Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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602 FXUS63 KARX 172337 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 637 PM CDT Fri May 17 2024 .KEY MESSAGES... - Saturday afternoon and early evening brings potential for showers and thunderstorms to mainly west central Wisconsin. If thunderstorms do develop, a severe storm cannot be ruled out. - While it remains difficult to narrow down timing, next week looks to feature multiple rounds of showers and thunderstorms. Additionally, next Tuesday may feature the ingredients for severe thunderstorms but these are currently favored to develop south of the forecast area. Please keep up to the date with the forecast for next week. && .DISCUSSION... Issued at 425 AM CDT Fri May 17 2024 Saturday thunderstorms: A shortwave looks to eject northeastward over ND to western Ontario. An associated cold front will sweep eastward through MN toward the CWA. Plume of moist advection ahead of this front should lead to an axis of around 1000 J/kg of MLCAPE by the afternoon hours. As the front arrives, a few showers and thunderstorms may develop. Model soundings suggest warm temperatures at 750mb will likely limit the ability for deep convection to develop, especially in southern parts of the CWA. Additionally, with better winds aloft remaining to our north, deep shear of only around 20 knots suggests convective organization will be lacking. Thus, severe risk appears limited to a stray severe hail or wind event. Sunday night through Friday precip: Next week brings an extended period with west-southwesterly to southwesterly flow aloft with a series of shortwaves embedded in this flow. With good 700/850mb moist advection seen ahead this waves, multiple rounds of showers and thunderstorms will occur. PoPs are once again spread across a much larger time period than will be affecting, owing to low predictability in the timing of the aforementioned shortwaves. Of particular note is Tuesday, which looks to feature a rather potent shortwave with most guidance bringing this northeastward during the afternoon and evening hours. Ahead of this feature, moist advection tracing back to the Gulf of Mexico could lead to large amount of instability. With stronger winds aloft favored, this could lead to a risk for severe thunderstorms. Primary uncertainties surround the exact track of the system - if the system tracks just a bit too far to the south, the forecast area would fail to destabilize owing to ongoing rain during the morning hours. As of this time, LREF joint probabilities suggest the best overlap of shear, potential instability, and low convective inhibition is more probable just to our south, but will need to keep a close eye on this over the coming days. && .AVIATION /00Z TAFS THROUGH 00Z SUNDAY/... Issued at 637 PM CDT Fri May 17 2024 VFR conditions are expected through much of the TAF period with intermittent middle to high level clouds. Winds will decrease overnight marginally as diurnal mixing subsides. Ahead of an incoming frontal boundary, winds will increase again from the south on Saturday to around 15-20 kts with gusts of up to 30 kts. As the front approaches, available low-level moisture will allow for some shower/storm activity to get going during the afternoon. However, questions remain on how vigorous any convection will get as short-range model guidance varies considerably. As a result, opted to hold with a VCSH at both TAF sites for now. Winds will shift to west/northwest behind the frontal passage and begin to diminish going into Saturday evening. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Ferguson AVIATION...Naylor