


Area Forecast Discussion
Issued by NWS La Crosse, WI
Issued by NWS La Crosse, WI
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
066 FXUS63 KARX 012329 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 629 PM CDT Tue Jul 1 2025 .KEY MESSAGES... - Smattering of storm chances Wed-Thu. A few stronger storms but the threat for organized severe weather currently looks low. - Steamy start to the holiday weekend with heat indices topping out in the mid to upper 90s for the 4th. Cooler end with Sunday highs in the upper 70s/lower 80s. - Highest rain threat overnight Fri into Sat. Smaller chances for storms Fri afternoon, but more uncertain. && .DISCUSSION... Issued at 100 PM CDT Tue Jul 1 2025 > WED-THU: Scattered storm chances. A few strong storms possible. Convection expected to spark over the northern plains later tonight, in response to ripples in the 500 mb flow along with nose of the 850 mb jet/moisture transport. These shower/storm clusters should experience a decrease in coverage/intensity as they move southeast Wed morning. However, these now convectively enhanced bits of upper level energy will stay intact, spinning across the local area for the afternoon/early evening. The summery airmass paints 1500-2500 J/kg of SBCAPE for the afternoon with much/if not all low level capping eroding by mid afternoon. Roughly 35-40 kts of 0-6km shear via the NAM/GFS could/would add support to convective updrafts and sustainability-development. Enough there for a stronger storm potential. More uncertainty on if there would be a severe risk. It`s not clear where the upper level features will be by the afternoon, and potentially any related sfc/outflow boundaries. Expectation is for storms to pop in relation to the upper level forcing and increasing instability, tracking southeast across parts of the area. CAMS don`t indicate much areal coverage at this time. The low level jet looks to reassert itself into northwest IA Wed night, with another cluster of convection firing there - moving southeast during the night. For Thursday, a warm front is likely to be wavering across central MN into central WI with more bits of convectively enhanced shortwave energy dropping over the plains ridge. More scattered convection should spark. Deterministic runs of the GFS/NAM/EC keep most of this along/north of the warm front - roughly north of I-90. Again, fair amount of uncertainty as various small scale interactions will impact where storms develop/move. Also, not a lot of areal coverage in the QPF footprint. Lack of deep layer shear could/would be a limiting factor to storm development/sustainability. > 4th OF JULY WEEKEND: steamy for the 4th. Showers, storms likely Fri night and Sat. With the upper level ridge shifting from the northern plains to across the upper mississippi river valley Fri, a stronger southerly fetch sets up. Sfc dewpoints on the climb, likely reaching/pushing past 70 degrees. Increasing moisture transport with PWs upwards of 1 3/4". +1 to +2 in NAEFS and EC PW anomalies. Going to be humid for the 4th as a result, but with highs currently expected to top out around 90, heat indices will peak in the mid to upper 90s. Very uncomfortable, but not quite heat advisory. Still, with it being a holiday and lots of outdoor activities, a lot of care should be taken to protect yourself, family and friends from the heat. The heat/humidly portends to an increasingly unstable airmass - the grand ensemble lays out 2500-3000 J/kg of MUCAPE for Fri afternoon. However, not much wind shear to compliment the instability. There will be a low level cap to contend with too, which might not erode until late in the day. Whether general airmass storms could kick off is uncertain. GEFS and EPS still on track to lift a shortwave trough out of the southern rockies Friday, across the plains and then over parts of the upper mississippi river valley overnight Fri/Sat. GEFS is stronger overall with the feature. All have a related sfc cold front, but some small differences in timing/location. The upshot is a more expansive area of pcpn relating the shortwave and deeper forcing with the shortwave and north of it`s associated sfc low. Convection would still fire along the front, but coverage is more questionable. Current timing places the higher rain threat overnight Fri through Sat. That said, doesn`t look like a "washout" for Sat. For Sunday, most of the ensemble members layout a westward hanging sfc trough that could be the focus for continue rain generation. Where this would track is uncertain with not much agreement between the GEFS and EC. Could be mostly dry, could have persistent shower/storm chances. Overall, steamy start to the holiday weekend and a cooler end. Highest rain chances late Friday night into Sat. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 609 PM CDT Tue Jul 1 2025 Light winds overnight mostly remain out of the west potentially varying southwest. Scattered cumulus builds again Wednesday. VFR expected area wide through the 02.00Z TAF period. Potential for MVFR near 03.06Z primarily in central Wisconsin. Fog potential along the Wisconsin River Valley (KOVS) early Thursday morning. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Ferguson AVIATION...JAR