Area Forecast Discussion
Issued by NWS Green Bay, WI

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831 FXUS63 KGRB 191709 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1209 PM CDT Mon Apr 19 2021 Updated aviation portion for 18Z TAF issuance .SHORT TERM...Today...Tonight...and Tuesday Issued at 419 AM CDT Mon Apr 19 2021 A cold front was moving through eastern WI early this morning. The front, in concert with a short-wave trough and LFQ of an upper level jet, was producing a band of rain showers. Radar showed the showers quickly exiting the region. Lake-enhancement due to cool northwest flow off Lake Superior was also producing light snow showers or mixed precipitation in north central WI. Expect abundant cloud cover to linger over the forecast area today, as an upper level trough remains over the western Great Lakes. Lake-enhanced snow showers should persist over Vilas County, with isolated diurnally-driven rain or snow showers redeveloping elsewhere during the afternoon. Significantly cooler conditions are anticipated, with highs in the middle 30s to middle 40s. Blustery northwest winds will gust to around 25 mph, before tapering off early in the evening. Lingering showers should taper off this evening, with skies becoming partly cloudy overnight. Low temperatures are expected to drop into the upper teens and 20s. On Tuesday, expecting somewhat of a repeat performance (minus the gusty winds), with mostly cloudy skies, cool temperatures and isolated afternoon rain or snow showers. Highs will be in the middle 30s to middle 40s. .LONG TERM...Tuesday Night Through Sunday Issued at 419 AM CDT Mon Apr 19 2021 No major systems forecast to impact the area through the weekend. Upper trough will provide for north/northwest flow and cloudy/cool conditions through mid-week then a more zonal flow sets up bringing in a warmer Pacific airmass for the end of the week. Still some questions on how that pattern will play out late this week and into the weekend, impacting precip chances and temps. Tuesday night into Wednesday...upper level trough will be firmly planted over the Great Lakes. Some breaks are possible in the overcast, but mostly cloudy skies look to prevail most of the time. The cyclonic flow, cold air aloft, lingering moisture, and a weak shortwave or two, could kick off some light/spotty rain or snow shower or sprinkle/flurry activity, especially on Wednesday. Some disagreement in just how much low-level moisture will remain, which leads to questions if there is enough moisture/lift to squeeze out some precip. GFS is the most bullish, showing up to a tenth of QPF over parts of central WI. Won`t go that far, but will add slight chance PoPs, as the combination of available moisture, upper trough overhead, cold air aloft, steep low level lapse rates and a weak shortwave should provide enough support for at least some spotty precip activity. Well below normal temps will continue as it will be another cold/chilly night, with lows in the teens and 20s. If skies clear out more than anticipated, the typical cold spots could drop closer to 10 degrees. Highs look to be similar to Tuesday, but perhaps slightly warmer, with most spots in the 40s. Thursday into Friday...the upper trough will continue to shift toward the East Coast, finally loosening its grip on the area and allowing ridging to build into the Great Lakes. It looks to be dry from Thursday into Friday morning, then models are signaling some WAA precip possibly spreading into the area later on Friday, along with some possible precip associated with an approaching trough and cold front from the west. Model blend paints some low- end PoPs starting Friday afternoon and can`t really argue with that at this point. As the flow turns more zonal, a push of Pacific air will spread into the area. Highs look to jump 10-15 degrees compared to Wednesday, with most spots seeing highs in the 50s to near 60. Depending on cloud cover and possible precip, we could see some spots climb over the 60 degree mark. Saturday and Sunday...the forecast gets more and more murky as models diverge on how the overall pattern will play out. Timing differences are a plenty regarding the frontal boundary, how chilly the air is behind it and how fast the WAA occur ahead of another system to our west occurs. Will continue to stick with the model blend for now, which keeps chance PoPs through Saturday but keeps Sunday dry and temps near or slightly below normal. && .AVIATION...for 18Z TAF Issuance Issued at 1203 PM CDT Mon Apr 19 2021 Scattered snow showers will continue across the far north into this evening with isolated rain or snow showers over the remainder of the area this afternoon. Most CIGS will be in the VFR category with MVFR CIGS at times in the rain or snow showers. Clouds will be on the decrease tonight with VFR conditions through Tuesday afternoon. Gusty northwest winds may gusts to around 30 knots this afternoon will quickly subside around and just after sunset. Northwest winds are expected on Tuesday, although could swing around to the northeast or east during the afternoon at KGRB/KATW/KMTW. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....Kieckbusch LONG TERM......Bersch AVIATION.......Eckberg

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