Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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115 FXUS63 KGRB 191917 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 217 PM CDT Wed Jun 19 2024 Forecast discussion for routine afternoon forecast issuance .KEY MESSAGES... - Chance of showers and thunderstorms mainly across east-central Wisconsin tonight. - Chance of more showers and storms area-wide on Thursday. - An active pattern is expected to continue through the end of this week and into this weekend. Stronger storms and locally rainfall will be possible each day, with the greatest risk for excessive rainfall coming Friday and Saturday. && .DISCUSSION... Issued at 217 PM CDT Wed Jun 19 2024 Short Term...Tonight and Thursday Main forecast concern remains on precipitation trends over the next 24 hours as a frontal boundary to linger to our south and a shortwave moves into northern sections of the Great Lakes. The 19Z MSAS surface analysis showed a cold front that extended from roughly MNM-Y50-DBQ. High pressure was situated over northern sections of the northern Plains/Upper MS Valley. The radar mosaic indicated scattered showers and thunderstorms across the southeast half of WI ahead of the cold front where sufficient instability and shear present. The cold front is forecast to move across the rest of east-central Wisconsin this evening and then stall near the IL border later tonight. The proximity of the front is close enough such that a chance of showers and thunderstorms will need to be kept in the forecast across parts of central and east-central WI, mainly south of Hwy 54. Meanwhile, the high pressure will move into northern sections of the Great Lakes and keep northern WI dry tonight. Cooler/less humid air mass to settle over northeast WI tonight with min temperatures to range from the lower to middle 50s north, to the upper 50s to lower 60s south. Models hint at this stalled boundary will begin to slowly lift back north as a warm front on Thursday, but remain south of the forecast area. A mid-level shortwave is expected to move northeast into the western Great Lakes in the afternoon. Between these two features, the chance for showers and thunderstorms will be on the increase, mainly during the afternoon. The combination of clouds, precipitation chances and an east-northeast wind will keep temperatures below normal on Thursday. Look for readings to only reach the upper 60s to lower 70s. Long Term...Thursday Night Through Wednesday Despite high pressure over the northern Great Lakes region, isentropic lift north of a warm front over the southern Great Lakes will bring the chance for showers and thunderstorms to the region Thursday night. This warm front will then lift north on Friday into southern Wisconsin, with increased chances for precipitation across the region. Although there will be modest instability of a few hundred J/kg of MUCAPE, the best instability will be well to our south along with the severe weather risk. However, heavy rainfall and some minor flooding will be a risk with long skinny CAPE profiles and PWAT values of 1.75 to 2 inches. The warm front will linger across Wisconsin Friday night and Saturday, with additional chances for moderate to heavy rainfall. Instability will remain fairly meager across our area, keeping the severe weather threat minimal. However, the continued threat for several rounds of rainfall will increase the flood threat as repeated rounds of moderate to heavy rain cause rivers and streams to rise to or near bankfull. The region is in a slight risk for excessive rainfall Friday and Saturday. Probabilistic guidance indicates there is a 30 to 40 percent chance of exceeding 2 inches of rain Friday and Saturday, with the highest chances across central and north-central Wisconsin. A cold front will then sweep through the area Saturday night, which will end the threat for moderate to heavy rain across the region. Although additional light showers are possible on Sunday, this activity is not expected to exacerbate the flooding threat like the previous activity. Next week will start out dry, with additional chances for rain Tuesday and next Wednesday as several weak low pressure systems track through the area. Next week will bring a return to warmer weather as daytime highs soar into the 80s with a few 90 degree readings possible, especially across central and east-central Wisconsin. && .AVIATION...for 18Z TAF Issuance Issued at 1242 PM CDT Wed Jun 19 2024 MVFR cigs to exist behind a cold front that extends from far northeast to southwest WI. These lower cigs are expected to rise into the lower VFR category later this afternoon as the cold front sags into southern WI. Scattered showers and isolated thunderstorms are expected to accompany the cold front and impact mainly east-central WI. This cold front is forecast to stall near the IL border tonight and may try to lift back north a bit as a warm front on Thursday. Meanwhile, an upper-level disturbance is forecast to move into northern sections of the Great Lakes on Thursday. These two features will bring additional chances for showers and storms across northeast WI, especially during the afternoon. MVFR conditions south of a SUE to AUW line are expected on Thursday with low clouds along the Lake Michigan shore, with IFR conditions possible at MTW and SUE. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....Kallas/Kurimski AVIATION.......Kallas