Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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639 FXUS63 KGRB 091831 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 131 PM CDT Sun Jun 9 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Isolated sprinkles/showers across the north today. Next chance for storms arrives Tuesday PM with additional chances late in the week. - Chilly tonight with the potential for patchy/areas of frost over north-central Wisconsin. - Below normal temperatures today through Tuesday with a warm-up expected mid to late week. && .DISCUSSION... Issued at 405 AM CDT Sun Jun 9 2024 Fairly quiet conditions expected to start the week, then things turn more active mid-late week as a parade of shortwaves will bring periodic shower/storm chances to the region. Main forecast concerns will be determining how widespread the sprinkles/showers will get today, how cold it gets tonight, how warm it will be later this week and timing/strength of the mid-late week systems. Shower/Storm Chances & Clouds/Winds: A dry start to the day is expected with sunshine for much of the area. But clouds will be invading from the north through the morning as an upper jet drops south of the region, a shortwave will rotate south across the state through the day. This, along with colder air aloft and weak lift in the mid-levels, should generate a few sprinkles or showers, mainly over northern WI. Some of the sprinkles could sneak further south than models depict. Models do not generate any measurable precip today, but would not be surprised if we can squeeze out a hundredth or two somewhere over the north. No thunder is expected as instability will be near zero. Northwest winds will be a little on the breezy side later this morning and afternoon, with gusts of 20 to 30 mph. Look for skies to clear from north to south late this afternoon and early evening. Next chance for showers arrives Tuesday afternoon and evening ahead of a quick moving shortwave and front. Forcing and moisture look pretty narrow/brief, so not expecting a long period of showers or significant rain totals. Instability looks very marginal, likely under 300-400 J/kg. So a few storms will be possible, but no severe storms are expected. Fast, zonal flow over the northern CONUS will allow the next shortwave and frontal boundary to arrive later on Wednesday. Models hinting at a complex of storms forming somewhere west of the area and spreading E/SE through the region. But due to timing and strength differences, it will remain difficult to pin down any details on how things will play out. With building instability and shear, severe weather concerns will need to be monitored. As the upper flow turns to the southwest late in the week and next weekend, additional chances for showers and storms look to arrive, but quite a bit of uncertainty exists as to when the better chances arrive as a lot has to play out ahead of this system. Temps / Frost Potential: An impressive push of CAA arrives today, with 850mb temps dropping to between 3-7C, resulting in below normal temps. This supports highs ranging from around 60 in far north-central WI to the lower 70s in the south. If clouds are a little slower to clear, temps will likely not make it out of the 50s over the north. As skies clear and winds diminish tonight, temps will fall into the 30s and 40s. Where winds go calm over north-central WI, some areas/patchy frost is likely. MET MOS guidance still showing a low of 32F at Land o Lakes, which is likely a good indication of how low temps could fall. A Frost Advisory may be needed for far north-central WI. Near to slightly below normal temps are expected Monday and Tuesday, then look to climb back above normal on Wednesday and Thursday. Still some question to just how much we warm up at the end of the week as any complex of storms could keep more clouds in the region, along with keeping the front further south. && .AVIATION...for 18Z TAF Issuance Issued at 131 PM CDT Sun Jun 9 2024 A layer of overcast cloud cover will move across the region this afternoon and evening. This will bring some MVFR ceilings across northern WI but may also briefly bring some MVFR ceilings to portions of central to east-central WI. The clouds will move off again in the early overnight period, bringing back good flying conditions and VFR skies for the remainder of the period. Northwest winds remain gusty through this afternoon as well, but will become lighter overnight. && .MARINE... Issued at 405 AM CDT Sun Jun 9 2024 Another marginal set up for conditions hazardous to small craft today as north to northwest could gust to around 25 kts. Stronger winds aloft early this morning, but stability issues will likely hamper the winds making it to the surface. This afternoon, better mixing is expected, especially near the shore, but winds aloft come down a little. Colder air will aid in better mixing through the day, with water temps in the 50s on Lake Michigan and 50s to low 60s on the bay. Waves will stay under criteria, but it will be quite choppy with waves of 1-4 ft. Leaned on the cautious side and issued a Small Craft Advisory for this afternoon/early evening. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Bersch AVIATION.......Uhlmann MARINE.........Bersch