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000
FXUS63 KARX 260810
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
310 AM CDT Fri Apr 26 2024

.KEY MESSAGES...

- An active weekend of weather expected with multiple periods of
  showers/storms, favoring today/tonight and again later
  Saturday into Sunday. Localized heavy rain (2" or more) with a
  few strong/severe storms possible.

- Windy at times today through the weekend. Gusts to around
  40-45 mph possible across southeast Minnesota and northeast
  Iowa today.

- Occasional shower/storm chances continue into next week with
  above average temps.

&&

.DISCUSSION...
Issued at 310 AM CDT Fri Apr 26 2024

Today and Tonight:

An area of low pressure continues to move into the Central Plains.
This system will move into the Great Lakes region during the day
today and into Saturday. Accompanying this low will be strong
winds just above the surface, 40 to 50kts between 3000 and
5000ft. This will result in surface wind gusts ranging from 30
to 40mph with potential to go higher if deeper mixing occurs.
PWAT values will increase during the day today and range from 1
to 1.3", with the highest values occurring tonight into
Saturday morning. The first wave of precipitation is expected to
begin to move into the area during the mid morning to afternoon
timeframe. There continues to be some delay in the onset of the
rain as dry air remains in place in the lower levels. As
previously mentioned, the strong winds just above the surface
could be realized due to rain falling through this dry layer and
bringing those winds down to the surface. If deeper mixing is
realized, a short term wind advisory may be needed for portions
of southeast Minnesota and northeast Iowa. During the afternoon
and evening, another round of rain moves through. The last wave
moves through this evening through the early morning hours on
Saturday. For this last wave, the low will be just west of the
area. Storms would have started in western Iowa and followed
the trajectory of the low into the Upper Mississippi River
Valley. For our area, this will be when the greatest surge of
PWATs and dewpoints will be. Current forecasted dewpoints
during this timeframe are between 55 and 60F for areas south of
I-90. At this same time, instability will increase as a warm
front lifts north. Given these parameters, this particular wave
would be the best chance at seeing some form of severe weather.
At the moment, SPC has the areas south of I-90 in a marginal
(level 1 out of 5) risk for severe weather with winds and hail
being the primary potential threats.

Saturday-Monday:

The first shortwave will lift off to the northeast by Saturday
morning with weak shortwave ridging in its wake. This should lead to
overall drying conditions with gusty southwest winds and warming
temps through the 60s and 70s, potentially near 80 across
southwest/central Wisconsin. Winds could gust near or above 40
mph in spots as mixing deepens.

The stronger lift likely won`t arrive until Saturday night as
stronger forcing/moisture transport with the upstream wave arrive.
At least moderate instability should build along/south of the
boundary. Uncertainty exists with the extent of diurnal convection
with nebulous forcing until the evening or overnight hours. RAP
soundings in the warm sector show relatively straight
hodographs by late afternoon before trending messier in the
evening. A conditional risk for severe storms exists near the
boundary if sustained storms can initiate during the
afternoon/evening. Otherwise, elevated storms north of the
boundary later overnight could pose a hail threat. With NAEFS
precipitable water values in the 97- 99% range relative to climo
and moisture intersecting the boundary, localized rain amounts
could exceed 2", especially across northeast Iowa into southwest
Wisconsin in proximity to the boundary.

Widespread showers/storms will impact the area into Sunday as the
surface low/shortwave lift north. At least a modest potential
for strong to severe storms exists as the warm sector tries to
spread north. However, considerable uncertainty exists with the
extent of destabilization, so confidence is low. Scattered
showers/storms could persist into Monday before the cold front
clears to the east.

Tuesday-Friday:

An active quasi-zonal flow is forecast through the rest of the work
week with model guidance generally indicating a few embedded
shortwave troughs within the stronger mid-level westerlies impacting
the northern tier of states. Predictability of the individual
troughs is relatively low at this range, but trends favor above
average temps and periodic shower/storm potential.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1040 PM CDT Thu Apr 25 2024

Initial quiet conditions with mostly clear skies will make way
to an impending cloud deck seen over western Iowa at TAF
issuance. Associated flight restrictions march northeast
overnight, reaching local counties in northeast Iowa near
26.12Z. A quick drop to IFR is expected after MVFR becomes
realized. The southwest to northeasterly trajectory brings MVFR
ceilings along the Mississippi River Valley by the early
afternoon.

Thunder potential remains in flux. While confidence within the
local area is moderate-high, nailing down the exact location
remains a challenge. Therefore, given the 18 hour forecast
window, have omitted any mention for thunder at 26.06Z TAF.

Ongoing Low Level Wind Shear expected to continue into the early
morning hours at KLSE. Models would suggest another bout
returning tonight, as surface winds calm and the low level jet
persists. Timing of frontal features and associated jet will
aide coming forecasts in subsequent LLWS potential.

&&

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

&&

$$

DISCUSSION...Cecava/JM
AVIATION...JAR