Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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459 FXUS63 KGRB 241133 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 633 AM CDT Tue Sep 24 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Small precipitation chances over mainly eastern WI today into early tonight, then dry until the remnants of the developing hurricane in the Gulf of Mexico approach this weekend. - Near normal high temperatures are expected today before returning to above normal midweek through next Monday. High temperatures could run as much as 10 to 15 degrees above normal. && .DISCUSSION... Issued at 341 AM CDT Tue Sep 24 2024 Short Term...Today...Tonight...and Wednesday Forecast concerns include small precipitation chances through this evening, fog potential and temperatures. WV imagery showed an upper trough axis near the Dakotas/MN border early this morning, with a short-wave lifting north through WI. At the surface, a weak inverted trough was noted over eastern WI. Radar showed isolated to scattered showers across the region, though abundant dry air in the 850-700 mb layer was preventing much of this from reaching the ground. Additional showers associated with a weakening cold front over MN were eroding as they approached WI. Patchy fog was observed in parts of NC WI, where there were some breaks in the clouds. The short-wave will lift north this morning, and the inverted surface trough is expected to gradually weaken during the day. Will carry a chance of sprinkles across the whole cwa for the first part of the morning, then focus slight chance/chance pops across eastern WI for the rest of the day. Patchy fog in NC/C WI should mix out early. Look for mostly cloudy skies to prevail in eastern WI, while our western counties become partly cloudy. High temperatures should reach the middle 60s to lower 70s. A chance of light showers or sprinkles may persist into the evening across east central WI, otherwise skies will become partly cloudy as weak high pressure moves into WI. Patchy/areas of fog should develop after midnight, especially over NC/C/far NE WI. Lows will be mostly in the 40s and lower 50s. On Wednesday, a pleasant early fall day is in store, as high pressure brings abundant sunshine, along with temperatures warming into the lower to middle 70s. Long Term...Wednesday Night Through Monday Dry and above normal temperatures are expected to end the work week. Chances for precipitation return this weekend as the northern periphery of what is expected to become Hurricane Helene spread over the region, however, given that this storm is still in it`s infancy there is considerable uncertainty with its track. Precipitation...An upper-level ridge over the western Great Lakes Thursday and Friday will keep the region dry to end the week. Attention then shifts to what are expected to be the remnants of Hurricane Helene. As would be expected with a tropical system 4 to 5 days out there is considerable uncertainty, but long range models generally show Helene becoming a post-tropical depression as it meanders the Ohio and Tennessee Valleys Friday and Saturday. During this time northward moisture advection may bring the next chance (20- 40 %)for showers and a few thunderstorms, mainly to areas south of highway 29. LREF ensemble members show a large spread in expected rainfall amounts for this weekend with the most aggressive members showing a 5% chance for greater than 1 inch of rain through Saturday night. Beyond this weekend there are signs another short-wave may bring a chance for precipitation to the region early next week. Temperatures...More summer-like temperatures are expected to return for the back half of this week and this weekend as anomalously warm 850mb temperatures (1 to 2 standard deviations above normal) move over the region. Highs are forecast to reach the low to upper 70s each day with a slight chance (5-10%) for locations in the Fox Valley and central WI to reach 80. However, if the cloud shield from Helen spreads over the region Friday into this weekend high temperatures may trend a few degrees cooler than currently forecast. Overnight lows are also expected to trended warmer later this week which for those locations that have not yet seen frost will keep the growing season going until at least the end of September. && .AVIATION...for 12Z TAF Issuance Issued at 629 AM CDT Tue Sep 24 2024 We are seeing some patchy MVFR ceilings early this morning, especially near an inverted surface trough in eastern WI. Expect the low clouds to persist through the morning, then gradually rise to VFR by afternoon. In addition, scattered showers are possible in eastern WI, with the best likelihood of occurrence at the MTW TAF site. Expect clearing to occur as high pressure builds into the region later this afternoon and evening, with areas of ground fog developing overnight. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kieckbusch/GK AVIATION.......Kieckbusch