Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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892 FXUS63 KGRB 242318 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 618 PM CDT Tue Sep 24 2024 Updated aviation portion for 00Z TAF issuance .KEY MESSAGES... - Warm temperatures to prevail through the end of the work week, with highs running between 10 to 15 degrees above average. - Next chances for precip arrive Sunday into Monday as the remnants of what is expected to become Hurricane Helene traverse the Midwest. && .DISCUSSION... Issued at 218 PM CDT Tue Sep 24 2024 Short Term...Tonight and Wednesday A surface low moving from northwest Indiana to central Lower Michigan will produce clouds across the lakeshore counties and parts of the Fox Valley tonight, while scattered to broken clouds dissipate further west. Clearing skies should allow for the ground fog mostly east of highway 51 and west of the bay. Lows tonight will be around five degrees higher than normal. Surface ridging will move into Wisconsin Wednesday, and bring sunny skies and mild temperatures, once any ground fog dissipates. Highs will be 5 to 10 degrees higher than average,. Long Term...Wednesday Night Through Tuesday Expect the beginning of the extended to be warm and dry as a rex blocking pattern maintains ridging over the eastern CONUS. Focus will then turn to precip chances this weekend into early next week as the northwestern periphery of what is expected to become Hurricane Helene makes its way up into the Midwest. However, there is still considerable uncertainty with storm track given the extended lead-time. Precip chances... As the rex block gradually breaks down and shifts to the east, ensembles show Helene becoming a post- tropical depression as it propagates across the Ohio River Valley Sunday and Monday. There are still some questions about how much moisture will be able to make it up into Wisconsin during this time, with current model guidance appearing pessimistic about any moisture transport north of Highway 10. Better chances for rain/storms look to be Monday evening through Tuesday as a Canadian low drags a cold front southeast through the Great Lakes. Models show the surface low ingesting residual moisture from Helene, resulting in around 1.75" PWATs (~2 to 3 standard deviations above average) extending across eastern Wisconsin out ahead of the front. There is still considerable spread in precip amounts this far out, although there seems to be a signal for heaviest rainfall occurring near/along the lakeshore. Some rumbles of thunder cannot be ruled out across central Wisconsin Monday evening as MUCAPEs approach 200 J/kg, although storm coverage is expected to be isolated. Temperatures... Summer-like conditions are expected to make a brief comeback for the latter half of the week as 850 mb temperatures rise to between 15 and 17C Friday and Saturday. Subsidence from high pressure will thus result in highs running around 10 degrees above average, ranging from the mid to upper 70s across the forecast area. This being said, temperatures may underperform Friday and Saturday as the cirrus shield from Helene spreads over the region. Post-frontal temperatures will then drop down into the low to mid 60s Tuesday afternoon, reading near to slightly below average for late September. && .AVIATION...for 00Z TAF Issuance Issued at 618 PM CDT Tue Sep 24 2024 A surface low moving from southern lower Michigan to northern Lake Huron will bring clouds with MVFR ceilings at times south of a SUE to ATW to Y50 line tonight. Stratocumulus clouds with bases between 4000 and 6000 feet will gradually dissipate around sunset. Ground fog is possible after midnight in an area roughly east of a EGV to AIG to DLL line, and west of a SAW to EZS to STE line. The fog will dissipate around 13z if it does form. Sunny skies and good visibility is expected Wednesday as a ridge of high pressure builds into the region. && .GRB WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION.....RDM/Goodin AVIATION.......Kurimski