Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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208 FXUS63 KARX 170337 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1037 PM CDT Thu May 16 2024 .KEY MESSAGES... - While a couple thunderstorms may develop in the far eastern portions of southwestern and west central Wisconsin this afternoon, this threat is expected to end over the next couple hours with severe thunderstorms no longer expected. - A chance (20-30%) for thunderstorms returns Saturday afternoon and evening. If thunderstorms develop, a stray severe thunderstorm cannot be ruled out. - Next week features repeat chances for showers and thunderstorms. Currently, confidence in timing is low, so these chances are spread over many more periods than will ultimately be affected. Additional refinements will occur in the coming days. && .DISCUSSION... Issued at 437 AM CDT Thu May 16 2024 This afternoon: 19z WV satellite shows a weak shortwave over Black River Falls with visible and IR channels showing a field of cumulus largely with little vertical extent, with the exception of couple small storms around Baraboo/Madison. This largely comports with non-NAM guidance, which suggests warm temperatures around 750mb are preventing deep convection from developing and will continue to do so this afternoon. As the aforementioned shortwave exits to the east in the next couple hours, the chance for additional rain will end. Saturday thunderstorms: Saturday, upper low looks to advance from North Dakota to Montana with an associated weak surface front progged to sweep eastward through Minnesota with a narrow axis of moisture advecting northeastward ahead of this feature. Model guidance suggests around 1000 J/kg of MLCAPE could build by late afternoon. As the front arrives, a few showers and thunderstorms could develop, particularly if the front arrives before surface heating is lost. While best upper level winds and thus deep shear remain displaced well to our north and west, if thunderstorms do develop, some severe hail could occur given aforementioned instability and 700-500mb lapse rates favored to be around 7.5 C/km. Sunday night through Thursday precip: Next week brings an extended period with west-southwesterly to southwesterly flow aloft. Guidance depicts a variety of shortwaves ejecting downstream in this flow with a variety of exact timings. Thus, while NBM PoPs were allowed to remain in the forecast, expect the periods with likely showers and thunderstorms to eventually focus on shorter time periods once details become clearer. && .AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1037 PM CDT Thu May 16 2024 Weak surface ridge builds into eastern Minnesota/western Wisconsin tonight into Friday. Subsidence underneath ridge will allow for mostly clear skies tonight into Friday morning. Some mid to high clouds are expected to drift over the area Friday afternoon/evening. However...ceilings should remain VFR through the taf period at both RST/LSE taf sites. Pressure gradient tightens on backside of surface ridge Friday afternoon/evening. Wind speeds will be 10 to 15 knots with gust to around 20 knots by 18z Friday especially west of the Mississippi River. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Ferguson AVIATION...DTJ