946 FXUS63 KARX 050758 AFDARXArea Forecast Discussion National Weather Service La Crosse WI 258 AM CDT Fri Sep 5 2025
.KEY MESSAGES...
- Isolated showers (20%) possible today and into Saturday. Otherwise mainly dry weather through the weekend.
- Unseasonably cool temperatures through this weekend. Some locations may reach record cold high temperatures today with highs of 52-62 degrees.
- Temperatures begin to warm next week, with highs in the 70s returning by the middle of the week.
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.DISCUSSION... Issued at 258 AM CDT Fri Sep 5 2025
Today through Sunday night
Latest water vapor satellite imagery shows upper level trough digging over southern Ontario Canada/Great Lakes region. First impulse and associated shower activity has pushed of the forecast area per latest mosaic radar. Upper level trough will continue to dig over southern Ontario Canada/Upper Great Lakes Region through the weekend. A couple of shortwave troughs will rotate around the upper level trough and into the forecast area today into Saturday. With daytime heating and lift associated with the first shortwave trough today. However with moisture limited...expect isolated showers to develop this afternoon/evening. Have introduce isolated showers this afternoon/evening with higher probability of showers northern portions of the forecast area where the deeper moisture is located.
Another shortwave embedded in the northerly flow aloft tracks over the forecast area Saturday. Isolated showers will once again be possible across the forecast area mainly Saturday afternoon/evening. At this time will let later shifts to introduce small chances of showers.
With the northerly flow aloft...colder airmass will advect into the forecast area over the weekend. The 05.00z deterministic models suggest 850mb temperatures to be plus 1 to plus 3 degrees celsius through 00z Monday. Latest NAEFS indicate standard anomalies of minus 2 to minus 4. Temperatures through the weekend will be well below normal. High temperatures are expected to be mainly in the 50s to lower 60s today and Saturday and slightly warmer in the upper 50s to middle 60s Sunday.
Monday through Thursday
Main forecast concerns are shower chances Monday night into Tuesday night...then temperatures warming. Another shortwave trough embedded in the northwesterly flow aloft moves across the Upper Great Lakes Region Monday night into Tuesday night. Vertical motion and moisture convergence along the surface front will allow for development of showers and possibly storm or two across the forecast area. With the surface slowly moving east/southeast over the southern forecast area Tuesday evening/night will chance of showers or a couple of storms into the Tuesday night. Then...upper level trough over the northeast United States breaks down and upper level ridge builds into the central United States Wednesday into Thursday. The latest ensembles and deterministic models have differences on how amplified the upper level ridge will be. However...temperatures are expected to warm back to near or slightly below normal by middle of next week.
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.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/... Issued at 1224 AM CDT Fri Sep 5 2025
MVFR ceilings are spreading southward into RST and LSE early this morning and will persist through roughly 14-16Z. There may be temporary scattering or jumping to VFR, however. Otherwise brisk northwest winds will continue to gust to around 30 knots through around daybreak, with lower gusts around 20-25 knots expected during the day. Winds will diminish at sunset. Very small (
NWS ARX Office Area Forecast Discussion