Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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384 FXUS63 KARX 061154 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 654 AM CDT Sun Oct 6 2024 .KEY MESSAGES... - Blustery conditions through late this afternoon with northwest winds of 20-25 mph, gusting at times to 30-40 mph, especially this morning. - Today will be the coolest day of the week with highs in the upper 50s to mid 60s. We could see at frost across for much of the region tonight. A steady warming trend ensues during the week with highs again approaching 80 degrees by Friday. - No rain in store for the work week with the next window of opportunity for any rainfall coming next weekend. && .DISCUSSION... Issued at 300 AM CDT Sun Oct 6 2024 Today: Cooler and Blustery An initial cold front swept through the region yesterday evening and resulted in scattered storms north of I-94. A secondary cold front is plowing southeastward out of North Dakota and northwestern Minnesota early this morning and reaches our doorstep towards sunrise. Overnight wind gusts in the wake of this front have peaked between 40-45 kts across central Minnesota; however, these winds are expected to lessen as the surface low lifts further to the northeast into western Ontario, pulling the strongest pressure rises/tightest pressure gradient fields/lowest PV 1.5 surfaces along with it. That being said, the surge of cold air advection has ample momentum when it arrives with boundary layer lapse rates quickly steepening and allowing stronger gusts to penetrate to the surface. Gusts of 30-35 kts are likely between 10-12Z along and north of I-90, with gusts of 25-30 kts spreading southward between 12-14Z. Blustery conditions last for much of the day, though winds decline this afternoon with the pressure gradient relaxing. Temperatures in the 850-700-mb layer will be 15 C cooler than yesterday, with surface temperatures reflecting this airmass change and holding in the upper 50s to low 60s for highs--very close to the AVERAGE highs for this time of year. Tonight: Frost Potential A 1023-mb surface high pressure cell builds into the region for tonight, setting the stage for the first decent frost/freeze of the season outside of the Wisconsin sand bogs, which have had periods of frost for several weeks now. We are running about 1-2 weeks behind our climatological first frost (< 36 F) dates and in fact are passing our typical freeze (< 32 F) dates right now, indicative of how warm our pattern has been over the last month. Did lower tonight`s temperatures closer to the NBM 10th percentile and expand the mention of frost in the forecast given the drier dewpoints and lighter winds, which increases the potential for temperatures to fall even further in low-lying locales. The best potential for a widespread freeze will be north of I-90 in Wisconsin (outside of the Mississippi River Valley) with forecast lows ranging from the mid-20s to low 30s. The only fly in the ointment for this forecast may come in the form of mid to high clouds arriving from the northwest ahead of a subtle upper tropospheric wave, but these look to move in after 09Z timeframe, with much of the radiational cooling having already taken place by then. Tuesday - Saturday: Dry and Warming Split flow/longwave ridging builds across the central and western CONUS and Canada for Tuesday through the end of the week. The mean ridge axis gradually slides east/southeast towards the region through the week, with lower tropospheric temperatures gradually warming during this timeframe. By the end of the week, we should be looking at highs returning to upper 70s to low 80s, near record values for this time of year. It is impressive to see the NBM already depicting near record highs 5-6 days out, which reflects the strength of this anomalous warmth in the various EPS/GEFS ensemble inputs (60-80% of the EPS members are already around record highs per the Extreme Forecast Index). The next shot of precipitation comes over the weekend as the ridge flattens and the next shortwave can finally bust through, but even right now only a handful (10-20%) of the longer range solutions have any measurable precipitation. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 654 AM CDT Sun Oct 6 2024 VFR conditions are expected through the TAF period. Satellite imagery early this morning shows a large area of low VFR stratus dropping down across Minnesota. Based on latest trends, it looks more possible that these clouds make it further south towards the TAF sites for a time this morning. Otherwise, northwest winds are starting to pick up again this morning, with gusts of up to around 25 to 35 kts possible. Winds gradually weakening through the afternoon, eventually becoming light into the overnight hours. && .FIRE WEATHER... Issued at 300 AM CDT Sun Oct 6 2024 There may be a period of elevated fire weather conditions this afternoon with northwesterly winds sustained around 15-20 mph, gusting to 30-35 mph at times. These winds will be on a slow decline as we move through the afternoon as RH values reach their lowest values around 30 to 40 percent (lowest west of the Mississippi River). Build-Up Indices have also slowly crept up over the last few days and are between 80-100 west of the Mississippi River, indicating that vegetation is approaching dryness levels that favor quick fire growth. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Skow AVIATION...EMS FIRE WEATHER...Skow