171
FXUS63 KARX 150015
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
715 PM CDT Sat Sep 14 2024

.KEY MESSAGES...

- Summer warmth through much of the new week with highs in the low
to mid 80s.

- Most locations will stay dry into Wed with increasing chances from
west to east moving into next weekend.

&&

.DISCUSSION...
Issued at 140 PM CDT Sat Sep 14 2024

OVERVIEW: models remain in lockstep with reestablishing the upper level
ridge across the upper mississippi river valley as we move into the
new work week. This holds through the better part of the work week
despite a west coast longwave trough periodically tossing shortwaves
at the ridge`s western flank. The GFS and EC suggest another trough,
this one dropping out of western Canada, will finally kick the ridge
axis east moving through next weekend.

Upshot to this pattern is persistent summery warmth with mostly nil
to low end rain chances until next weekend.


PCPN: north-south running piece of upper level energy will continue
to fire scattered/areas of showers into the evening, mostly north of
I-94 and diminishing into the overnight. RAP/HRRR soundings continue
to suggest weak instability will build for the afternoon/early
evening hours - so a thunderstorm or two remains a possibility.

Some of the short/medium range guidance continues to suggest that a
very weak ripple or two could still rotate north/northwest of what
is left of Francine for Sun/Mon - producing a smattering of light
qpf here and there. Not as much saturation to play with though, per
bufkit soundings and time/height x-sections. NBM keeps pops around
10% with a smattering of 20% here and there. For now, will lean into
a "dry" forecast. Even if a few sprinkles are realized Sunday, most
locations will be missed.

Moving into the new work week, the ridge should provide at least a
few dry days for the region. Recent deterministic runs of the EC and
GFS then suggest mostly western parts of the forecast area could
start seeing low end rain chances by Wed - as both models spin bits
of shortwave energy out of a west coast trough. However, the bulk of
both models` ensemble members suggest they area will stay dry. In
addition, the grand ensemble model blend holds measurable rain
chances from 10 to 30% mostly along/west of the Mississippi river
starting late Wed night. Only by the weekend do these chances start
to increase as a trough from western Canada pushes the ridge axis
east. The NBM still looks a bit aggressive with how far east and how
soon its spreads rain chances over the forecast area...and think
there is likely a better shot for most locations to stay dry until
the weekend. For now will continue to side with the NBM for chances.


TEMPS: the models` enthusiasm for the continued warmth has grown over
the past few days. Probabilities for 80+ degree days in the grand
ensemble of models have moved to 70-100% into next Friday. Looking
at the EPS and GEFS ensembles, they also show increasing consensus
for the warmth with little variation between individual members - as
little as 10 degrees between 10 and 90% outcomes. Low to mid 80s
looks like a safe bet given the trends with some of the area`s
warmer locations likely topping out in the upper 80s to near 90 on a
few days.

After a relatively humid weekend, drier air will return with the
ridge dropping sfc tds from the mid to upper 60s to the upper 50s to
around 60 for the work week. So while the heat cranks up a few
notches, the humidity will be lower.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 715 PM CDT Sat Sep 14 2024

Some mid/high level clouds will persist into tonight, but
ceilings are expected to remain VFR. Generally dry conditions
are likely through the TAF period, but isolated showers will
linger into this evening, and there is a very low chance
(10-15%) for an afternoon shower or storm on Sunday. Patchy fog
(20-40% chance) could result in MVFR visibilities in spots
early Sunday, but confidence is too low to include at this time.
Winds will generally remain southeasterly.

&&

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

&&

$$

DISCUSSION...Rieck
AVIATION...JM