Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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680 FXUS63 KGRB 191113 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 613 AM CDT Wed Jun 19 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Quite a bit cooler today than yesterday, along with a chance of showers and thunderstorms. -An active pattern is expected to continue through the end of this week and into this weekend. Stronger storms and locally rainfall will be possible each day, with the greatest risk for excessive rainfall coming Friday and Saturday. && .DISCUSSION... Issued at 413 AM CDT Wed Jun 19 2024 Short Term...Today...Tonight...and Thursday A cold front will move across the region today and bring scattered showers and thunderstorms, especially across east central Wisconsin. Gusty winds and brief heavy rain are possible, but severe storms are not expected. Highs today will be around 5 degrees above normal, but about 15 degrees cooler then yesterday. The front will stall across the southeast part of the state during the evening hours, which may keep scattered showers going across east central Wisconsin. Lows tonight will be close to normal. An upper trough will move across the area Thursday, and produce scattered showers and isolated thunderstorms. Showers, clouds, and northeast winds from Lake Michigan will make for a cooler than normal day, especially south of highway 29. Long Term...Thursday Night Through Tuesday A low pressure system developing over the central Plains and ejecting toward the western Great Lakes Friday and Saturday will be the dominate feature of the extended period. With abundant moisture forecast to be available during this time expect a few rounds of heavy rainfall that may cause area rivers and streams to rise near or to bankfull. Thursday night through Sunday...A weak high pressure system developing over Lake Superior Thursday night into Friday morning may bring a brief lull in the precipitation. Chance for showers and thunderstorms will then ramp up Friday afternoon as a surge of warm moist air lifts over the region ahead of a low pressure system developing in the Central Plains. PWATs are progged to range from 1.75 to 2 inches Friday afternoon which is around the 97th percentile for this time of year. The combination of widespread lift and robust available moisture makes periods of heavier rain possilbe Friday afternoon and evening. The potential for severe weather is low as instability looks rather weak (less than 500 J/kg) and forecast soundings do show a cap over much of the region Friday afternoon and evening. The chance for thunderstorms and heavy rain will continue through Saturday as the main surface low phases with an upper level shortwave propagating east along the US/Canada boarder. Forecast soundings Saturday afternoon show PWATs approaching 2-2.25 inches which is the 99th percentile of climatology. With the strong PV anomaly associated with the low and robust moisture expect periods of heavy rain through the day Saturday. The severe weather potential has trended downward over the last 24 hour hours as models now show the warm front stalling out over souther WI and shunting the stronger instability south of the region. However, won`t rule out some strong thunderstorms late Saturday as a cold front sweeps across the region. Showers and weak storms may linger through Sunday as the area remains in the cyclonic flow. In terms of the flooding concern for Friday and Saturday, much of the region is in a slight (15% chance) risk for excessive rainfall both days. Probabilistic guidance is showing about a 15- 30 percent chance for greater than 2 inched of rain over the two days, highest in central and north- central WI. Rest of the extended...A developing ridge of high pressure Monday should bring a reprieve from the showers and storms to start next week. However, does not look like this dry stretch will last long as ensemble models show the upper-level pattern flattening out toward the middle of next week with signs that the round of thunderstorms may sweep through the region next Tuesday and Wednesday. Temperatures...With the chances for rain and widespread cloud cover temperatures should trend slightly cooler than the beginning of this week, however, the humidity will stick around until the cold front comes through Saturday. Does look like heat and humidity will return during the early to middle part of next week. && .AVIATION...for 12Z TAF Issuance Issued at 613 AM CDT Wed Jun 19 2024 A period of MVFR ceilings is likely this morning as a cold front moves across the region. It will also be accompanied by scattered showers and isolated thunderstorms. Scattered showers and isolated thunderstorms are possible in the afternoon east of a MNM to DLL line, with VFR conditions expected otherwise. An upper level disturbance will bring additional showers late tonight and Thursday with MVFR conditions south of a SUE to AUW line. Low clouds are expected along the Lake Michigan shore, with IFR conditions possible at MTW and SUE. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement until 10 AM CDT this morning for WIZ022- 040-050. && $$ DISCUSSION.....RDM/GK AVIATION.......RDM