Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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140 FXUS63 KARX 191946 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 246 PM CDT Wed Jun 19 2024 .KEY MESSAGES... - Cooler through Thursday with scattered showers/storms, but organized severe weather/heavy rain threats are unlikely. - Increasing risk of heavy rain from multiple rounds of showers/storms Friday/Saturday, with the axis of highest amounts favoring areas north of I-90. Stronger storms are also possible, but confidence is low. - Periodic shower/storm chances are expected next week. && .DISCUSSION... Issued at 245 PM CDT Wed Jun 19 2024 This Evening-Thursday: Cooler, areas of showers/storms A drier, cooler airmass has advected into the area with widespread clouds and scattered showers so far today. Deeper moisture persists into southwest Wisconsin and northeast Iowa closer to the surface boundary. This will be the focus for scattered showers into tonight with modest moisture transport along the front. Any thunder threat will be mostly confined to far northeast Iowa/southwest Wisconsin near/south of the slowly southward- moving boundary. The region looks to remain north of the boundary on Thursday with perhaps modest destabilization occurring across northeast Iowa/southwest Wisconsin. Broad warm advection within southwest flow could result in scattered showers/isolated storms, but overall, with the limited instability, widespread heavier rains are not likely. The severe storm risk also looks low, especially if the boundary remains south of the area. Friday-Saturday: Unsettled, heavy rain possible Will have to keep a close eye on this time period as a surface warm front tries to lift northward ahead of a stronger trough ejects eastward along the US/Canadian border. Eventually a cold front will swing through late Saturday/Saturday night as the wave passes east. Multiple waves of showers and storms will be possible Friday/Saturday within southwest flow and periods of stronger warm advection/moisture transport. NAEFS precipitable water values increase to above the 99th percentile relative to climo late Friday/Saturday with increasing instability and deep warm cloud layers. This environment would be very favorable for heavier rain amounts. Global ensembles already indicate 60-90% probabilities for at least 2" of rain north of I-90 and 20-40% probabilities for at least 3" through Saturday night, and the convective nature of the rainfall would suggest potential for corridors of higher amounts locally. Although mesoscale factors/boundary placement will impact the area of favored higher rain amounts, the highest chances right now are within the region that has seen the higher rain amounts through the week, so flood concerns could ramp up if these trends hold. Some strong/severe storms could occur in this regime as well, especially as the stronger trough approaches, but confidence is quite low in how the environment evolves. Sunday-Wednesday: The pesky front draped near the area may finally be pushed south and east Sunday into Monday as Canadian high pressure builds over the area within northwest flow aloft. Some showers are possible Sunday, though, as a shortwave trough swings southeast. Otherwise, a tendency towards a fairly active zonal flow pattern is expected through the coming work week with lower predictability rain/storm chances and temps near to above average favored. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 1251 PM CDT Wed Jun 19 2024 MVFR cigs and showers will be the main TAF concerns through 18z Thursday. Currently, MVFR bkn to ovc cigs can be noted across much of the local area with coverage slowly beginning to transition more to sct as some subtle dry air aloft works its way in. This is starting to be noted at KRST where increasing wind gusts indicating diurnal mixing has led to a decrease in low-level sky cover. This trend is expected to continue over the next few hours with sky cover clearing. VFR conditions will then persist into the evening and overnight hours with MVFR cigs and shower potential returning by the morning hours on Thursday. Winds will remain fairly light through much of the period at around 5-10 kts. && .HYDROLOGY... Issued at 400 AM CDT Wed Jun 19 2024 There will be a break from the heavy rain through Thursday, but another round of heavy rainfall (2-5 inches) looms for Friday and Saturday across central Minnesota into central Wisconsin. This heavy rain across already saturated soils will result in continued rises along the Mississippi and any tributaries affected by this heavy rain. Many locations along the Mississippi River will approach flood stage towards next weekend (50-70% chance) if rainfall unfolds as forecast. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JM AVIATION...Naylor HYDROLOGY...Skow