725
FXUS63 KARX 131120
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
620 AM CDT Sat Jul 13 2024

.KEY MESSAGES...

- Multiple rounds of storms possible through Monday. The
  environment will be favorable for strong to severe storms,
  but confidence in timing/location of storms remains low.

- A hot, humid airmass will be in place through Monday with peak heat
  indices in the 90s to near 100.

- A much cooler, drier period is likely for mid to late next
  week.

&&

.DISCUSSION...
Issued at 333 AM CDT Sat Jul 13 2024

Thunderstorm Potential Through Monday Night:

A complex, lower confidence forecast exists over the next few days
with respect to storms. The region lies on the edge of strongly
unstable airmass within an energetic west to northwest flow along
the periphery of the western US ridge. As of early this morning,
areas of convection were ongoing across the Dakotas into western
Minnesota in a region of modest moisture transport/warm
advection associated with a few subtle waves. There is
considerable uncertainty how these storms will evolve heading
into the daytime hours with some model solutions suggesting
rejuvenation of storms as they progress along the edge of the
stronger capping/instability axis. However, CAMs show
significant differences in the strength/timing and location of
storms by afternoon. Additional storms could form overnight
within broad warm advection, perhaps focused closer to the
surface low farther north across Minnesota, and again
progressing along the instability axis, but confidence is low
given the lack of strong low-level jet/forcing and possible
impacts from prior convection. Convective trends will need to be
evaluated through the day. Damaging winds would be the primary
threat with organized convective systems that have well
developed cold pools, with some hail potential with any more
discrete storms, especially with steep lapse rates. The
environment would support high rain rates, and locally heavy
rainfall (2-3") could occur in spots, especially where
repetitive rounds of storms occur.

There is less of a signal currently for storms on Sunday with a lack
of a stronger shortwave to help ignite storms and some capping
present. However, will maintain some low chances for storms given
the degree of instability present and uncertainty in storm
evolution through tonight which could impact downstream
initiation Sunday, such as outflow boundary location. SPC has
maintained a broad level 1 of 5 severe risk, which seems
reasonable right now given the lack of focus.

There`s a greater signal for additional storms Monday/Monday
night as a more pronounced shortwave trough drops southeast,
dragging a cold front across the area. Again, capping will
increase with southwestward extent (and higher storm chances
northward), but the shear/instability parameter space would
support severe storms and possible MCS development.


Hot, Humid Through Monday:

A sticky, hot period is likely through the weekend into Monday as
the region lies on the periphery of a strong ridge centered over the
Four Corners region. Spread in model guidance is fairly small with
mid 80s to low 90s temps expected and peak heat indices in the
90s to locally near 100 in spot. However, being situated on the
periphery of the ridge, any storms or debris clouds impacting
the area during the daytime hours could influence on temps.


Cooler, Drier Tuesday

Northwest flow will amplify for mid to late next week with a much
cooler, drier working south as Canadian high pressure builds south.
Seasonably cool highs in the 70s and low 80s are expected with lows
falling back into 50s.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 620 AM CDT Sat Jul 13 2024

Main taf concerns is the potential for thunderstorms at both RST/LSE
taf sites this afternoon and tonight. Latest mosaic radar shows
complex of showers/storms over central Minnesota tracking southeast.
Hi-resolution models suggest a weakening trend with this complex of
showers/storms. However...there is weak moisture convergence/lift
over the area this morning/early afternoon. Depending on track of
complex...there could be a low chance a few showers/isolated storm
to impact the RST/LSE taf sites. For now will mention vicinity of
showers at RST taf site late this morning/early afternoon. Next
concern is redevelopment of showers/storms tonight...though focus
appears to be over western/central Wisconsin which would track north
of taf sites. However there is uncertainty on where
development of convection occurs. At this time...confidence is
low if this convection impacts the RST/LSE taf sites and left
mention out of tafs. VFR conditions are expected at both taf
sites through the taf period. However...if any convection occurs
at taf sites...brief periods of MVFR/IFR conditions could
occur.

&&

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

&&

$$

DISCUSSION...JM
AVIATION...DTJ