640
FXUS63 KARX 102347
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
647 PM CDT Fri May 10 2024

.KEY MESSAGES...

- There will be showers and scattered storms this afternoon and
  evening. These will produce gusty winds. The strongest storms
  might produce isolated damaging winds.

- Good viewing conditions are expected for the auroras tonight.

- Additional showers and storms expected from Mothers Day into
  Monday evening. Severe weather is not anticipated at this
  time.

&&

.DISCUSSION...
Issued at 231 PM CDT Fri May 10 2024

This Afternoon and Evening - Showers and Scattered Storms

A 500 mb shortwave will move southeast through the Upper Mississippi
River Valley. 10.12z HREF probabilities of greater 40 dBZ and
greater than 50 J/kg MUCAPE ranged from to 30 to 50% west of the
Mississippi River and 50 to 90% across central and western
Wisconsin. The highest probabilities are between 5 PM and 10 PM.
Soundings continue to show an inverted V sounding in the sub-
cloud layer. In addition, there will be rather steep 650-900 mb
lapse rates (8-10 C/km), so we are looking at gusty winds from
these storms. The HREF 4-hour maximum 10 meter AGL winds were
mainly below 40 knots. The latest SPC Day 1 Outlook keeps
central and western Wisconsin, and southeast Minnesota in a
Marginal Risk (risk 1 out of 5) of severe weather. This makes
sense since a few of the stronger low-top storms might produce
isolated wind damage.

Overnight - Good viewing conditions expected for the auroras
tonight

The first of 7 Earth-directed coronal mass ejections arrived shortly
before noon. The solar wind has climbed to nearly 700 km/sec and the
density is over 27 protons/cm3. The interplanetary magnetic field is
currently south. The planetary K-index (Kp) has already
increased to 7. The Space Weather Prediction Center (SWPC)
continues to forecast that the Kp is expected to climb over 8
overnight. These values are favorable for our area to see
auroras.

10.12z models are in fairly good agreement that skies will be mainly
clear overnight. Temperatures would range from the upper 30s to mid-
40s. Northwest winds will be generally less than 10 knots. This will
slightly lower the wind chills. They are expected to range from the
mid-30s to lower 40s.

Saturday - Mostly sunny and dry

Saturday continues to show that high pressure will build across the
region. 850 mb temperatures will be 1 to 3C cooler, so high
temperatures are expected to range from the mid-60s to around 70.
Soundings continue to support slightly lower surface dew points, so
used the NBM 10th percentile to lower them some. This would lower
afternoon relative humidities into the 20s and 30s. The northwest
winds will be in the 10 to 20 mph range with wind gusts of 20 to 30
mph.

Mothers Day through Monday Evening - Additional showers and
storms expected

A Canadian cold front will move into the area during the afternoon
and evening of Mothers Day and linger over the area into Monday
evening. This front will be the focus for some showers and storms.
Like the past couple of days, the 0-6 km shear remains 25 knots or
less, so severe chances look rather low. High temperatures will
range from the mid-70s to lower 80s on Mothers Day and range from
the mid-60s to lower 70s on Monday.

Tuesday Night through Thursday - Much uncertainty

The 500 mb pattern becomes much more uncertain. Some models are
showing phasing between the northern and southern streams.
Others are showing little phasing between these two streams.
There is even some which have shortwave ridging over the area.
As a result, just stayed with the NBM for both temperatures and
precipitation.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 648 PM CDT Fri May 10 2024

A cold front continues to move through along with a band of
showers and thunderstorms. This precipitation band is mostly in
central and western portions of Wisconsin. Gusty winds are the
primary threat with these storms. Southwest winds will shift to
northwest winds after the front pushes through. These northwest
winds will continue through the TAF period. Some mid-level
clouds will be in the area for the next couple of hours before
clearing out for the overnight period.

&&

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

&&

$$

DISCUSSION...Boyne
AVIATION...Cecava