Sunrise 5:45 AM   Sunset 8:06 PM Moonrise 2:18 AM   Moonset 12:27 PM

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FXUS63 KARX 021737 AFDARX

Area Forecast Discussion National Weather Service La Crosse WI 1237 PM CDT Thu May 2 2024

KEY MESSAGES

- There will be a couple rounds of showers and scattered storms through this evening and then it dries out for late tonight and Friday. Like the past couple of days, severe weather chances for this afternoon and evening continue to look very low.

- Another round of showers is expected from Friday night into Saturday night. Rainfall amounts continue to look light with amounts less than a tenth of an inch.

DISCUSSION
Issued at 257 AM CDT Thu May 2 2024

This Morning - Showers and scattered storms

A 500 mb shortwave will move northeast through the area this morning. As this occurs, a 50 knot 850 mb jet will help increase the moisture across the region. There is strong consensus among the 02.00z HRRR members that precipitable water values will increase to around 1.2 inches this morning. The 6-hour 02.00z HRRR ensemble mean shows that there is a 50-80% chance of at least a half inch of rain along and south of Interstate 94 and 25 to 50% elsewhere. The greatest probabilities (20-40%) for 1 inch or greater is across southeast Minnesota and southwest.

While the 0-6 km shear is increasing to 50 to 60 knots of shear this morning, much of that shear is located below the inversion, so it will not be actually ingested into the storm updraft. In addition, most unstable CAPES will be generally less than 250 J/kg. As a result, severe chances look unlikely this morning.

This Afternoon into Tonight - Another round of showers and scattered storms

There will be northern stream 500 mb shortwave trough moving across western and northern Minnesota and southern stream 500 mb shortwave trough moving from the Mid Mississippi River Valley into the southern Great Lakes. The best 850 mb moisture transport will be found in southwest and central Wisconsin and northeast Iowa this afternoon and then shifts east of the area during the evening. As a result, the better probabilities (up to 30%) for an additional half or greater of rain will be in the aforementioned areas. The chances of an additional inch of rain will be less than 10% in these same areas.

With limited surface heating this afternoon, the 0-1 km mixed layer CAPES will likely remain below 500 J/kg. In addition, with the stronger winds aloft remaining north of the warm front, the 0-6 km shear will likely remain below 30 knots in the warm sector. Due to this, the threat for any damaging winds and/or large hail should remain largely isolated this afternoon and early evening.

High temperatures today will be mainly in the 50s north of Interstate 90 and in the 60s and lower 70s elsewhere.

Late Tonight and Friday - Still Looking Dry

Subsidence quickly builds across the area in the wake of the front tonight and this continues into Friday. As a result, the CAMs and ensembles are quickly drying out the area. This occurs west of the Mississippi River late this evening and across the remainder of the area overnight tonight. With mostly sunny skies expected for much of Friday, high temperatures will be in the mid- and upper 60s north of Interstate 94 and around 70 elsewhere.

Friday Night through Saturday Evening - Scattered showers. Rain amounts continue to look light

The 02.00z models continue to show that a broad longwave trough will move east through the area. With our area being on the southern extent of this trough, both forcing and 850 mb moisture transport remain rather weak in our area. The ensembles remain in good agreement that the area will likely see less than a tenth of an inch of rain.

For Early Next Week - Maybe severe weather

The models are in general agreement that a closed 500 mb low will eject out of the southwest US and move into the Northern Plains.
Ahead of this low, there appears to be a shortwave trough will move northeast through the Upper Mississippi River Valley and Great Lakes from Monday night into Tuesday. While the timing is not overly favorable to building instability ahead of this system, there should be ample shear and forcing for the possibility of severe weather. The Day 7 CSU probability of severe weather does climb into the 15 to 30 percent range for this time period, so this will be something to watch over the weekend.

AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
Issued at 1227 PM CDT Thu May 2 2024

Southeasterly winds will switch to northwesterly winds during the afternoon. These winds will stay out of the northwest until the overnight period, when southwesterly winds will take over and last through Friday morning. A band of rain will continue to move into central Wisconsin this afternoon. Scattered showers and thunderstorms will continue to be possible through the afternoon, however the favored areas for these to develop are in eastern Iowa and southern Wisconsin. CIGS are expected to stay MVFR to IFR for most locations through the day today. Skies will gradually clear up after midnight and by Friday mid- morning, skies will be clear across the area.

ARX WATCHES/WARNINGS/ADVISORIES
WI...None.
MN...None.
IA...None.

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