290
FXUS63 KARX 132326
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
628 PM CDT Mon May 13 2024

.KEY MESSAGES...

- Smoke from Canadian wildfires continue to impact the local
  area with hazy conditions/milky skies tonight.

- Rain chances linger far south tonight and Tuesday, much drier
  air to move in from the north.

- Rain chances favorable, but still light (50-70% chance of
  0.10+) Wednesday night into Thursday with the weekend still
  unsettled for now.

&&

.DISCUSSION...
Issued at 224 PM CDT Mon May 13 2024

Overview:

Water vapor satellite imagery, 500mb heights, and lightning
showed a closed low over the Mid-Missouri River Valley with
another area of closed low pressure over Hudson Bay. Lightning
was noted over parts of IA/MO into IL, with clusters of storms
farther south across TX/LA/MS/AL. The first surface front was
over parts of northern IL with a reinforcing push/wind shift
moving through as the wave to the northeast pushes through with
dewpoints in the 30s pushing south and dewpoints in the 50s to
around 60 lingering across parts of eastern Iowa and southern
Wisconsin.

Smoke Tonight - Rain chances tonight/Tuesday:

Visible satellite imagery from 13Z this morning showed an expanse of
smoke across the local area, however by 15Z, local visibilities had
improved some.  Hazy conditions with some visibility reductions will
be possible into the overnight hours. The latest RAP Near-
Surface Smoke forecast shows a north to south push of improving
conditions. By 06Z, parts of northeast Iowa and the PDC area
could see some reduced visibilities. Some low values of
particulates will linger area-wide 14.09-16.00Z Tuesday. Air
quality alert for parts of MN/WI/IA remain in effect this
evening.

The trough over the Upper Mississippi Valley phases with the mid-
tropospheric low over the Mid-Missouri River Valley, but then closes
off again off over IL shifting east through the day Tuesday.
Showers and a few storms will continue to graze parts of the
southern forecast area today, then a few showers will persist
until the storm system shifts east into Tuesday. The general
consensus with the hi-res models is for the bulk of the activity
to remain southeast of the forecast area Tuesday. The 13.12Z
HREF was a bit farther south with the precipitation compared to
the 13.00Z run. The RAP is a little more aggressive farther
north. For now will hold on to some pops in the south and
monitor push of drier air and northward extent in the short
term.

Temperatures Tuesday and Wednesday should be seasonable in the 60s
to lower 70s.

Rain chances mid to late week:

The trough over the Pacific Northwest is forecast through the Plains
Tuesday night toward the Upper Mississippi Valley Wednesday night.
The low level jet increases and 850mb moisture pools ahead of the
cold front from MN/wrn IA/ern KS Wed.  Moisture transport increases
locally Wednesday night into Thursday.  Deepest moisture and
stronger moisture transport vectors remain to the south across parts
of MO/IL. There appears to be enough vorticity/warm air advection
and limited instability (500J/kg) with the front for scattered
showers and a few storms. 0-6km is generally limited...20-30kts,
however there is a period of time Wednesday night with higher shear
values north of I94, however instability is quite low then.  Will
maintain likely shower/storm chances Wednesday night into Thursday.
Forecast soundings hint that a few showers could re-develop
Friday/Friday night in the northwest flow aloft.

For the weekend, we are still unsure of if the pattern will be more
zonal locally or have a trough coming through. Due to this
uncertainty of dry vs. a trough and timing differences, we do
have rain chances in for the weekend, but this will be refined
as we hone in on the synoptic patern. The NAEFS/EFI remain on
the lackluster side. Weekend temperatures appear to be
seasonably warm in the 70s.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 628 PM CDT Mon May 13 2024

Main impact to aviation initially remains wildfire smoke that has
dropped visibilities into the MVFR range at times. Near-surface
smoke guidance suggests this area should continue to improve with a
cleaner air source from the northeast as area falls under influence
of upper low circling to the south. Will continue trend based on
this with improvement this evening.

Otherwise just high clouds streaming off of larger convection region
to the south. Airmass locally remains on drier side so post-smoke
VFR pattern looks reasonable into Tuesday.

&&

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

&&

$$

DISCUSSION...Zapotocny
AVIATION...Shea