Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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759 FXUS63 KGRB 212106 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 406 PM CDT Sat Sep 21 2024 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - There is a marginal risk of severe storms with quarter-sized hail and strong winds across central and north-central WI into early this evening. - A period of gusty north winds and building waves Sunday into Monday morning will likely bring a period of hazardous conditions to small craft on Green Bay and Lake Michigan. - Temperatures will return closer to normal from Sunday through the middle of next week before trending above normal again late next week. && .DISCUSSION... Issued at 405 PM CDT Sat Sep 21 2024 Short Term...Tonight and Sunday Precipitation trends are the main focus from this forecast period. This afternoon`s radar imagery showed scattered showers and isolated elevated thunderstorms across the region. The thunderstorms were mainly focused in central WI where the better elevated instability and WAA prevailed. As a result, the storms struggled to stay intact with an eastward progression and became scattered showers as they reached east-central WI. Further west, isolated thunderstorms continued to develop in the pool of instability and ahead of/along an approaching cold front. The evolution of these storms through this evening will be the main forecast challenge. Precipitation...Model guidance was struggling to latch onto the current situation throughout the day, which has led to a forecast mainly based on radar/satellite trends and mesoanalysis/surface observations. That being said, until the cold front moves closer to the forecast area, anticipate isolated thunderstorms to continue developing in central WI and weakening to showers as they move eastward through late this afternoon. Given the large pool of instability, there will still be a threat for hail with some of the stronger storms through this afternoon. Models indicate additional showers and storms to develop ahead of the cold front into this evening as the instability pool slowly moves eastward into central WI. Therefore, anticipate a threat for hail and gusty winds with any of the stronger storms associated with the front this evening. The The stronger storm threat will wane as the night goes on due to a loss in instability, but non-severe thunderstorms will still be possible through Sunday morning. The precip chances will continue in far eastern WI through Sunday afternoon until the front completely exits the forecast area in the evening. Temperatures...Today was the last day of above normal temperatures with many locations in eastern WI reaching the 80s. However, clouds and precip prevented temperatures in central and north-central WI to rise into the 80s. The cold front will bring much cooler temperatures to the region with highs only climbing into the 60s. Long Term...Sunday Night Through Saturday Cold front that shifts across the area late this weekend will carry any chances for showers out of northeast WI on Sunday evening. Skies will clear from north to south the rest of the night and with PWATs crashing down and winds becoming light, temps could tank across northern WI. Lowered temps a bit in the north leading to mins into the mid to upper 30s. Could be some fog with patchy frost over far northern WI near the Upper Michigan border. Monday will be dry as ridging aloft and at the sfc prevails. Another cool night is expected Monday night over the far north with fog and frost again possible. The only blemish on a mostly dry week then arrives late Monday night and Tuesday as upper low over the southwest CONUS this weekend works its way east-northeast. Though it appears bulk of showers with this feature remain over the central Great Lakes, there could be a few showers into east-central WI on Tuesday (20-30% chances). Rest of the week does look dry though as troughing re-asserts itself farther east over the lower Great Lakes while ridging with 590+ dam heights builds over the western Great Lakes. After a brief cooldown, daytime temps will rebound back above normal as early as Wednesday with highs in the middle 70s through rest of the week. Does not look like we`ll see much in the way of 80s though. Nighttime temps will also gradually warm, with readings in the 40s to lower 50s by late this week. Very low chances (mainly less than 20%) for rain return by next weekend, though indications are that sprawling high pressure at the sfc tied to the ridging aloft will continue to keep conditions dry. && .AVIATION...for 18Z TAF Issuance Issued at 125 PM CDT Sat Sep 21 2024 VFR conditions prevailed across the area early this afternoon, as high clouds spread from the west from thunderstorms in western/west-central WI. Given all guidance does not have this area of showers and thunderstorms at this time, based the early hours of the TAFs on satellite and radar trends. Therefore, confidence is not high for the evolution of these showers and storms into this afternoon. Based on trends, anticipate the central WI TAF sites to see the best chance for thunderstorms this afternoon, with a lower chance at the RHI TAF site. These storms will struggle to move eastward this afternoon due to a lack in instability. However, anticipate these storms to remain with VFR cigs. Another chance for thunderstorms, with MVFR cigs, will move across the area from northwest to southeast, in association with a cold front, mainly between 00z and 06z Sunday. A few of these storms may be strong and produce hail and gusty winds, especially at the central and north-central WI TAF sites. Additional showers are possible in east-central WI Sunday morning. Decided to include ceilings lowering after midnight as models continue to show this solution. Winds will turn north after midnight into Sunday morning following the cold front. Gusts up to 20 kts will be possible for Sunday morning. && .MARINE... Issued at 405 PM CDT Sat Sep 21 2024 A period of hazardous conditions for small craft looks to develop on Sunday as gusty north winds develop behind a cold front. Could have a brief period of stronger winds close to/behind the front as the initial surge of cold air advection arrives late tonight, then a little lull during the day on Sunday, with stronger winds arriving aloft later Sunday afternoon which should mix down. Gusts to 25-30 kts are expected with waves generally building to 2-5 ft, highest waves south of Sturgeon Bay. Winds and waves will slowly decrease Monday morning. && .CLIMATE... Issued at 405 PM CDT Sat Sep 21 2024 The record stretch of consecutive days in the 80s during September continues. High temperatures have already reached the lower 80s today at Green Bay, so one more day will be added to the record. There is still a chance Wausau will see highs reach 80 later this afternoon. The streak will end after today as much cooler air works into the region tonight and Sunday. At Green Bay, the high today has already cracked the lower 80s, marking the 11th consecutive day in the 80s. The old September record of consecutive days in the 80s was 9 days set from Sep 16-24, 1891 and from Sep 1-9, 1933. At Wausau, the high Friday was 80 degrees, marking the 10th consecutive day in the 80s. The temperature today could still reach 80 which would mark the 11th straight day of 80, but that is not a sure thing. The old September record of consecutive days in the 80s was 8 days set from September 4-11, 1978 and from September 17-24, 1908. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kruk/JLA AVIATION.......Kruk MARINE.........Kruk CLIMATE........JLA