859
FXUS63 KARX 072352
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
652 PM CDT Sun Jul 7 2024

.KEY MESSAGES...

- Isolated to scattered showers/storms are possible over the
  next few days, with rain chances gradually lessening for
  mid/late week. Most hours will be dry, though, and the risk
  for organized heavy rain/severe weather is low.

- Near to below average temperatures early this week will trend upward
  by next weekend.

- Minor to moderate flooding continues along the Mississippi
  River, but river levels will be falling gradually over the
  coming week.

&&

.DISCUSSION...
Issued at 155 PM CDT Sun Jul 7 2024

This Evening - Wednesday:

GOES water vapor channel and RAP 500 mb heights show a broad trough
extending from the northern Rockies into the western Great Lakes
early this afternoon, with several embedded vorticity maxima
noted across the Dakotas into Minnesota. Surface analysis early
this afternoon showed a diffuse boundary across western IA/MN.
SPC mesoanalysis indicated pockets of 1000 J/kg MLCAPE along
with 20-25 kts of effective shear as of 2 pm. Within minimal
inhibition, isolated to scattered showers/storms are possible
this afternoon into tonight, although lift to help generate
organized storms this afternoon is nebulous. There is a
slightly stronger synoptic lift signal overnight from northeast
Iowa into central Wisconsin ahead of the trough axis. Any
storms should be subsevere, although gusty winds/small hail
cannot be ruled out. Although rain amounts overall will be light
spatially, localized amounts of 1 to 2" could occur with slow
moving storms. With light boundary layer flow, patchy fog could
develop early Monday, but confidence is low given uncertainty in
cloud/precip coverage.

Additional isolated to scattered storms are possible Monday
afternoon with diurnal destabilization beneath the mid-level cold
pool/trough. Low, mainly diurnal shower/storm chances continue
into mid-week within the broadly cyclonic flow. However, severe
storm potential should be low as both shear/instability are
fairly marginal. Will have to monitor the remnants of Beryl, as
guidance lifts this system northeastward by mid-week towards
the Great Lakes trough. Current multi-model global ensemble
forecasts suggest the bulk of the rainfall will skirt south
across the Mid-Mississippi Valley into the Great Lakes/Ohio
Valley with less than a 10% chance for at least 1/2 an inch of
rain across far southwest Wisconsin on Wednesday. Temps through
mid-week will generally be near to below average.


Thursday - Sunday:

Mid-level heights will begin to build late this week into the coming
weekend as the broad troughing across the Upper MS Valley loses its
influence. As this occurs, there is little signal for meaningful
rainfall late this coming work week. By next weekend, increasing
quasi-zonal to northwest mid-level flow may develop across the Upper
Midwest along the periphery of the strong ridge centered over the
Rockies. Any embedded shortwaves interacting with the moist,
unstable environment could result in showers/storms, but
predictability in these details is very low at this time. Otherwise,
the pattern favors rebounding temps back above average heading into
the weekend, although spread in the model suite also increases,
especially heading northward, likely due to uncertainty in the
amplitude/orientation of the flow and timing of shortwave
troughs/convection. However, some locations could be back up near 90
by later in the week or next weekend. NBM probabilities for 90F
temps increase to 20 to 60% across parts of northeast Iowa,
southwest into central Wisconsin and the immediate Mississippi River
Valley by next Sunday.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 643 PM CDT Sun Jul 7 2024

A line of storms extends from southwestern Houston County in far
southeast Minnesota to southwestern Chickasaw County in
northeast Iowa. Have been optimistic with VCTS at KLSE till
0200Z with more northeastern storm, may need to be quickened
however. Atmosphere is conducive for storm continuing.
Difficulty will be strength, i.e., thunder vs. shower.
Broad shield of showers extends to the northwest of this main
line, soon affecting other TAF site of KRST.

Otherwise, question becomes lowering visibilities with fog
overnight into the early morning hours. Have lowered
visibilities to MVFR with limited window of saturation and light
winds expected but will be subsequent detail to monitor in
coming TAF (08.06Z). May need to lower flight rules further for
fog depending on storm exit.

&&

.HYDROLOGY...
Issued at 347 AM CDT Sun Jul 7 2024

The Mississippi River is noting falling river levels from north
of Brownsville, MN with Lake City, MN falling below flood stage.
Locations near crest from Brownsville, MN on south to
Guttenberg, IA. River stages are expected to fall into this
week from northeast Iowa and southwestern Wisconsin on northward
along the Mississippi River. Generally lighter rainfall amounts
of up to around 0.5" from now through Tuesday are expected,
with locally higher amounts possible with any storms that pass
over. May have to watch the remnants of Tropical Storm Beryl for
more substantial rainfall across southwestern WI/northeast IA
for Tuesday night and Wednesday. However, the probabilities for
heavier rainfall with this system remain low as guidance keeps
much of the heavier rainfall farther south and east of the local
area.

&&

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

&&

$$

DISCUSSION...JM
AVIATION...JAR
HYDROLOGY...Naylor