034 FXUS63 KARX 072244 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 544 PM CDT Fri Oct 7 2022 .DISCUSSION...(This evening through Friday) Issued at 230 PM CDT Fri Oct 7 2022 Key Messages: - Widespread freeze tonight. - Warming up for the first half of next week. - Next widespread risk of showers comes Tuesday into Wednesday. Tonight: Widespread Freeze A modest fetch of stratocumulus with a few areas of light sprinkles/showers (even an mPing ice pellet report NW of Rochester) that extends up into north-central Minnesota is expected to dissipate with the loss of daytime heating this evening. The centroid of a surface high pressure cell slides to the southwest of the forecast area overnight, resulting in winds becoming light and backing to the west/southwest. Despite the winds, temperatures should still fall to or below freezing tonight and bring an end to the growing season for most, if not all of the area. The current freeze warning covers areas that have not seen widespread sub-32 degree readings this fall and if the forecast verifies, it would be the last freeze warning we issue for the season. Saturday - Tuesday: Warming and Dry A downslope-modified airmass over the Dakotas scoots eastward along the northern flank of the departing high pressure cell, with the deeper mixing bringing elevated fire weather conditions in the afternoon for much of the area. See the fire weather discussion for more details. The near-surface flow remains light but mainly from the west to southwest into early next week, promoting a steady warming trend starting through Tuesday--by which point highs will be pushing into the 70s (high confidence given the tight NBM guidance clustering). One compact upper tropospheric wave drops through in the northwest flow on Sunday, but impacts look to be limited to an increase in mid-level clouds or possibly a stray shower. Tuesday Night - Thursday: Showers Followed by Cooler Weather The upstream pattern amplifies as we head into the middle part of the week with a trough digging over the western CONUS. A surge of higher theta-e air races northward by Tuesday afternoon, with the combination of the increasing theta-e advection and isentropic ascent fueling a modest corridor of rainfall tied with the deeper moisture transport max. The guidance solutions differ on the position and amplitude of the wave by this point, resulting in the possibility that the bulk of this first wave of precipitation only clips the southern portion of the forecast area. However, a second round of showers and possibly thunderstorms tied to an advancing cold front sweeps through region Tuesday night into Wednesday . It is too early to hang one's hat on a given solution, but the dynamic nature of this wave does increase the risk of organized thunderstorm activity IF return moisture and instability are sufficient. The extended CSU severe weather guidance paints a narrow ribbon of 5% severe weather probabilities over the area, but this again is of lower confidence. Temperatures steadily fall behind the cold front for the latter part of the week, but how the pattern responds in the wake of this front is poorly resolved and results in a wider spread in the NBM temperature forecasts beyond Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 544 PM CDT Fri Oct 7 2022 VFR conditions are expected through the TAF period with clearing skies this evening. Winds will trend WSW and increase to around 10 kts with gusts to 20 kts Saturday afternoon. && .FIRE WEATHER... Issued at 230 PM CDT Fri Oct 7 2022 Drier air from the Dakota's translates eastward into the region for the day tomorrow. Dewpoints are forecast to fall into the lower 20s by peak heating with a few lower outlier model guidance solutions pushing afternoon dewpoints into the teens. Afternoon humidity values are expected to fall into the 20-30 percent range, though if one of the outlier solutions were to verify we may see RH values closer to 20 percent. Mixing heights of 3-4 kft would tap into westerly winds of 20 kts aloft for potential gusts at the surface. These winds and RH values could result in elevated fire danger concerns, most notably for those working in agriculture fields where fuels are the most cured. The winds taper off in the evening with increasing RH values of 30-40 percent for Sunday. The next chance of rain does not look to arrive until Tuesday or Wednesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Freeze Warning from 1 AM to 8 AM CDT Saturday for WIZ041-043-044- 053>055-061. MN...Freeze Warning from 1 AM to 8 AM CDT Saturday for MNZ086>088- 094>096. IA...Freeze Warning from 1 AM to 8 AM CDT Saturday for IAZ008>011-018- 019-029-030. && $$ DISCUSSION...Skow AVIATION...JM FIRE WEATHER...Skow