Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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853 FXUS63 KARX 201717 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1217 PM CDT Fri Sep 20 2024 .KEY MESSAGES... - Above normal temperatures continue through Saturday before cooling down to more seasonable temperatures lasting into the middle of next week. - Chances of rain return for Saturday and Sunday as next system moves into the region. && .DISCUSSION... Issued at 249 AM CDT Fri Sep 20 2024 More Storm Chances for the weekend and early next week: A short break in the action as surface high pressure builds in for Friday. Heading into Saturday evening, a low across the US/Canada border moves eastward while a closed low across the Intermountain West pushes northeastward towards the Central Plains. Splitting these two systems is a shortwave that will move through the Upper Midwest Saturday afternoon through Sunday. This will bring the next chance of showers and thunderstorms to the area. Compared to early next week, there seems to be a good agreement on precipitation occurring. As this wave moves through, most of the precipitation will be focused south of our CWA but northeast Iowa and southwest Wisconsin will have the best chance (50 to 70%) for rain to occur. When looking at ensemble guidance, the 25th to 75th percentiles for 24 hour precipitation totals ending Sunday evening are between 0.25 and 0.75" for the GEFS and 0.02 to roughly 0.25" for the EPS. This difference is because the EPS and ECMWF keep the majority of the precipitation to our south. By Monday, the remnants of the closed low move into the area. Current ensemble and deterministic guidance have some differences. The GFS has the low further south than the ECMWF. This is represented in the ensembles with most of the GEFS having fewer precipitation than the EPS through Tuesday. Some members (around 25%) of the EPS do have drier solutions, so there is still uncertainty around the exact trajectory this closed low takes. Depending on the path it takes, will determine how far north the the precipitation goes. With both of these storms, we will continue to monitor to see how precipitation trends go. Warm temperatures through Saturday then cooler for next week: Above normal temperatures (10 to 15 degrees above normal with some locations approaching 20 degrees above normal) across the forecast area with highs in the upper 70s to mid 80s through Saturday. After Saturday, more seasonable temperatures for the beginning of next week. High temperatures are expected to be in the mid 60s to near 70 for Sunday and Monday and then gradually warming up to the low to mid 70s for the middle of next week. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1217 PM CDT Fri Sep 20 2024 VFR conditions are generally expected through the TAF period with high-level clouds moving in during the overnight hours. Winds will remain between 5-10 kts this afternoon before becoming light and shifting to south/southeasterly this evening. Low-end potential for valley fog at KLSE exists with the lighter surface winds. However, with some high-level clouds and stronger winds off the deck in model soundings (HRRR/RAP/NAM) this potential remains low (10% chance). With some warm air advection moving in during the morning hours, would not be able to rule out an isolated sprinkle/shower before more significant precipitation moves in after 18z. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Cecava AVIATION...Naylor