Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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717 FXUS63 KARX 201035 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 530 AM 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 /12z TAFS THROUGH 12Z SATURDAY/... Issued at 530 AM CDT Fri Sep 20 2024 CIGS: low clouds are quickly exiting east and should clear KLSE by 12-13z. SKC conditions expected for the rest of today into the evening. High/mid level VFR clouds look to return from the west overnight. WX/vsby: with an increase in high level clouds expected overnight, drier air spreading in from the west and limited depth to the light wind layer, the threat for valley fog impacts at KLSE tonight are low (at this time). Will continue to monitor trends and adjust forecast if trends show differently. Rain chances return Saturday, moreso late afternoon/night per latest short term guidance. WINDS: swinging west with the passage of a sfc front early this morning, then light and back to the south/southeast tonight. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Cecava AVIATION.....Rieck