NWS-La Crosse Forecast Discussion


						FXUS63 KARX 262337

Area Forecast Discussion
National Weather Service La Crosse WI
637 PM CDT Tue Sep 26 2023

.DISCUSSION...(This evening through Tuesday)
Issued at 257 PM CDT Tue Sep 26 2023

Key Messages:

 - The low pressure system continues to rotate shower and
   thunderstorms through the area. Amounts look to begin to trend
   downward as we head through the overnight and into the day

 - Warmer and drier conditions move in for the end of the week and
   into the weekend.

Off and on showers have continued to rotate through the area today,
with hi-res guidance suggesting some increase in chances especially
across portions of southwest WI this late afternoon into the
evening. With model soundings suggesting limited instability, the
lightning risk remains a bit lower. A few showers continue to rotate
through the area overnight as the upper-level low makes its trek
eastward into Illinois. Hi-res guidance suggests a slow decreasing
trend in chances across much of the area, transitioning highest
chances to the east/southeast. Overall, the 26.12Z HREF 24-hr
probability-matched mean indicates areas of 0.01 to 0.25" with some
pockets of 0.5 to 1" (mainly in the south/southeast), with only a
few models suggesting low probabilities (around 10-20%) for
localized spots of greater than 1.5 to 2" by 12Z Wednesday.
Generally though, HREF shows highest amounts this evening with a
decreasing trend in rainfall amounts through the overnight hours.
Models hint at some potential for patchy fog development Wednesday
morning, so will continue to monitor trends and observations through
the night. The slow moving area of low pressure is expected to
continue its shift eastward towards the Ohio Valley through the day
Wednesday. Chances for scattered showers and perhaps a few
thunderstorms linger through the day, with rainfall amounts
continuing to lessen.

The low looks to finally lose its grip on the area with ridging
beginning to build eastward across the region Thursday. Overall,
global models seem to be in fairly good agreement with the general
upper level pattern for the end of the week and into the weekend,
with upper level troughing over the west and ridging over the east-
central CONUS.  Will note that a boundary setting up around northern
MN and waves of energy moving through the ridge may become the focus
for some showers and thunderstorms into the weekend. However,
guidance tends to lean towards keeping chances northwest of the
local forecast area. There is not a strong signal in the ECMWF
ensemble solutions right now, though an increase in GEFS solutions
showing more members in favor of any sort of rainfall potential has
been noted. For now, will stick with the current trends and maintain
the drier forecast through the weekend until details are more clear.
Small spread in guidance supports temperatures reaching into the
upper 70s to low 80s, which is about 10-15 degrees above normal.
Overall, this pattern looks to possibly bring much drier conditions
to the area along with an increasing trend in temperatures as we say
goodbye to September and head into the spooky season (October).


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 637 PM CDT Tue Sep 26 2023

Pockets of MVFR ceilings and visibility reductions (2-5 miles)
continue this evening with scattered showers moving from east to
west across southeast Minnesota. Lower MVFR/IFR ceilings take hold
as we move into the overnight hours with an isolated shower possible
at the TAF sites overnight. Ceilings remain MVFR/IFR Wednesday
morning with scattered showers returning to the forecast by mid to
late morning. Low confidence in the timing and location of showers
tomorrow so only a VCSH mention at this time.