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
42
447 FXUS63 KARX 111149 AFDARX Area Forecast Discussion National Weather Service La Crosse WI 649 AM CDT Sat May 11 2024 .KEY MESSAGES... - Warm Sunday with afternoon-evening shower/storm chances (30-50%). Highs could push into the mid 80s for some river valley locations. - Cooler Monday with rain chances lingering (mostly south of I-90). - Periodic rain chances for the new work week with temps expected to hug close to the seasonable normals (around 70). && .DISCUSSION... Issued at 225 AM CDT Sat May 11 2024 * SUNDAY/MONDAY: Warm Sunday, afternoon-eve shower and storm chances (30-50%). Shower chances linger south Monday, cooler/seasonable. Upper level shortwave ridging set to drop southeast across the region Sunday. 850 mb temps progged to warm from around +4 C at 12z Sat to +13 C by 18z Sun. South, southwesterly fetch will help with the warming, all ahead of a cold front dropping southeast across the upper mississippi river valley for the afternoon/evening. Mixing is fairly deep for the afternoon, promoting drying and increasing wind gustiness, but will also help in the warming. 11.00z HREF paints a 40-70% chance for highs to push north of 80 degrees for all locations along/south of I-94. River valley locations (sandier soils) likely to have the largest bump in temps and could see some mid 80s. A taste of summer, minus the humidity. Back to the cold front...this sfc boundary is associated with an upper level shortwave trough which is set to slide across far northern parts of the region Sun/Sun night. Fgen along the front is meager, mostly low level, while the bulk of the low level thermodynamics is off to the east. There will be instability to play with as both the GFS and NAM paint 1000-1500 J/kg of SBCAPE by mid afternoon. Checking out the forecast soundings, deep mixing will promote some drying - so these CAPE values could be too high (dewpoints could be over forecast by the models). No shear to speak of. So a weakly convergent frontal boundary, not much for upper level support, but some instability to work with, suggests at least chance pops for showers/storms (30-50%). The front lays up west-east across northern IA/southern WI on Monday. A shortwave trough in the southern portion of the flow will meander across the southern plains and mid mississippi river valley, working on the boundary and helping to spark another round of showers/storms along it. Rain chances look more widespread with a more moist airmass to work on (pws climb to 1 1/4"). MUCAPES upwards of 500 J/kg with (again) not much for shear. Medium range guidance holds most of the rain chances south of I-90 with the pcpn threat shifting east by mid evening. * NEW WORK WEEK: progressive upper level flow, periodic rain chances, seasonable temps A variety of perturbations in the upper levels of the atmosphere are set to shift west-east across the CONUS for the new work week. GEFS and EPS showing some differences in placement/timing of the potential rain makers. Model blend thusly "smears" the pcpn chances due to the disagreements - spreading the threat out over several days while also holding lower end chances. Confidence also takes a hit in highlighting any period for having higher chances (or dry for that matter) - at least at this time. Will continue to ride the blend, but expect some refinement to the forecast as we move into the early part of next week. As for temps, after what looks to be a warm day Sunday temps are progged to settle back to more seasonable levels (or a few degrees above). That said, still a lot of spread in the ensemble members and certainly some adjustments for pcpn/no pcpn to be had - which isn`t clear. Again, will let the blend make the call for now. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 650 AM CDT Sat May 11 2024 VFR expected through the 11.12Z TAF period. Northwest winds slightly increase today primarily west of the Mississippi River. These winds wane tonight, eventually turning out of the south near 12.00Z or shortly thereafter. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ DISCUSSION...Rieck AVIATION...JAR