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Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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265 FXUS63 KARX 161933 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 233 PM CDT Fri Aug 16 2024 .KEY MESSAGES... - Showers and isolated storms continue for the rest of this afternoon and into the evening hours. Additional chances (20-40%) for showers persist for Saturday afternoon. - Temperatures through next week will likely trend near to slightly below average for this time of year with relatively minimal precipitation chances. && .DISCUSSION... Issued at 233 PM CDT Fri Aug 16 2024 Today - Saturday: Seasonably Mild with Showers and Isolated Storms The overall synoptic setup this afternoon revolves around a vertically stacked upper-level to surface low centered across north- central Wisconsin. Pivoting around this feature are several subtle shortwaves aiding in instigating showers and storms with the overall mesoscale environment featuring two distinct modes across the local area this afternoon. Where low-level moisture has maintained with dewpoints in the upper 60s to around 70, MUCAPE values remain elevated enough (1000-2000 J/kg) to support more vigorous convection as seen late this morning in Clark and Jackson counties. West of the Mississippi River, increasing cloud cover and lower dewpoints have minimized the amount of instability present. Consequently, would expect the predominant mode of precipitation to be showers with a low-end chance for a rumble of thunder or two west of the Mississippi River. The potential for funnels throughout the afternoon generally has trended less likely with guidance lacking a surface feature to really latch onto as a subtle boundary pushes east of the local area. As a result, have noted fairly low values in the non-supercell tornado parameter in the 16.15z RAP for the local area. Regardless, as cloud cover pushes east with the cyclonic flow, instability will begin to wane favoring a more showery environment into the evening hours for much of the local area with showers gradually dispersing by sunset. As we head into Saturday, the upper-level low continues to push southeast through the Great Lakes. With a more northwesterly flow regime and cloud cover overhead, temperatures will trend on the milder side with highs in the middle to upper 70s across the region. With additional weak pieces of upper-level energy behind the upper- low, much of the CAMs still paint some shower coverage for the afternoon on Saturday. A rumble of thunder or two cannot be ruled out with MLCAPE values of up to around 500 J/kg in the 16.15z RAP. Similar trend for Saturday as today with showers waning in coverage later into the evening hours as well. Sunday - Friday: Continued Slightly Below Average Temperatures Looking into next week, our region is situated between two broad synoptic features with a large upper-level ridge to the west and a trough to the east. Consequently, our region is once again stuck in northwesterly flow which will aid in keep our temperatures slightly below normal through next week with median high temperatures of middle 70s to lower 80s in the 16.00z grand ensemble (GEFS/EC ens/Canadian ens) with little inter-quartile spread amongst ensemble members. Precipitation chances appear minimal into next week with any shortwaves riding over the aforementioned ridge being the main source of any precipitation potential which long- range guidance currently does not reflect. Regardless, with the 16.00z grand ensemble (GEFS/EC ens/Canadian ens) having very low joint CAPE (over 500 J/kg) and shear (over 30 kts) probabilities of under 20% through the middle of the week, any organized severe weather appears unlikely at this time. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 1235 PM CDT Fri Aug 16 2024 Numerous showers move through the region early this afternoon, becoming more isolated towards the late afternoon with the risk for isolated showers continuing into Saturday. The threat for thunder with these showers is very low and not mentioned in the TAFs. Periods of MVFR to IFR visibilities are possible under any of the heavier showers. Widespread MVFR to IFR ceilings move in this afternoon and persist into Saturday with the lowest ceilings overnight along with lower visibilities due to fog. Winds veer from the WSW to the NW today around 10 kts, gusting to around 20 kts this afternoon west of the Mississippi River. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Naylor AVIATION...Skow