209
FXUS63 KARX 162342
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
642 PM CDT Mon Sep 16 2024

.KEY MESSAGES...

- Summery warmth with above normal temps through the work week,
could continue over the weekend and into next week (only tempered by
rain chances). Not as humid.

- Dry conditions through Wed with next shower/storm chances Thu
night, more favored west of the Mississippi River. More rain chances
for the weekend into the early part of next week - how widespread is
uncertain.

&&

.DISCUSSION...
Issued at 130 PM CDT Mon Sep 16 2024

OVERVIEW: stout upper level ridge will be the main weather influence
through the middle part of the week, keeping it dry with ample
summer warmth. Medium and long range guidance then suggest that a
shortwave will lift northeast out of the long wave trough over the
west coast, gradually getting caught up in the northern stream and
pushing east/northeast across southern Canada. Southward extension
of the shortwave could slide eastward across the region, through the
ridge, with resulting rain chances. Decent agreement in the GEFS and
EPS with bringing another shortwave trough out of the desert
southwest and across the upper mississippi river valley for Sun/Mon
with more zonal flow after that.


PCPN: med and long range guidance keying in on a shortwave trough
they want to bring from the west coast, across the northern plains
and then over southern Canada Thu night. WHile the bulk of the upper
level forcing would stay north of the local area in this scenario,
an associated southward running sfc boundary could/would interact
with a feed of southerly moisture (aka, low level moisture
transport) and ribbon of instability to spark showers and a few
storms. The deterministic and bulk of the EPS and GEFS ensemble
members all layout some QPF for the local area, although how much of
a deterrent the ridge/dry air will play is uncertain. The setup does
favor higher chances west for Thu night while also keeping most of
any strong/severe storm risk even farther west. While rain would be
welcomed by most, this doesn`t look like a soaker. The grand
ensemble paints only a 10 to 30% for more than 1/10"...although
convective nature of the pcpn could produced localized higher
amounts.

Moving into the weekend, more mixed messages in the long term
guidance for how quick/where they want to spin their next series of
shortwaves from the southwest. Deterministic runs of the GFS and EC
propose holding the bulk of the rain chances off until the start of
the new work week, keeping much of the weekend "dry". Not a lot of
confidence here, but with support from over half of both suites of
ensemble members for at least some rain threat this weekend, will
hold with the NBM for rain chances.


TEMPS: the taste of summer will continue for much of the week as the
long range ensembles continue to paint 70-100% for highs warming to
80+ degrees into Friday. Potential cooling for the weekend, but
mostly based on increased rain chances/clouds - and that is not a
certainty. Humidity will be lower compared to the weekend as sfc
dewpoints drop as the ridge of high pressure moves overhead. So
unseasonably warm, but not oppressively so. The 8-14 day outlook
from CPC suggest the warmth with continue with a 50-70% for above
normal temps persisting through the last week of September.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 642 PM CDT Mon Sep 16 2024

VFR conditions are forecast through the TAF period with some
high clouds moving across the region. South/southeast winds
increase into the day Tuesday and a few increased wind gusts to
around 20 kts may be possible at KRST.

&&

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

&&

$$

DISCUSSION...Rieck
AVIATION...EMS