Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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757 FXUS63 KARX 281755 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 1255 PM CDT Tue May 28 2024 .KEY MESSAGES... - Rain & Storm Chances Continue Today, Becoming Drier Through Midweek - Below Normal Temperatures Today & Tonight Quickly Warm Back Up Through Wednesday. - Low Confidence In Timing Of Precipitation Chances At The End Of The Week. && .DISCUSSION... Issued at 244 AM CDT Tue May 28 2024 Rain Expectations Today: After a another round of rain and storms through today, a drier forecast is on tap through much of the work week. A phasing negatively tilted trough on GOES Water Vapor imagery over the North Dakota-Minnesota border early this morning is the culprit for these precipitation chances through today. Near mean PWATs of 0.5" to 0.75" in 18.00Z RAOBs with the quick- hitting nature of the wave and best forcing east of the local forecast area will limit overall impacts and rainfall under 0.25", primarily in central Wisconsin. HREF mean, maximum, and probability matched mean are 0.1", 0.5", and <0.1" primarily in central Wisconsin, respectively. Storm Expectations Today: Initial rainfall early this morning remains quite scattered, losing stream quickly before the main show reaches southeast Minnesota near 12Z on the cusp of the surface lows attendant cold front draped to the southwest through the Dakotas early this morning. The cold front and attendant temperature gradient weakens as it approaches the area, decreasing storm extent locally. Although, meager CAA throughout the day will result in persistent scattered precipitation and storms. Steepening lapse rates will result in scattered areas of weak instability near 500 J/kg in spots. Again, higher precipitation chances and subsequent storm chances lie in central Wisconsin and points east. Little to no shear suggests storms pulsing up and down. Irregardless, some could produce small hail from low freezing levels and thick hail growth zones. Cooler Tonight: Higher long term impact from the passing trough will be ushering in a colder, drier Canadian airmass. This colder airmass seen on overnight observations in the Dakotas, antecedent of the cold front, as one would expect. Diurnal timing with the high May sun angle will abate coolest temperatures locally during the day, keeping daytime highs in the mid to upper 60s. As we lose diurnal influence overnight, a drop into the 40s is expected. Warming Through Wednesday: These colder temperatures are short lived however as an amplified upper level ridge with an axis from the Great Salt Lake in northern Utah into central Manitoba early this morning on upper level GOES water vapor imagery traverses through the central U.S. into Wednesday morning. Similar to previous forecasts, long term global deterministic and ensemble models disagree on location of highest heights. Subsequently, Wednesday high temperatures vary from the 60s in the GEFS to 80s in the GEPS. Have blended into the 70s where highest confidence lies. Another impact will be precipitation chances through the end of the work week. Differences in resolving timing of the quasi- omega blocking pattern is to blame. Therefore, with the weakest, quickest ridge, the GEFS returns initial precipitation chances Thursday night.While the GEPS staves off until Friday afternoon into the early evening. Have gone with National Blend for now given the longer forecast window but will be subsequent forecast detail, other than high temperatures through midweek, to keep an eye on. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 1251 PM CDT Tue May 28 2024 Two concerns are present for the upcoming TAF period - thunder in the immediate term and the potential for fog near sunrise. Thunderstorms continue to be rather isolated, so have only elected to cover the ongoing thunder near LSE and have otherwise left thunder out. Users should note that there will continue to be a slight chance (20%) for stray thunder at LSE/RST through sunset this afternoon - confidence and predictability are too low for a mention. As for fog, winds at LSE appear to be a bit too strong for fog to develop at the terminal but will need to keep a close watch on this over the next two cycles. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JAR AVIATION...Ferguson