Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 250837
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
337 AM CDT Wed May 25 2022

.DISCUSSION...(Today through Tuesday)
Issued at 337 AM CDT Wed May 25 2022

Key Messages:

 - Widespread rainfall exits area Thursday

 - Warmer conditions expected this weekend

Rain showers continue into Thursday...

Surface observation analysis shows the low pressure system over
eastern Kansas and associated warm front stretching into north
central Illinois. The low is anticipated to lift to the northeast
throughout the day today. The upper-level system moves eastward
through the southern Great Plains becoming closed off. Meso models
suggest that the showers become more scattered by mid-afternoon.
Although, the persistent cloud cover would limit surface heating
leading to fairly stable conditions. The question is how far north
does the warm front progress. Much of the region is expected to
remain in the cooler and more stable airmass within the northwestern
quadrant of the surface system. However, portions of far
southwestern Wisconsin and northeast Iowa may get some instability
to graze by with MUCAPE values near 500 J/kg. This could result in
some rumbles of thunder, but severe weather is not expected.

On Thursday, precipitation chances could linger with support of a
deformation zone as hinted at in most of the meso models. Heading
into the evening, precipitation chances will be on a diminishing
trend and move off to the east as the upper-level system moves into
the Ohio River Valley region with ridging building in from the west.
Then quiet conditions are expected to end the work week with
temperatures on the rise heading into the weekend.

Warming up through the weekend...

Blended model guidance has afternoon high temperatures topping out
in the 70s and 80s. While precipitation and cloud cover will impact
the surface heating, the main source of uncertainty comes from the
upper-level flow and associated surface fronts. How amplified and
progressive the pattern becomes will have great implications on the
temperature as well as the precipitation forecast. But the general
idea is that the previously mentioned mid-level ridge will move over
the region this weekend then slide off to the east for the new work
week.

Precipitation chances are introduced mainly north of I-90 on
Saturday as an embedded short wave trough slides over the ridge
while flattening the upper-level flow as a result. With varying
model solutions on the timing and strength of this next weak wave,
precipitation chances are on the low side (20-45%). From Sunday into
mid-week, chances for showers/storms look to remain mainly across
the northwest portion of the forecast area with higher chances even
further off to the northwest. Under a southwesterly flow, the
precipitation chances will depend on the position of the surface
front. This looks to be fairly persistent holding off to the
northwest with a near steady, unprogressive flow aloft.

Heading into the new week, confidence has increased that warm
conditions will persist into midweek, just not certain on how long.
WPC`s cluster analysis for Tuesday shows a trough off to the west
and predominant ridge over the eastern CONUS with 500 mb height
anomalies nearing 200 m. The cluster means for maximum temperatures
have near 10 degrees of difference between different solutions for
Tuesday. Looking at Wednesday, there is even more uncertainty.
Specifically for at the EPS guidance, the 25th to 75th percentile
range is about 15 degrees for much of the region for maximum
temperatures.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1032 PM CDT Tue May 24 2022

VFR conditions erode to MVFR near 25.12Z due to lower cigs.
Precipitation expected to remain for much, if not all, of the
forecast period (25.06Z-26.06Z). High resolution models disagree
on exit of precipitation, with more scattered precipitation on
backside of surface low into Thursday. Intensity will be heavier
at RST at times, especially in the next few hours. Winds increase
at both TAF sites as surface low approaches Wednesday morning,
weakening as surface pressure gradient weakens late Wednesday
afternoon. Flight restrictions expected to deteriorate to IFR and
possibly LIFR Wednesday afternoon with lower cigs. Have not
included LIFR restrictions for current TAF issuance due to
decreased confidence and increased forecast hour. However, with
future forecasts LIFR conditions may affect RST initially
Wednesday afternoon and LSE Wednesday evening. Lowest vsbys of 3SM
expected Wednesday afternoon, coinciding with IFR cigs.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

DISCUSSION...Peters
AVIATION...JAR


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