Area Forecast Discussion
Issued by NWS Green Bay, WI
Issued by NWS Green Bay, WI
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198 FXUS63 KGRB 021804 AFDGRB Area Forecast Discussion National Weather Service Green Bay WI 104 PM CDT Tue Jul 2 2024 Updated aviation portion for 18Z TAF issuance .KEY MESSAGES... - Periods of rain may be heavy at times through late tonight. In general, 0.5 to 1.5 inches of rain is expected across the entire area, highest in central Wisconsin, which could lead to minor river and stream flooding, along with urban flooding. - Conditions will be hazardous to mariners and beachgoers on the bay and Lake Michigan through tonight due to gusty winds and high waves. - The next round of widespread rain arrives late on the 4th of July and will last through Friday. && .DISCUSSION... Issued at 358 AM CDT Tue Jul 2 2024 Rounds of showers and some thunderstorms expected through tonight. Moderate to heavy rainfall is likely, especially over central WI. It then turns mainly dry Wednesday and Wednesday night, before more showers return later on the 4th, continuing through Friday. First full weekend of July will be unsettled with chances for showers and thunder both days. Today...Showers with moderate to heavy rain ahead of a shortwave trough and well to the north of main warm front are shifting across the state early this morning. Decaying area of lightning strikes is present over southwest cwa on edge of MUCAPE of 1-2k/kg well to the west and southwest over IA. As shortwave and low- level jet translate east this morning, expect widespread showers early to be followed by additional showers through midday. Maybe a brief lull after that over parts of the area, but there will already be another sharp H7 shortwave (generating showers and storms over west central IA at current) and resurgent low-level jet taking aim into central WI as early as early to mid afternoon. This should keep at least scattered showers going. As has been highlighted, PWATS nearing 2 inches are well above the 90th percentile and closer to max values for early July. Thus the threat for heavy rain will be across the region all day. With multiple rounds of showers at the worst and patchy drizzle and cloud cover at the best, went lower for high temps today. 70 will be a stretch for any spot in the cwa today and northwoods will have tough time reaching mid 60s. Tonight into Wednesday...Another round of moderate to heavy rain likely as primary shortwave trough edges closer and stronger shortwave within the trough rotates through. Right entrance jet forcing will only enhance lift as warm front approaches. Sfc based instability (and associated severe threat) will be maximized along and south of the warm front and approaching low pressure wave, but sufficient MUCAPE just upstream of our area along with PWATs still around 2 inches suggest moderate to heavy rain showers especially during the evening into the early overnight hours scntral to east-central WI along increasing low- level jet. To the west of the LLJ axis, appears showers shut down quickly after midnight especially after weak cold front/drier air moves through. All areas should be in the process of drying out by daybreak as the boundary shifts east of WI. Most areas will be dry rest of Wednesday, but a few isolated showers out of some high based stratocu may fall across northern WI. Rebound day for temps with readings pushing into the 80s. Soundings and MOS guidance point to it turning breezy from the west (gusts 25-30 mph) midday into the afternoon. 4th of July and Friday...Signals in models and ensemble guidance remain persistent that as shortwave trough digs across the northern Plains and sfc low spins up over the upper mississippi river valley by Friday morning, showers will spread west to east across WI late Thursday afternoon into Thursday night. Heavier rain likely holds off til late Thursday night into Friday, but sufficient forcing ahead of the trough and some elevated MUCAPE justify pops increasing to likely for central WI Thursday evening while there is still a bit of uncertainty on whether the more widespread showers reach the Fox Valley and lakeshore areas by late evening or more so overnight. Looking like widespread showers are in store for Friday (possible heavy rain again) and with sfc low tracking across or south of our area, it likely will be another cooler early July day with highs probably ending up below normal. Sat-Mon...Pattern remains active with multiple shortwave troughs and frontal boundaries dropping across the region. There will be a lot of dry time, but the forecast carries chances of showers throughout. At this time, Sunday looks like the day with better chance of more widespread showers. Temps will be at or slightly below normal. && .AVIATION...for 18Z TAF Issuance Issued at 103 PM CDT Tue Jul 2 2024 Look for MVFR/IFR ceilings to prevail for the rest of the afternoon into early Wednesday morning. The exception will be some VFR conditions across east-central WI this afternoon. Some LIFR ceilings are possible overnight into early Wednesday, especially across central and north-central WI. A lull in the widespread shower activity is currently moving through, but expect another large area to arrive later this afternoon and evening, impacting east-central WI. Shower coverage will decrease as you head toward RHI. Have not included thunder chances yet as there is still some uncertainty on when any elevated storms will impact a specific site, but TEMPO groups may be needed eventually. Flying conditions look to improve Wednesday morning, mainly after sunrise. Gusty south winds are expected to continue this afternoon, then gusts will diminish toward/after sunset. Winds will shift to the west early Wednesday and become gusty by mid-morning. Low-end LLWS will be possible tonight, especially over eastern WI. && .GRB WATCHES/WARNINGS/ADVISORIES... Beach Hazards Statement through Wednesday morning for WIZ022-040- 050. && $$ DISCUSSION.....JLA AVIATION.......Bersch