Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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176 FXUS63 KGRB 271736 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1236 PM CDT Mon May 27 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - There will be additional rounds of showers and a few thunderstorms across the region today through Tuesday. Severe weather is not anticipated. - A few rivers across central and eastern Wisconsin will remain above bankful the next few days. - Areas of patchy frost are possible Wednesday night into early Thursday morning across far northern Wisconsin. && .DISCUSSION... Issued at 301 AM CDT Mon May 27 2024 Short Term...Today...Tonight...and Tuesday A low pressure system, seen spinning just off the coast of Manitowoc on satellite and and radar imagery, will continue to slowly move east towards lower Michigan this morning. Since the low is moving slowly, rain showers will continue through much of the morning across northeast Wisconsin and the lakeshore counties. Additional rainfall amounts across this area could reach one half up to an inch this morning, with the highest amounts across Door County where rain will linger the longest. This additional rainfall may cause localized flooding; however, the rain is more light to moderate versus heavy which should help mitigate flash flooding. Meanwhile, a weak shortwave will track through the upper Mississippi Valley this afternoon around a larger upper low situated across southern Canada. This will bring the chance for showers and a few thunderstorms to much of the area this afternoon and this evening. MUCAPEs of only a few hundred J/kg will mean non-severe thunderstorms are expected with this activity. A more substantial mid level positively tilted trough and vigorous shortwave will approach northern Minnesota late tonight and slowly dig across the western Great Lakes region on Tuesday as it spins off from the main low. This will bring the chance for showers across north-central Wisconsin late tonight and across the rest of the region on Tuesday. Modest MUCAPEs of a few hundred J/kg will once again mean non-severe thunderstorms will be possible as this trough tracks through the area. Abundant cloud cover will keep temperatures below normal today, with highs mainly in the 60s. Lows tonight are expected to range from the upper 40s across the north to the lower 50s across east-central Wisconsin. Highs on Tuesday will once again be cool given the abundant cloud cover and rain expected during the day, with temperatures ranging from around 60 across the north to the middle 60s across east-central Wisconsin. Long Term...Tuesday Night Through Sunday An upper ridge is forecast to move from the northern Plains into the Great Lakes region during the Wednesday-Friday time frame and provide for a much needed break from the rain. This ridge shifts east and weakens, allowing for a return of gulf moisture and an eastward moving shortwave trough to move into WI with our next chance for showers Friday night through Saturday night. Temperatures will continue below normal through mid-week, then become closer to normal late week. Tuesday night and Wednesday... Light showers look to carry over into Tuesday evening, mainly over central/east-central WI as the shortwave trough to still be in the process of exiting the area. High pressure stretching from western Ontario through the Upper MS Valley will begin to build into WI later Tuesday night bringing a decrease in clouds. Min temperatures to range from the middle to upper 30s north-central WI, to the middle to upper 40s over east-central WI. Perhaps a little patchy frost over the colder locations of the Northwoods. This ridge of high pressure moves into the western Great Lakes on Wednesday and should bring mostly sunny skies and a north wind at 5 to 10 mph. Air mass aloft is still a bit on the cool side (8H temperatures around +5C), thus expect max temperatures to be in the lower 60s near Lake MI, middle 60s to around 70 degrees inland. Wednesday night and Thursday... Models hardly move this high pressure through Wednesday night. The combination of cool air aloft, a dry air mass in place and light winds will allow temperatures to quickly fall through the night. Parts of northern WI could see min temperatures in the lower to middle 30s and the possibility of frost developing. Central and east-central WI are expected to stay frost-free with temperatures falling into the lower to middle 40s. As the high pressure starts to slowly shift east on Thursday, winds will turn to the south- southeast by the afternoon and begin to tap slightly warmer air. A dry air mass overhead will help temperatures recover despite the cool start to the day. Look for max temperatures in the middle 60s near Lake MI, mainly lower to middle 70s inland. Thursday night and Friday... The high pressure moves toward the eastern Great Lakes by Friday, while an upper ridge moves into the western Great Lakes. Even with a push of WAA, the air mass over northeast WI remains too dry to support any precipitation, thus dry conditions should continue through Friday. Do anticipate some increase in clouds by Friday afternoon between the persistent WAA, a gradual increase in moisture and a mid-level shortwave trough that will push into the northern Plains. Max temperatures on Friday to be in the upper 60s near Lake MI, lower to middle 70s north and middle to upper 70s south. Friday night and Saturday... Questions remain as to how soon to bring precipitation chances back to northeast WI as models continue to disagree on timing/ movement of the shortwave trough, as well as how fast can the atmosphere saturate. Models tend to underestimate the lingering dry air and send precipitation too far to the east. That being said, do expect to see a band of showers move across the Upper MS Valley into at least western WI Friday night, then sweep across the rest of WI on Saturday as the shortwave trough arrives and a weak cold front traverses the area. Max temperatures Saturday to be in the upper 60s lakeside, around 70 degrees north-central WI and lower to middle 70s elsewhere. Saturday night and Sunday... Uncertainty persists going into the latter part of the weekend as models differ on the strength of the shortwave trough. A weaker, progressive trough would exit Saturday night with a dry Sunday. A stronger, slower moving trough would keep precipitation in the forecast through Sunday. Have followed the model blend which does keep a mention of showers on Sunday. && .AVIATION...for 18Z TAF Issuance Issued at 1235 PM CDT Mon May 27 2024 Showers and MVFR conditions will exit the northern Door Peninsula early this afternoon. The remainder of the forecast area will have broken clouds and scattered showers as an upper level disturbance approaches the area. Isolated thunderstorms could produce brief IFR conditions and surface wind gusts to 35 knots. Scattered showers and VFR/MVFR conditions are expected overnight and Tuesday, as another upper level disturbance moves across the region. Isolated thunderstorms are possible Tuesday afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kurimski/Kallas AVIATION.......RDM