Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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090 FXUS63 KGRB 180915 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 415 AM CDT Tue Jun 18 2024 Forecast discussion for routine morning forecast issuance .KEY MESSAGES... - Hot and humid weather is expected today, with heat indices in the low to mid 90s in most places. A few places in the Fox Valley and west of the bay could have heat indices in the upper 90s. It will be considerably cooler near the Lake Michigan shore. - Gusty south winds could create large waves and strong currents at Lake Michigan beaches this afternoon and tonight. A Beach Hazard Statement has been issued. - The gusty south winds will also create conditions hazardous to small craft on the lake and bay today and tonight. - Thunderstorms are likely in central and northcentral Wisconsin tonight, and in eastern Wisconsin Wednesday. Some storms could produce strong winds and torrential rains. && .DISCUSSION... Issued at 413 AM CDT Tue Jun 18 2024 Short Term...Today...Tonight...and Wednesday The surface warm front was approaching the Michigan border at 09z. Wisconsin will be in the warm sector of the surface low lifting north across the Plains states today. The models really do not show any significant upper air or surface feature to trigger thunderstorms today, though there is plenty of warmth and moisture in the atmosphere. There could be isolated storms this afternoon, perhaps along a lake breeze, but left them out due to low probability. Hot and humid weather is expected today, except near the lakeshore. Heat indices will be mostly in the low to mid 90s away from the lake, with a few places in the Fox Valley and west of the bay reaching the upper 90s. It will be much cooler near the Lake Michigan shore, with highs in the lower 70s but with a gusty wind. Thunderstorms will move into central and northcentral Wisconsin tonight as the cold front moves into northwest Wisconsin. A few storms with strong winds and torrential rain are possible. High dewpoints and clouds will make for a very mild night, with lows in the 70s in most places. Thunderstorms will arrive in eastern Wisconsin Wednesday as the cold front moves slow across the state. Highs will range from the middle 70s in northcentral Wisconsin to the low 80s in the Fox Valley. Long Term...Wednesday Night Through Monday An unsettled pattern is forecast to persist through much of the extended period with low to middle end PoPs (30-70%) progged for each day through Sunday. With the chance for successive rounds of showers and storms and anomalously high available moisture, minor flooding as well as rising levels on area rivers and streams looks to be the main impact through the extended period. Wednesday night through Sunday...A few showers and thunderstorms may linger across east-central WI into Wednesday night as a cold front departs the region. Expect mostly dry conditions across the rest of the region overnight into Thursday morning as cold air advection behind the front brings an area of widespread subsidence. This dry spell looks to be rather short lived as models show return flow bringing a surge of warm moist advection into the upper-Midwest. An upper-level right rear jet quad is progged to provided additional synoptic scale ascent during this period. The severe weather potential during this period looks rather low given weak instability and the lack of a more robust forcing mechanism. A developing low-level jet overnight Thursday into Friday morning may be able to sustain some isolated to scattered showers, but with nocturnal stabilization this may be another period during which the region could see a lull in the precipitation. The chances for widespread rain with embedded thunderstorms then increase Friday with another surge of warm moist air out ahead of a developing low pressure system. With PWATs forecast to approach 1.75-2 inches (near 99th percentile of climatology) periods of heavy rain fall will be possible, particularly along warm front which is forecast to set up across northern WI. The severe weather potential does increase Friday afternoon and evening compared to Thursday, especially across central WI where SBCAPE are forecast to reach 1000-1500 J/kg and effect shear values range from 25-30 kts. However, with widespread cloud cover expected and a lack of a clear cut forcing mechanism there are pitfalls that may hinder storm development during this period. As the axis of anomalously high available moisture and low pressure system continue to propagate across the region through Saturday periods of heavy rain are expected to continue. The best chance for severe weather during the extended period may come Saturday afternoon and evening as the attendant cold front sweeps across the region. There is a high level of uncertainly with the severe potential during this period, but currently long range guidance is showing upwards of 2000 J/kg MUCAPE and effect shear of 20-30 kts which could support some stronger to severe storms. Behind the cold front perception should become more scattered with areas of showers lingering into Sunday as the region remains in the cyclonic flow, but the threat to any severe weather Sunday looks minimal at this time. In terms of the flooding potential, long range ensembles are forecasting about 2-2.5 inches of QPF from Wednesday night through Sunday across the region. Locally higher amounts may be possible if heavier rainfall hits the same area multiple times. WPC has introduced a slight risk (15%) for excessive rainfall across northern WI and a marginal risk (5%) across central and east-central WI both Friday and Saturday. Rest of the extended...Long range ensembles are in decent agreement with a broad low amplitude ridging moving over the region Monday. Expect this ridge to bring a more prolonged period of dry and seasonal weather to start next week. Temperatures...While temperatures may trend a few degrees above normal each day during the extended there is only a minor risk of heat related impacts. && .AVIATION...for 06Z TAF Issuance Issued at 1152 PM CDT Mon Jun 17 2024 VFR conditions prevailed across the area late this evening, as the evening showers/storms exited/weakened. Mainly VFR conditions are expected tonight, with some lower MVFR ceilings impacting northern WI (RHI) during the early overnight hours. A brief shower or storm will remain possible overnight as well, locally lowering flying conditions. A broken line of showers and storms will approach from the west after 00z Wednesday, likely reaching the Fox Valley and lake shore after 06z Wednesday. Instability will be waning, so thunder chances will also be decreasing through the evening hours. Will not include any thunder mention this far out. Surface winds will remain under ~10 kts overnight, with LLWS expected as winds at 2000 ft increase to around 30kts. It will be a hot and humid Tuesday, with VFR conditions expected most of the day. Breezy south winds are expected, gusting to 30 kts. A few higher gusts are possible during peak mixing. Another period of low-end LLWS is expected Tuesday evening if/where surface winds stop gusting. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement from 10 AM CDT this morning through Wednesday morning for WIZ022-040-050. && $$ DISCUSSION.....RDM/GK AVIATION.......Bersch