978 FXUS63 KMKX 092257 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 557 PM CDT Tue Oct 9 2018 .UPDATE... Diurnal convection is scattered across southern Wisconsin early this evening. The stronger/severe convection has stayed up along the stationary surface boundary stretching from near Prairie du Chien, northeast through Marquette/Green Lake county. Effective deep layer shear along this region is better than 40kts, combined with MUCAPE of 1000-1500J/KG. Many of the storms have had impressive rotation across Iowa, Sauk and Marquette counties, but so far we haven't had a solid confirmation of any touchdowns. We should see a rather quick downward trend in the activity with the loss of daylight. The area should then get quiet for a time before more showers and storms push in with the larger synoptic system on Wednesday. && .AVIATION(00Z TAFS)... Showers and storms early this evening will diminish quickly by mid evening. We should then get rather quiet until after about 12z on Wednesday. That's when the showers and storms associated with an advancing cold front begin to overspread southern Wisconsin. Look for VFR conditions through the overnight hours, though any storms could bring briefly lower conditions. MVFR then IFR CIGS/VSBYS will quickly overspread southern Wisconsin by mid morning on Wednesday, remaining low through the day as the slow moving storm system tracks across the region. Improving conditions are expected Wednesday evening as winds turn westerly and pull in much drier air. && .PREV DISCUSSION... (Issued 252 PM CDT Tue Oct 9 2018) DISCUSSION... Tonight and Wednesday...Forecast Confidence is medium to high. Sct showers and tstorms will occur this afternoon with SBCAPE's of 1500-2000 J/kg and no capping. Isold to sct showers and storms will probably continue through the evening and overnight via moisture transport, but the more widespread showers and storms will occur on Wed. 1002 mb low pressure area over ern KS will track to north central WI and gradually deepen to 997 mb by 00Z Thu. The strong upper wave lifting nwd from the srn Rockies to MN will continue the deepening Wed nt across Ontario, Canada. A strong cold front will sweep ewd across srn WI late Wed aft- early eve. PWs will increase to 1.8 inches tnt and remain high on Wed until fropa. South to north bands of showers and embedded tstorms will train some, but ewd movement will increase through the day. Thus will not make any changes to the Flood Watch which is in effect for Sauk, Iowa, and Lafayette Counties. Wednesday night and Thursday - Confidence...Medium to High Main story will be the arrival of the coldest airmass of the season. Strong low pressure will shift to the northeast of Lake Superior this period. A cold front will be whipping to the east of the area with 850/925 temps crashing. Left a small pop in the evening for potential for some lingering showers. Otherwise a blustery period with most areas likely not exceeding the 50 degree mark on Thursday. And there will be the return of the wind chill as well. So will be quite an abrupt change from the warm/humid airmass from the days prior. Thursday night through Saturday - Confidence...Low to Medium This will be a cold period as the low level thermal trough is sustained. The 12z ECMWF develops a system and brings precip through the area Friday/Friday night. Meanwhile the GFS and GEM show this system staying further south of the area. A light wind regime and cold airmass could lead to the development of frost for Thursday night in south central WI where it looks like a better shot of some decoupling with the closer proximity to the incoming ridge axis. And then the potential would expand to area wide Friday night. If the ECMWF system were to pan out the clouds and precip would would put the frost idea on the back burner. So for now will steer more towards the frost idea panning out. Some WAA sets up on Saturday between the departed high and ahead of an approaching trough. Saturday night through Sunday night - Confidence...Low to Medium The trough/cold front moves through saturday night or Sunday morning. By and large this fropa looks uneventful but some rain showers do look possible. The 00z ECMWF had then developed a potent low to our southeast with widespread rain and/or snow Sunday night/Monday. The 12z run has backed off with a more southern/weaker look. The 12z GEM stands as the strongest solution with the highest qpf. So the GFS and ECMWF are now more or less glancing shots of rain. 850 temps/1000-500 millibar thicknesses look pretty chilly so some flakes wouldn't be out of the question. Monday and Tuesday - Confidence...Medium Surface/850 ridging takes hold then shifts to the east on Tuesday. Another trough will bring the chance of showers to the forecast later Tuesday or Tuesday evening. AVIATION(21Z TAFS)...Cigs of 3.5 kft this afternoon into the evening along with sct showers and storms. Cigs will then fall to 600-1900 feet from west to east across srn WI from early Wed through late morning. The Cigs may improve to 1-3 kft during the afternoon. Vsbys will be reduced at times tnt-Wed with the rain and possibly light fog. MARINE...A Small Craft Advisory is in effect from 12z Wed to 02z Thu from Port Washington to Sheboygan due to high waves from a persistent sly flow. Afterward, a Gale Watch is in effect from 02z Thu until 17Z Thu for the entire open lakes of Lake MI and the nearshore area from Sheboygan south to Winthrop Harbor, IL. A strong cold front will sweep ewd across the lake Wed evening with wswly gale force gusts possible. The winds will gradually weaken Thu aft-eve. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...Flood Watch through Wednesday afternoon for WIZ056-062-067. LM...Gale Watch from Wednesday evening through Thursday morning for LMZ643>646-669-671-673-675. Small Craft Advisory from 7 AM to 9 PM CDT Wednesday for LMZ643. && $$ Update...Davis Tonight/Wednesday and Aviation/Marine...Gehring Wednesday Night through Tuesday...Collar