-- Discussion containing changed information from previous version are highlighted. --
961
FXUS63 KARX 270408
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1108 PM CDT Thu Sep 26 2024

.KEY MESSAGES...

- Quiet weather continues through the short term. Favorable
  conditions for valley fog late tonight into Friday morning.

- Forecast remains dry (90-100%) through the weekend. Trends
  continue to indicate the mid-level low and remnants of
  Hurricane Helene remain southeast of the area with mid-level
  ridging influencing the Upper Mississippi River Valley.

- More seasonable temperatures expected next week.

&&

.DISCUSSION...
Issued at 138 PM CDT Thu Sep 26 2024

Quiet weather continues through the short term. Favorable
conditions for valley fog late tonight into Friday morning.

High pressure and mid-level ridging located over much of the
central United States will continue to influence the Upper
Mississippi River Valley this afternoon and overnight. Clear
skies and calm to light winds are expected through Friday as a
result of these features leading to another valley fog scenario
late tonight into Friday morning. Will need to continue to
monitor the trends for the potential for valley fog Friday
night into Saturday morning, as there will be a decreased depth
of the light wind layer as seen in RAP soundings. Overall, a
persistence forecast is the expectation in the short term.


Forecast remains dry (90-100%) through the weekend. Trends
continue to indicate the mid-level low and remnants of Hurricane
Helene remain southeast of the area with mid-level ridging
influencing the Upper Mississippi River Valley.

The aforementioned high pressure and mid-level ridging will
continue to influence the Upper Mississippi River Valley through
the weekend as a mid-level cutoff low centered over southern
Illinois slowly shifts eastward and merges with the remnants of
Hurricane Helene. The ECMWF Ens/GEFS/GEPS depict these features
remaining to the southeast of the region and continue to trend
towards a dry solution for the weekend with probabilities of
0-10%.


More seasonable temperatures expected next week.

Model guidance depicts a mid-level shortwave trough diving into
the region early next week. This trough is expected to drag a
cold front southeast through the area Monday night into Tuesday.
However, ample dry air in place over much of the region as well
as better dynamics across northern Minnesota and Wisconsin,
precipitation chances are only 0-15% during this timeframe with
Taylor County being the focus of the higher end chances. Cooler
air will succeed the front, allowing for more seasonable
temperatures into the middle of next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
-- Changed Discussion --
Issued at 1108 PM CDT Thu Sep 26 2024

Valley fog remains the main aviation concern with LIFR/IFR fog
and low-stratus at KLSE for the approaching morning hours.
Conditions appear to remain favorable for valley fog development
across much of the local area with a light wind layer to around
5-6kft in model soundings and falling dewpoint depressions.
Minimal cloud cover is expected through early morning, although
may need to watch if any cloud cover can sneak (10-20% chance)
from the southeast which may hinder fog development. Otherwise,
trends appear similar to previous nights with dewpoint
depressions at KLSE being 6 degrees F as of 27.03z. As a result,
have introduced a tempo for 1/4 SM at KLSE, favoring later into
the morning when considering potentially drier soils hindering
fog formation some and also seasonal climatology allowing fog to
linger later into the morning. After fog/low-stratus lifts, VFR
conditions are expected through the remainder of the TAF period
with some high clouds and generally light winds under 8 kts.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Falkinham
AVIATION...Naylor