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Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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939 FXUS63 KARX 301633 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1130 AM CDT Sun Jun 30 2024 .KEY MESSAGES... - Two rounds of convection are expected Monday night into Tuesday, likely bringing a threat for heavy rain. Some severe storms could occur Tuesday afternoon and evening. - Additional rainfall could occur Thursday through Saturday but, at this time, heavy rain chances appear to be lower during this period. && .DISCUSSION... Issued at 409 AM CDT Sun Jun 30 2024 * MONDAY NIGHT INTO TUESDAY: Heavy Rain Threat, Potential Severe Monday, as a surface high, currently located over MN, continues to shift eastward after bringing us pleasant weather today, next upper trough advances over the central/northern Rockies and Canadian Prairies. Expect 850mb moist fetch from the Gulf of Mexico to resume in earnest as a result. With plenty of moisture returning to the CWA, widespread convection should occur, with guidance in pretty good agreement considering the day 2-3 lead time that this will mainly focus on two rounds: the first with a lead shortwave Monday night into Tuesday morning and the second Tuesday late afternoon into the late evening as the main body of the upper trough approaches. That said, with various shortwaves likely to eject downstream in the interim, lingering convection could occur through the day Tuesday. Little change from the past few forecast updates - the primary threat during this period will be heavy rain. Both NAEFS and ENS PWATs continue to approach the 99.5 percentile of their respective model climatologies in their latest cycles. NBM probabilities indicate most areas will receive around 0.75" to 2" of rain from Monday night through Tuesday night with the potential for localized areas to approach 4", in line with the convective nature of this event. Given the high amount of antecedent rainfall, flash flooding and additional river flooding will be concerns. As for severe thunderstorm potential, the convergence across guidance toward two primary rounds of convection with the second beginning late Tuesday afternoon as peak heating occurs suggests vigilance will continue to be needed. However, while shear profiles are broadly supportive of an all-hazards severe risk day, convective debris from Tuesday morning`s convection still appears more likely than not to prevent sufficient destabilization for that threat to be realized in our CWA. * THURSDAY THRU SATURDAY: Additional Chances for Rain Thursday into Saturday, guidance shows increasing agreement that an upper low will bring potential for additional rainfall. Best moisture transport is still largely displaced to our south, with GEFS/ENS PWAT percentiles below the 90th during this period. Thus, while additional rain is unwelcome, a repeat of the widespread threat for flash flooding and rises in the non-Mississippi basins expected Monday/Tuesday does not appear to be in the cards for later in the week. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1130 AM CDT Sun Jun 30 2024 CIGS: SKC through the overnight with a band of sct-bkn mid level VFR clouds for Mon morning. Look for further increase and lowering of the deck as Monday wears on, likely dropping into MVFR overnight, associated with rain. WX/vsby: despite high pressure building overhead and light decoupled winds at KLSE, near sfc moisture looks too dry while there could also be an uptick in winds just off the sfc overnight, thus not expecting any river valley fog to impact KLSE Mon morning. Rain returns Monday night with vsby restrictions expected. WINDS: north/northeast becoming light southeast tonight. Winds increasing Mon morning, gusting into the mid 20s then into Mon evening. && .HYDROLOGY... Issued at 217 PM CDT Sat Jun 29 2024 Minor to moderate flooding continues along the Mississippi River and will continue into next week. Additional rainfall is expected Monday night into Tuesday evening. Rainfall amounts of 1 to 3 inches is possible across the area during this time. River flooding and flash flooding is possible due to antecedent conditions across the area. Interests along rivers and creeks should monitor the latest forecast and trends Monday night into Tuesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Ferguson AVIATION.....Rieck HYDROLOGY...DTJ