Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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647 FXUS63 KGRB 231136 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 636 AM CDT Mon Sep 23 2024 Updated aviation portion for 12Z TAF issuance .KEY MESSAGES... - Winds and waves will continue to decrease early this morning on Lake Michigan. A Small Craft Advisory remains in effect through 7AM south of Sturgeon Bay. Dangerous swimming conditions continue on the beaches of Manitowoc Co. through 7AM. - Patchy to areas of frost are expected across north central Wisconsin early this morning and possibly again Tuesday morning. A Frost Advisory remains in effect for portions of northern Wisconsin through 8AM. - Temperatures close to normal are expected today and Tuesday then above normal temperatures are expected into the weekend. High temperatures could run as much as 10 to 15 degrees above normal. Current high temperatures Thursday and Friday are in the 75-90 percentile range of the guidance values. && .DISCUSSION... Issued at 340 AM CDT Mon Sep 23 2024 Short Term...Today...Tonight...and Tuesday A fairly quiet start to the new work week. Main forecast concerns will be temp trends & frost potential, cloud trends, and small rain and fog chances. Cooler (but near normal) temps are on tap today and Tuesday. Early This Morning: Temps across north central WI have fallen pretty much as expected, with readings in the mid and upper 30s. The typical cold spots will bottom out in the low 30s. Will not make any changes to the frost advisory. Some ground fog also developed, mainly across north central WI, which will burn off shortly after sunrise. Rest of Today: A quiet mid-late September day is expected for the region as weak surface high pressure slides across the Great Lakes. A few daytime cumulus clouds, along with a few clouds off of Lake Michigan, are expected with high clouds increasing from the south during the afternoon. 925mb between 12-13C support highs in the mid 60s to around 70, which is near normal. Tonight: Dry conditions are expected for most/all of the area. Only thing to watch will be far east central WI where a pocket of deeper moisture will work northward overnight. Still some low- level dry air to contend with and better chances will stay to our south/east, but could see some light showers or sprinkles closer to Lake Michigan, along with more clouds. Mostly clear skies, light winds and a low-level inversion will once again promote some fog development overnight into early Tuesday, mainly across parts of central and north central WI. SREF showing less than 10% chance of visibilities 3 miles or less, with the HREF not supporting much fog either. Think the fog will once again be patchy ground fog and will burn off quickly after sunrise. Leaned toward the colder guidance for lows across north central WI, where clouds should be the highest/thinnest. Lows look to range from the mid 30s to low 40s (coldest in the typical cold spots) to the upper 40s and low 50s in the Fox Valley and lake shore. If clouds stay out of the north, another frost advisory may be needed, but lows look just slightly warmer than this morning. Tuesday: Weak surface low pressure will track into southern Lake Michigan, as a upper trough drops across the western Great Lakes. This will bring more clouds to the region, along with low chances (under 25%) mainly across far eastern WI. 925mb temps do not change much, so highs should be similar to today, with perhaps slightly cooler readings closer to Lake Michigan due to more cloud cover. Long Term...Tuesday Night Through Sunday After a couple of days with near normal temperatures, above normal temperatures will return Wednesday and continue into next weekend. The upper trough across the central United States Tuesday is going to evolve into a closed low over Missouri and Arkansas with 500mb ridging across the western Great lakes into Thursday. It gets interesting Thursday as the models are depicting a tropical system moving northward across the Gulf of Mexico with a landfall across the eastern Gulf Coast states. The remnants of the tropical system will then dumbbell around the closed low across Arkansas Thursday night into Saturday. The GFS/Canadian models brush our southern counties with some light rain with this feature. However, the ECMWF is much more pronounced with the 500mb ridge across the Great Lakes, leaving the area dry Saturday with a small chance of showers on Sunday. With ridging across the area, expecting mostly clear skies and light winds during the night which may result in some patchy fog during the overnight hours to a few hours after sunrise each morning. Expecting a larger than normal diurnal range each day as well due to the dry air mass and longer nights. Guidance values would suggest highs Thursday and Friday will run 10 to 15 degrees above normal, which was in the 75 to 90 percentile of all guidance values. Guidance values for next weekend are heavy weighted toward climatology, which now would be highs in the 60s. Do expect high temperatures to go up a few degrees in the coming days. && .AVIATION...for 12Z TAF Issuance Issued at 636 AM CDT Mon Sep 23 2024 Patchy ground fog will mix out early this morning across central and north central WI. Otherwise, look for VFR conditions today into this evening, with some clouds coming off Lake Michigan and daytime cumulus clouds later this morning and afternoon, along with some high clouds at times. Patchy ground fog will again be possible late tonight into early Tuesday, especially across central and north central WI. Slight chance of a shower or sprinkle across east central WI late tonight, but no aviation impacts are expected. Light winds below ~10 knots are expected during the TAF period. && .MARINE... Issued at 340 AM CDT Mon Sep 23 2024 Winds have dropped under criteria across the bay and nearshore waters of Lake Michigan early this morning. However, high wave action continues on Lake Michigan. The mid-late buoy is still at 4ft at 3AM, with a SPOT buoy off of Two Creeks is reporting waves around 5 ft around 3AM, which the wave model has captured very well. As waves slowly subside, will cancel the Small Craft Advisory for the bay and north of Sturgeon Bay on Lake Michigan at 09z and continue it south of Sturgeon Bay through 12z when waves will drop under 4 ft. As waves continue to subside this morning, the threat for dangerous currents will end as well, with the higher waves expected to be closer to the open waters. Manitowoc Co. will still see a high swim risk through 7AM. Otherwise, the swim risk will remain in the moderate category this morning. Will cancel the Beach Hazards Statement for Door and Kewaunee. && .GRB WATCHES/WARNINGS/ADVISORIES... Frost Advisory until 8 AM CDT this morning for WIZ005-010>012- 018-019. Beach Hazards Statement until 7 AM CDT this morning for WIZ050. && $$ DISCUSSION.....Bersch/Eckberg AVIATION.......Bersch MARINE.........Bersch