240
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 HREF members that precipitable water values will
increase to around 1.2 inches this morning. The 6-hour 02.00z
HREF 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.

&&

$$

DISCUSSION...Boyne
AVIATION...Cecava