671 FXUS63 KGRB 091751 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1251 PM CDT Tue Oct 9 2018 Updated aviation portion for 18Z TAF issuance .SHORT TERM...Today...Tonight...and Wednesday Issued at 341 AM CDT Tue Oct 9 2018 Heavy rain potential will continue through the short-term portion of the forecast, especially over central and north-central portions of Wisconsin. The Flood Watch continues for locations to the northwest of a line from roughly Northern Marinette County to Portage County. Satellite imagery and surface observations continue to show widespread cloud cover across much of the Western Great Lakes region, with the exception of a few breaks in the clouds over southeastern WI. Radar trends continue to show moderate to occasionally heavy showers and thunderstorms sliding across central and north central WI and to the southwest into IA. Additionally, surface observations and webcams continue to show patchy to widespread fog from Brown County to Marathon County and points northward. Visibility around a mile or less at times has been the rule across those areas. Today: A nearly stationary front in place across the CWA will lift very slowly northward into this afternoon. Initial showers and isolated thunderstorms this morning will slide out of the area by roughly mid morning before more, mainly scattered rain showers slide into central and north central WI. Farther southeast, as the front lifts northward, skies may clear a bit toward the afternoon hours. As this happens, models are hinting at an increase in instability across the Fox River Valley. This increase in instability along with shear in the 20 to 30 knot range will lead to some stronger storms across those area this afternoon. The main threat will be strong gusty winds in the strongest storms along with small hail. Outside of any stronger thunderstorms that form, the widespread moderate to heavy rainfall will likely decrease in coverage through much of today, even though there will likely be some scattered lighter rain showers that linger over the northwest half of the CWA. Tonight into Wednesday: An intensifying low pressure system will slide from the central Plains northeast to Upper Michigan through this time period. As this happens, added upper level energy will slide through the area, following roughly the same path. Ahead of the low, isentropic upglide will increase this evening along with deeper moisture on the 300K isosurface. This isentropic upglide will be enhanced by a developing LLJ to around 40 kts. Aloft, much of the CWA is progged to be in the right entrance region of an associated upper-level jet also leading to increased ascent. These features will come together to produce the potential for heavy rainfall across the northwestern half of the CWA, where the Flood Watch is in effect. Models are painting out around 1 to 3 inches across much of the CWA with totals possibly approaching 4 inches from around Florence County to Marathon County and points to the northwest. As the low lifts into Upper Michigan Wednesday, the cold front will sweep across the CWA, bringing and end to the heaviest rainfall by late Wednesday afternoon into Wednesday evening, from west to east. Temperatures will differ drastically from northwest to southeast across the CWA today through Wednesday. The southeast half of the CWA will likely see highs in the low to mid 70s, while the northwestern portion of the CWA sees highs mainly in the upper 40s to low 50s. .LONG TERM...Wednesday Night Through Monday Issued at 341 AM CDT Tue Oct 9 2018 After a period of mild temperatures through the middle of the week, a deep trough will slowly move across the region, bringing below normal temperatures through the end of the forecast period. Forecast concerns mainly revolve around temperatures, as well as rain chances this weekend. Wednesday night through Thursday night...Low pressure will be exiting northeast WI during the evening, which will keep a high chance of rain over the far north and along the lakeshore through midnight. Meanwhile, mid-level dry slotting will be moving in behind the low across north-central WI during the evening, and eastern WI overnight. The dry slot will end precip across eastern parts of the state. However, wrap around moisture within the comma head of the cyclone will likely graze north-central WI overnight into Thursday morning, which could lead to spotty light rain and possibly a few flakes. Should see ample cloud cover on Thursday within a much colder airmass and lingering cyclonic flow. Highs will likely fall back into the 40s for most locations, though some locations over the northwoods may struggle to get out of the 30s. Guidance shows clouds will slowly depart to the northeast on Thursday night. But even with the clearing skies, a decent pressure gradient will remain in place that will likely limit frost potential over eastern WI. Otherwise, with temps fall into the low to mid 30s, a freeze will be possible across the Fox Valley and Lakeshore. Rest of the forecast...High pressure will quickly move into the region on Friday before shifting east on Saturday. Should see more sunshine on Friday but with cool temps. Lighter winds on Friday night will promote another round of frost/freeze over the Fox Valley and Lakeshore. As return flow sets up on Saturday ahead of a front that moves into the northern Mississippi Valley, should see clouds return though precip chances will likely hold off until Saturday night and Sunday. Precip chances look relatively high during this time, especially over northeast WI, as low pressure travels south of the region. Another cool airmass will build in behind the system for the start of the next work week. && .AVIATION...for 18Z TAF Issuance Issued at 1249 PM CDT Tue Oct 9 2018 A quasi-stationary front will continue to separate low clouds and fog from more summer-like cumulus field with no fog. For the RHI, AUW and CWA TAF sites, expect mainly IFR conditions to prevail over the next 24 hours with periods of rain showers. For the ATW, GRB and MTW TAF sites, VFR conditions are expected for the rest of this afternoon, before cigs/vsbys gradually drop into the IFR category by mid-evening. Scattered thunderstorms are expected this afternoon over eastern WI where instability is stronger. Thunderstorms are also possible on Wednesday over all of northeast WI as a cold front pushes into the region. A low-level jet will develop tonight at each TAF site, resulting in LLWS. && .GRB WATCHES/WARNINGS/ADVISORIES... Flood Watch through Wednesday evening for WIZ005-010>013-018>021- 030-031-035-036. && $$ SHORT TERM.....Cooley LONG TERM......MPC AVIATION.......Kallas