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Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
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627 FXUS63 KARX 101133 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 633 AM CDT Sat Aug 10 2024 .KEY MESSAGES... - Seasonably cool temps will continue through the weekend with gradually warming expected heading into next week. - Little rainfall potential through the weekend, with shower/storm chances increasing at times next week, but confidence in details (timing, impacts...) is low for now. && .DISCUSSION... Issued at 257 AM CDT Sat Aug 10 2024 This Weekend: Dry, cool Seasonably cool, tranquil weather will be the rule through the weekend. A few weak ripples in the flow will slide southeast on the periphery of the closed upper low over Ontario that will slowly move east through the weekend. However, with some warming of mid-level temps today and minimal instability, the risk for any showers is much less than Friday, although a diurnal cumulus field likely will develop as boundary layer warming occurs beneath seasonably cool air aloft. Low level thermal profiles will slowly moderate through the weekend as the flow trends more zonal and the upper low across Canada pulls east. As a result, highs today in the mid 60s to mid 70s will increase into the 70s to near 80 on Sunday with lows tonight mainly in the 50s, except for typically cooler locales which could fall into the mid 40s. Monday-Friday: Increasing shower/storm chances, warming Overall, modest mid-level height rises are expected heading through the week as broad ridging tries to work eastward from the Rockies/plains. This generally supports a return to milder, more seasonable temps through the week. However, global model guidance indicates a series of embedded shortwave troughs within the fairly zonal flow regime that could not only impact rain chances and clouds, but also daily temps. One such wave is forecast to pass east from the northern plains to the Upper Mississippi Valley Sunday night into Monday. However, with modest forcing and a drier airmass locally, organized rain chances should dwindle with eastward/northward extent. Right now low to medium (20-40%) chances are focused south of I-90 Sunday night into Monday (highest over northeast Iowa). Either way, instability looks quite limited with this system as the low level jet/deeper moisture remain off to the south and west. Moisture return should increase through the mid/latter portion of the week as low-level flow becomes southerly amid the ridging spreading east aloft. An uptick in shower/storm chances is expected in conjunction with the moisture increase, although predictability in details of the pattern evolution, especially with the timing and amplitude of shortwaves, lowers with time. Accordingly, stuck close to the broad-brushed blended (NBM) rain chances (20-40%) through the mid to late week period. Overall, it does look to be a more active period, though, and higher rain chances will likely be needed in time for some of these periods as forecast confidence increases. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 633 AM CDT Sat Aug 10 2024 VFR conditions are expected through the TAF period with sct to bkn cumulus expected during the afternoon. Winds will increase during the afternoon to around 10-15 kts with diurnal mixing aiding increasing wind gusts of up to around 20 kts. Winds will diminish closer to sunset to around 5 kts. As we head into the overnight, skies clear and winds lessen however, with the 10.09z RAP showing fairly strong winds off the deck to around 15-20 kts, valley fog formation at KLSE appears unlikely at this time. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...JM AVIATION...Naylor