Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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148 FXUS63 KGRB 221758 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 1258 PM CDT Sun Sep 22 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Gusty north winds and building waves this afternoon into Monday morning will result in hazardous conditions for small craft. Dangerous swimming conditions on the beaches of Lake Michigan, mainly south of Sturgeon Bay. A Small Craft Advisory and Beach Hazard Statement remains in effect. - Areas of showers and a few storms end from northwest to southeast today. Mainly dry conditions are expected the rest of the week. - Patchy to areas of frost are expected across north central WI Monday morning. - Temperatures will return closer to normal today into middle of next week, before trending well above normal again late next week where high temperatures could run as much as 10 to 15 degrees above normal. && .DISCUSSION... Issued at 353 AM CDT Sun Sep 22 2024 Short Term...Today...Tonight...and Monday Main forecast concerns revolve around pinning down the best chances for showers and storms today, fog/frost potential tonight and temps. Showers/Storms & Clouds: Last of the showers/storms ahead of the front are coming to an end across eastern WI early this morning. Activity will turn to along/behind the front the rest of the morning and early afternoon, with a shortwave exiting the region. The heaviest activity is forecast to develop across east central WI later this morning, with some 0.50"+ amounts possible. Expect some mist/drizzle over the north early this morning as well. A ribbon of MUCAPE up to 1000 J/kg will slowly exit the area this morning and early afternoon, keeping thunder chances going, but nothing severe is expected. All of the activity will shift south of the area by 3-5pm, with dry conditions expected tonight into Monday. Clouds will slowly clear from northwest to southeast as the front exits, but likely not getting to near Manitowoc until around sunset. Could get a few daytime cu where there is enough surface heating behind the main batch of clouds. Skies will be mostly clear tonight with only a few high clouds over the south. Mostly sunny skies are expected for most spots on Monday, with a few daytime cu possible, along with some lake effect clouds over the east where delta Ts in the low teens and some lingering low-level moisture will remain in place. Temperatures / Frost & Fog Potential: The long stretch of well above normal temps comes to an end today, as 925mb temp drop to between 10-13C behind the front. Temps likely will be slow to climb this morning with the clouds/precip around, but as the clouds exit, we should be able to get into the mid 60s to around 70, with a few lower 60s in north central WI where temps aloft are the coolest. Temps will be pretty steady over far east central WI where clouds/precip will be around most of the day. Not much change in the airmass for Monday, so highs should be pretty close to today. Leaned toward the cooler guidance for tonight, which brings lows into the middle and upper 30s across much of north central WI. Would not be surprised to see some lower 30s in the typical cold spots. Will hold off a frost advisory as it looking more like patchy to areas of frost, but if lows drop a degree or two lower, widespread frost would be more likely. HRRR/SREF not highlighting much of a fog threat tonight, but think with the good radiational cooling, recent rain, mostly clear skies, light winds and a low- level inversion, should see at least some patchy ground fog early Monday morning. Long Term...Monday Night Through Saturday A fairly tranquil pattern is expected Monday night into Saturday. Some patchy fog (entire area) and patchy frost (far north) is possible Monday night. Meanwhile, a 500mb trough swinging across the western Great Lakes Tuesday will bring a small chance of showers across east-central Wisconsin. After the upper trough passage, 500mb ridging is expected across the Great Lakes which would result in temperatures returning to well above normal (10-15 degrees) levels by the end of the work week. The latest GFS guidance has some areas flirting with 80 on Thursday and Friday. There are some difference between the GFS/Canadian/ECMWF on how they handle the 500mb ridging, thus confidence is very low in the small chances of rain next Saturday. Beyond the forecast period, the 8-14 day outlook from the Climate Prediction Center is calling for a greater chance of above normal temperatures and a greater chance of below normal precipitation. Looking at past La Nina winters, which is expected this winter, there was a strong signal for the fall to be warmer than normal at Green Bay. && .AVIATION...for 18Z TAF Issuance Issued at 1258 PM CDT Sun Sep 22 2024 MVFR/IFR cigs were lingering at the east-central WI TAF sites early this afternoon in the wake of a cold front, with only a few light showers lingering along the lakeshore. As the front continues to slowly track southeast today, skies will clear from northwest to southeast. The lower cigs will linger the longest at the MTW TAF site before rising/clearing into this evening. Clear skies and good flying conditions are anticipated for tonight and Monday. Some patchy ground fog may develop in north-central WI early Monday morning. Northerly winds have increased early this afternoon, especially in central and north-central WI, where gusts to around 20 kts were observed. Expect these gusty winds to move into the east-central WI TAF sites this afternoon before decreasing everywhere this evening. && .MARINE... Issued at 353 AM CDT Sun Sep 22 2024 A period of hazardous conditions for small craft is expected this afternoon into early Monday as gusty north winds develop behind a cold front. A Small Craft Advisory remains in effect from this afternoon into Monday morning. There could be a brief period of winds to 20-25 kts later this morning as the initial surge of cold air advection arrives behind the front. Then as winds increase aloft, gusts to around 25-30 kts are expected this afternoon into early Monday. Waves will build be up to 4 ft on the bay and up to 6 ft on Lake Michigan, highest south of Sturgeon Bay. Winds and waves will slowly decrease Monday morning (north) and Monday afternoon (south). While winds will mainly be out of the north, there will be just enough of a easterly component to bring 3+ waves to the shores of Lake Michigan. This will create dangerous swimming conditions, mainly south of Sturgeon Bay. A Beach Hazards Statement remains in effect. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement through Monday morning for WIZ022. Beach Hazards Statement through Monday afternoon for WIZ040-050. && $$ DISCUSSION.....Bersch/Eckberg AVIATION.......Kruk MARINE.........Bersch