Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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702 FXUS63 KARX 142341 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 641 PM CDT Tue May 14 2024 .KEY MESSAGES... - Maybe some patchy frost in central and north-central Wisconsin tonight. Far too low coverage to warrant a Frost Advisory. - Periodic showers and storms into early next week. Highest rain chances from Wednesday night into Thursday night and from Saturday night into Sunday. && .DISCUSSION... Issued at 158 PM CDT Tue May 14 2024 Tonight and Wednesday 18z WV satellite shows an upper low over MO with latest surface obs and 12z RAOBs showing easterly flow in the low levels. This has largely ushered near-surface smoke from Canadian wildfires to our southwest with no visibility reductions seen today. That said, continued westerly flow aloft has allowed a light distant haze to persist. Given flow pattern and latest guidance, expect the smoke aloft to remain a factor through Wednesday. As sunset approaches Wednesday, some near-surface smoke may return ahead of an approaching trough, but confidence is too low for inclusion in the forecast with this update. Otherwise, expect lows a bit below average tonight given light winds and highs around average for mid- May Wednesday afternoon. Wednesday Night into Thursday Night The 14.12z models are in good agreement that 2 northern stream shortwave troughs will move east through the region. The first moves through the region late Wednesday night and Thursday morning. 0-1 km most unstable CAPES are generally less than 250 J/kg, and 0-3 km and 0-6 km shear remain weak; therefore, not expecting any severe weather. Precipitable water values will climb to around 1 inch. Rainfall amounts will generally range from a 0.25 to 0.50 inch. There is less than a 10 percent chance that the rain will exceed a half inch. A second shortwave trough will move through the region on Thursday evening. There appears that there will be enough clearing in between these systems to allow the 0-1 km most unstable CAPES to climb up 500 J/kg. The highest values are primarily located in the eastern portion of northeast Iowa and in Wisconsin. Like its predecessor, both the 0-3 km and 0-6 km wind shear remains weak, so not expecting any severe weather. However, with an inverted-V in the sub-cloud layer, there will be likely some gusty winds associated with the showers and storms. Wind gusts will be 20 to 25 mph. Rainfall amounts will generally range from a 0.10 to 0.50 inch. There is less than a 10 percent chance that the rain will exceed a half inch. Weekend The models are generally showing zonal (west-east) flow across the northern US. There is a series of weak shortwave troughs embedded in this flow. There continues to be timing issues with these systems. As a result, there will be periodic showers and storms. Overall, the best 0-3 km and 0-6 km shears are closer to the International border and southern Canada, so not any severe weather. Early Next Week The spread in the 500 mb pattern is increasing. While many models are continuing to show zonal flow across the northern US. There are some models suggesting that a 500 mb ridge will develop from the Mid and Upper Mississippi River Valley northeast to Hudson Bay. Due to this uncertainty has been growing, so stayed closer to the NBM when it comes to both temperatures and precipitation. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 639 PM CDT Tue May 14 2024 VFR conditions through this TAF period with increasing mid to high clouds Wednesday afternoon. Winds will be generally light out of the east-northeast tonight, becoming more southeasterly on Wednesday. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Boyne/Ferguson AVIATION...Kurz