354 FXUS63 KGRB 161800 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 100 PM CDT Sun Oct 16 2022 Updated aviation portion for 18Z TAF issuance .SYNOPSIS... Issued at 524 AM CDT Sun Oct 16 2022 A significant early-season snow in the Lake Superior snowbelt tonight into Monday. Otherwise, scattered showers today, then windy and colder with scattered rain and snow showers Monday. Chilly conditions continuing through most of the upcoming work week before warmer weather returns next weekend. A highly amplified large scale pattern with a western ridge and Great Lakes region upper trough will remain in place through most of the upcoming work week. The upper pattern is then expected to transition fairly quickly to a western trough/eastern ridge configuration. Temperatures will remain below normal through most of the upcoming work week before warming sharply to considerably above normal next weekend when the upper flow backs southwest. Precipitation across most of the area will be below normal, though near-to- perhaps slightly above normal amounts are possible in the Lake Superior snowbelt. A wetter regime for the whole area will probably develop just beyond the end of the period, once the SW flow becomes established and has time to advect gulf moisture into the region. && .SHORT TERM...Today...Tonight...and Monday Issued at 524 AM CDT Sun Oct 16 2022 Opted to post the initial advisory/warning headlines for the upcoming lake-effect snow event with the morning issuance. The specific snow amounts will still need tweaking, and it remains to be seen if the significant snow showers drive far enough inland to warrant an expansion of the advisory another tier of counties south and east. Later forecasts can make those adjustments if necessary. The lake snow setup for tonight into Monday is pretty impressive. The BUFkit lake-effect perspective indicated lake-induced instability will result in ELs AOA 12K ft at KIWD from late this afternoon until Monday afternoon, with LI CAPEs topping out over 800 J/kg for a few hours. The low-level wind direction will be favorable for getting lake bands into Vilas County through tonight, though the flow aloft may back a little too NE to be ideal on Monday. However, some snow bands should still continue to reach Vilas county Monday, and strong winds aloft are likely to mix down to the surface as gusts to 35 mph. Given the anticipated snowfall totals, blowing and drifting snow, and this being the first significant winter event of the season seemed more than sufficient to justify going with a warning. Similar reasoning was used to justify the advisory for the border areas, even though totals are currently a little below what would normally warrant an advisory. Strong destabilization as the cold air flows over the warm waters of the Bay of Green Bay will likely mix at least 40 kt gusts to the surface, and would not be surprised to see a few gusts approaching 50 kts over the northern part of the Door. So, posted a Wind Advisory for the Door to match the Gale Warning for the adjacent waters of the bay and lake. Freezing temperatures are unlikely over the Door tonight, so dropped the FZ.A there. Not sure if Kewaunee or Manitowoc will freeze either (it will be close), so just left the FZ.A run there. Overall, was looking for the simplest path forward with the Freeze headlines as doubt there is much utility left in issuing those now that it's mid-October and we've transitioned into an early winter pattern. .LONG TERM...Monday Night Through Saturday Issued at 322 AM CDT Sun Oct 16 2022 Main forecast concerns to be timing the demise of the lake effect snows across northern WI and how far to take temperatures up at the end of the week. Monday night and Tuesday... Lake effect snow showers are expected to carry over into Monday evening, however be in a diminishing phase as drier air begins to advect into the region from high pressure over the central CONUS. Look for additional accumulations over Vilas County to be under an inch with little if any accumulation farther south or east. Otherwise, partly to mostly cloudy skies and blustery conditions are forecast for Monday night with min temperatures in the middle to upper 20s central WI, upper 20s to lower 30s eastern WI. Lingering cyclonic flow could still help to produce a few snow showers or flurries over northern WI into Tuesday. The rest of northeast WI should be dry with partly to mostly cloudy skies as the ridge of high pressure edges eastward into the Upper MS Valley. Tuesday will still be quite blustery, especially over eastern WI where gusts to be over 30 mph. Max temperatures on Tuesday to range from the middle to upper 30s north-central WI, to the middle 40s east-central WI. Tuesday night and Wednesday... The last of any lake effect snows should end Tuesday night as the cyclonic flow weakens, the surface ridge slowly approaches and wind trajectories become less favorable. Still think lake clouds will drift into northern WI, thereby keeping skies mostly cloudy. Areas farther south should see partly cloudy skies. In addition, winds should finally begin to subside overnight with gusts falling below 20 mph. Min temperatures to be in the lower to middle 20s central WI, upper 20s to lower 30s eastern WI. The surface ridge is forecast to weaken by the time it reaches the western Great Lakes region on Wednesday. There could be some clouds passing through as a northwest flow aloft persists and weak shortwaves drop southeast within the flow. No precipitation anticipated and with west winds bringing WAA back to WI, look for temperatures to modify a bit. Max temperatures Wednesday to be in the upper 30s to lower 40s north, lower to middle 40s south. Wednesday night and Thursday... Models are in good agreement with the passage of a cold front late Wednesday night. Gulf moisture is practically non-existent, thus do not see any precipitation with this front. We should see a modest increase in clouds with a wind shift to the west-northwest. A rather weak surface ridge is forecast to slide into the region on Thursday which will bring partly sunny skies to northeast WI. Max temperatures for Thursday to be in the middle to upper 40s north, upper 40s to lower 50s south. Thursday night and Friday... A return flow develops across WI Thursday night as the ridge shifts to the east. There is some model issues with the movement of the next cold front on Friday. The GFS/CMC both send this front through WI, while the ECMWF essentially wipes the front out. Once again, the atmosphere is too dry to sustain any precipitation, so dry conditions should prevail. The issue would be on temperatures as the GFS/CMC solution would be cooler than the ECMWF (especially the CMC). For now, have max temperatures Friday in the lower to middle 50s north, upper 50s to lower 60s south. Friday night and Saturday... Dry and mild conditions are forecast across the region going into next weekend as a southerly flow pulls warmer air northward. Max temperatures on Saturday to reach the upper 50s to around 60 degrees north/near Lake MI, lower to middle 60s central/east- central WI. && .AVIATION...for 18Z TAF Issuance Issued at 100 PM CDT Sun Oct 16 2022 Northwest flow across Lake Superior will keep cloud cover in place through the next few days. Ceilings will mainly range between MVFR and VFR, with the lower ceilings generally ranging north of a line from AUW to IMT. Lake effect will bring showers to far northern Wisconsin throughout today, and scattered shower activity also seems likely at times through the rest of the area. Any shower activity could briefly bring some MVFR/IFR ceilings and brief lower visibility. Tonight, gusty winds will move into the region and last well into Monday. Expect strong gusts up to 30 to 35 mph at times by Monday morning through Monday afternoon. Lake effect snow will also develop across far northern Wisconsin tonight, and last into Monday. The wind and heavy snow will pose a hazard for LNL and D25 and some lighter snow could reach as far as RHI. && .GRB WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 7 PM this evening to 7 PM CDT Monday for WIZ005. Winter Weather Advisory from 7 PM this evening to 7 PM CDT Monday for WIZ010-011. Wind Advisory from 4 AM Monday to 7 PM CDT Tuesday for WIZ022. && $$ SYNOPSIS.......Skowronski SHORT TERM.....Skowronski LONG TERM......Kallas AVIATION.......Uhlmann