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000
FXUS63 KARX 180658
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
200 AM CDT Thu Apr 18 2024

.KEY MESSAGES...

- Another rainy day for most, especially along/south of I-90 with
80 to 100% chances and likely accumulations of around 1/4" or more.

- Blustery end to the work week with westerlies gusting to 35 mph
Friday.

- Colder weekend with highs only in the 40s Sat and freezing lows
for most Sat/Sun.

&&

.DISCUSSION...
Issued at 200 AM CDT Thu Apr 18 2024

* RAIN TODAY - highest chances, amounts south of I-90

Latest watervapor satellite imagery depicts elongated shortwave
energy stretching across the northern and central plains, helping to
power areas of showers (perhaps some thunder) over southwest
MN/western IA early this morning. A cold front is situated ahead of
the upper level forcing, running from northwest WI into central IA.
While the short/medium range guidance never really coalesce these
features together, the mix of lift with both helps drive pcpn in the
deformation region north of a sfc low (tracking east across the mid
mississippi river valley). Broad Fgen along the leading edge of the
shortwave and sfc front, but stronger/deeper in the south. Beefer
low level thermodynamics also lies along the front with the 850 mb
transport just ahead of it. CAMS and other short term models paint
their QPF where the greater forcing/saturation is expected - which
locally is mostly along/south of I-90 (80-100%). Amounts have
increased a bit and shifted east compared to previous days, but
looks reasonable given latest trend in the CAMS. 60 to 80% chances
for more than 1/4" south of I-90, with low end (10%) potential to
reach 1/2" over northeast IA.


* COLDER, DRIER WEEKEND - freeze temps likely for most Sat/Sun,
  blustery Friday (gusting 35 mph)

The region will be under the influence of an upper level trough for
the weekend...a very persistent, and consistent, signal in the long
range guidance. 850 mb temps tumble sub zero tonight, likely not
moving into the positive digits until later Sunday night. GEFS and
EPS members have over 90% of their members holding highs under 50
degrees Sat with a slight bump into the 50s for Sun. Morning lows
Sat/Sun show a 60 to 100% chance for freezing temps. Depending on
cloud cover and winds, Frost and/or Freeze headlines may be needed.
If you are an early season planter, measures should be taken to
protect tender vegetation.

Another upper level shortwave trough is set to drop in from southern
Canada Fri night. Saturation will be a challenge with guidance
holding the deeper moisture to the north. Lapse rates are on the
increase and will result in some instability, but questions on
whether enough moisture will be available this far south to produce
more than some clouds is uncertain. The EPS is dry, with essentially
all of its members keeping any QPF north (and what there is is
meager). GEFS is a bit more optimistic on chances with some of the
members dropping pcpn and probabilities for measurable QPF from 10
to 40% north of I-94 Fri afternoon/evening. NBM (model blend)
continues to trend dry locally, but this seems like a system that
might be punchy enough to overcome the perceived lack of saturation.
Will stick with the blend for pcpn chances for now, but wouldn`t be
surprised if at least some low end chances start to creep farther
south over the next 24 to 36 hours. All in all though, amounts would
be minor.

While the local area could avoid any rain chances Friday, the
tightening sfc pressure gradient ahead of the shortwave will make
for a blustery day. Gusts from daytime mixing in both the GFS and
NAM blow into the 30s mph. The EPS is more bullish on the gust
potential, suggesting they could top around around 40 mph. Doesn`t
look like wind advisory at this time - but certainly a "blowy" end
to the work week.


* WARMING NEXT WEEK: pcpn chances return Mon-Tue

Shortwave ridging presses in Monday, and should see another small
bump in temps (more seasonable). Long range guidance then favors a
quick moving upper level trough Monday afternoon, lingering into
Tue. Good shot for showers in this scenario. Not a lot of instability
indicated, so lower end thunder chances at this time. Post the
trough the EPS and GEFS develop a stronger upper level ridge for the
middle/latter part of next week. Temps trending up as a result with
the upper 25% of the GEFS and EPS members warming into the 60s and
70s. CPC 6-10 and 8 to 14 day temp outlooks also trending toward
warmer, above normal temps for the 2nd half of April.


&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1035 PM CDT Wed Apr 17 2024

Ceilings will become MVFR overnight. These lower ceilings will
likely persist through much of Thursday before becoming mainly VFR
in the late afternoon and early evening.

Showers will move into the area after 18.07z and then linger through
mid-afternoon Thursday. Rainfall amounts will be less than a quarter
inch.

Northwest and west winds will be mainly in the 10 to 20 knot range
through the TAF period.

&&

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

&&

$$

DISCUSSION...Rieck
AVIATION...Boyne