keep the chances of thunderstorms during the evening across the north. Although the forecast is dry overnight, the front is relatively close and am concerned some convection will make it into there. Will pass my concerns on to the day shift. For Tuesday, the day should start out warm and humid as well as dry. Daytime-heating with highs in the middle 80s to lower 90s are expected. Bufkit soundings do show the cap weakening during the afternoon, enough to support the chances of storms. Bufkit soundings indicated around 2,000 J/Kg of CAPE with dry air in the mid levels of the atmosphere. 0-6 km shear values are only around 20 knots, so pulse type storms are expected. The strongest storms could produce wet microbursts/damaging wind gusts and hail. For Tuesday night, showers and thunderstorms across Minnesota may move east into the area. Stronger storms are possible. On Wednesday, the cold front will finally slide to the east into and across the area. It may still get hot as some models are slower the frontal passage. A lot of uncertainty in the potential for severe thunderstorms due to the frontal position, cloud cover and ongoing showers and storms Wednesday morning. Beyond Wednesday, the ECMWF has the frontal boundary meandering across the northern United States, resulting in additional chances of storms. It is too early determine if any of these storms would become severe. Temperatures by the end of the work week should return closer to normal. && .AVIATION...for 18Z TAF Issuance Issued at 110 PM CDT Sun Jun 16 2024 Lingering showers over far eastern WI early this afternoon will continue to exit in the next couple hours. While VFR conditions will prevail in its wake across the east-central WI TAF sites through late this evening, MVFR cigs will prevail at the central and north-central WI TAF sites. Some clearing is also expected at times across the central and east-central WI TAF sites through this evening. A cold front is forecast to drop southeast into north-central WI sometime this evening and continue sagging southeast through the night. Low cigs/vsbys, showers, and thunderstorms are anticipated to accompany the front. However, guidance is struggling to agree on the timing of the frontal passage. Based on current guidance and trends, have the showers and storms moving through the RHI TAF site between 02z and 06z, central WI TAF sites around 03z to 06z, and the east-central WI TAF sites around 06z to 09z. Confidence in timing decreases as the front moves further southeast through the night. Additional showers and thunderstorms are possible on Monday, but will depend on where the cold front will stall out over the area. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement through late tonight for WIZ022-040-050. && $$ DISCUSSION.....Kieckbusch/Eckberg AVIATION.......Kruk