Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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434 FXUS63 KARX 200414 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1114 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 /06Z TAFS THROUGH 06Z FRIDAY/... Issued at 1055 PM CDT Wed Jun 19 2024 VFR ceilings fl100 tonight deteriorating Thursday to MVFR with scattered showers and a few thunderstorms. The latest surface analysis had surface high pressure over the TAF sites with dewpoints in the 50s and the 60s dewpoints off to the south and the surface front over parts of IL. The showers tonight are generally expected to remain to the south tonight, however after 09Z we see the 925mb flow becoming more southerly with increasing moist low level flow returning. This should favor showers re-developing. Included VCSH after 14 or 15Z at the TAF sites with ceilings becoming MVFR 16-18Z. The short term models are on the dry side at the TAF sites, but scattered showers seem reasonable for Thursday. Thunder will also be possible, however due to low confidence on timing did not include at this time. && .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...Zapotocny HYDROLOGY...Skow