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Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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312 FXUS63 KARX 100359 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1059 PM CDT Fri Aug 9 2024 .KEY MESSAGES... - Daytime cumulus and showers/sprinkles continue through today. - Cooler pattern on tap through the next few days. - Low precipitation chances Sunday night into Monday along our southwest. Subsequent precipitation chances from Wednesday into next weekend. && .DISCUSSION... Issued at 106 PM CDT Fri Aug 9 2024 Today: Upper level low on GOES water vapor imagery shows the continually churning upper level low over the Great Lakes early this afternoon, placing the Upper Mississippi River Valley in the upstream Cold Air Advection (CAA) regime. The resultant steepened low level lapse rates have quickened winds near 20 knots in spots and provided a widespread cumulus deck with sprinkles/showers. Temperatures Tonight & This Weekend: With loss of diurnal heating and weakening CAA, expect clearing skies tonight to provide surface temperatures cooling into the mid 40s to low 50s. Increased winds from a tightening pressure/height gradient will keep overnight valley fog concerns at bay while potentially keeping temperatures slightly warmer from increased low level mixing. Therefore, haven`t dropped temperatures in typical cold spots as much, only a couple of degrees. A passing surface high to our south through the weekend will attempt to usher in return flow and warmer temperatures, but will remain shunted by the lingering upper level low and northwest flow. Regardless, slightly more diurnal heating influence will bring temperatures above 70 area wide for the weekend. A persistent pattern expected for the new week as a lifting Central Plains low ushers in weak warm air advection through Monday, keeping temperatures in the 70s to low 80s through the work week. Precipitation Chances Through The Week: Initial precipitation chances reach the local forecast Sunday night into Monday on the cusp of weakening low and accompanying warm sector lifting east northeast through the Central Plains. The local dry airmass with displaced synoptic forcing limit confidence and higher chances to our southwestern peripheral counties in northeast Iowa. Subsequent precipitation chances frequent midweek as long term global ensemble confidence suggests a low bifurcating the long wave ridge. There is some difficulty resolving the behavior of the low potentially rejoining the parent trough over the Upper Mississippi River Valley though so model spread is quite vast with 20-90% for greater than 0.01" in 24 hours. Have kept with National Blend which has 20-50% into the weekend. Will be subsequent details to iron out in coming forecasts. && .AVIATION /06Z TAFS THROUGH 06Z SUNDAY/... Issued at 1058 PM CDT Fri Aug 9 2024 VFR conditions expected through the TAF period. Clearing skies and lighter winds expected overnight. As a seasonably cool airmass remains overhead, boundary layer is not expected to completely decouple, so expecting some winds to remain overnight. On Saturday, expect additional diurnal cumulus to develop as WNW to NW winds remain in the 10 to 20kt range. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JAR AVIATION...JAW