Clayton, Iowa Weather Forecast Discussion

188
FXUS63 KARX 061037
AFDARX
Area Forecast Discussion
National Weather Service La Crosse WI
537 AM CDT Sat Sep 6 2025
.KEY MESSAGES...
- Scattered showers developing this afternoon (30-40% chance),
  especially north of I-90, before diminishing this evening.
- Remaining unseasonably cool this weekend. Maybe some patchy
  frost in spots tonight and Sunday night, depending on
  cloud/fog trends.
- Shower/storm chances return late Monday-Tuesday (50-60%), with
  much more seasonable September temperatures next week.
&&
.DISCUSSION...
Issued at 156 AM CDT Sat Sep 6 2025
Scattered showers (30-40% chance) this afternoon-evening:
Cool temperatures persist today with high temperatures likely a
smidge warmer than Friday, ranging from mid 50s to low 60s. A
potent shortwave trough will plunge into the Upper Midwest
today, dropping through the forecast area this afternoon. This
will coincide with favorable diurnal timing for steep lapse
rates to develop from the surface to at least 700mb, allowing
for 200-300 J/kg of 0-3km MUCAPE. Forecast soundings show the
depth of the saturated layer decreasing from north to south
across the forecast area, so scattered showers will likely be
most prevalent this afternoon north of I-90. Drier low levels
will be more of a limiting factor further south. Main timeframe
will be roughly 2-8pm, with activity diminishing quickly after
sunset. All in all, the setup for showers this afternoon looks
much more favorable than it was for Friday afternoon, but for
those areas that do get wet it should only amount to around
1/10" or less.
Patchy frost potential in some spots tonight and Sunday Night?
Attention then turns to low temperatures and potential patchy
frost development late tonight as skies clear out and winds die
off beneath a building surface ridge/high. There is some
question regarding potential late night development of fog or
low stratus particularly along and north of I-94, which should
preclude frost in those typical cold areas. Not all short-term
guidance supports this, but of the HREF ensemble members, both
the current and time-lagged HRW ARW and HRW NSSL members do, as
does the latest NAMnest. Our western counties, which will clear
out earliest and are unlikely to see any fog, may end up with
the most efficient radiational cooling. Later shifts will need
to assess tonight`s fog and frost potential, but for now low
temperatures in the upper 30s to lower 40s seem reasonable.
The surface high then shifts off to the southeast late Sunday,
which will initiate some weak warm advection over the area --
a trend that will continue into the new work week. Sunday night
therefore does not look to pose much threat for frost, but the
area to watch will be north of I-94 where skies will be clearest
and winds lightest.
Shower/storm chances later Monday-Tuesday, otherwise much more
seasonable temperatures:
As 500mb flow turns more zonal over the Midwest on Monday, moisture
return will increase over the Plains and eventually shift into
the Upper Midwest late Monday into Tuesday on a robust low level
jet. A shortwave trough looks to drop through the area Monday
night into Tuesday with an increasing likelihood (50-60+%
chance) for showers and storms. Ensemble guidance shows a large
spread in potential rainfall amounts from this system, with
10th-90th ranging from under 1/10 inch to greater than 1 inch,
so while confidence is increasing in rainfall potential,
rainfall amounts remain less certain. Amplified upper ridging
will progressively build into the region from Wednesday through
Friday, providing mainly dry conditions and much more seasonable
temperatures.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 537 AM CDT Sat Sep 6 2025
Main taf concern through the taf period is potential for showers to
impact the LSE/RST taf sites this afternoon/evening. Next wave
embedded in the northerly flow aloft will move across the Great
Lakes Region today into this evening. With daytime heating and lift
associated with the wave will allow for isolated to scattered
showers to develop across the area. Instability is very limited and
expect only an isolated storm or two. VFR conditions will prevail at
both RST/LSE taf sites through the taf period. However...if a
stronger shower impacts one of the taf sites...a brief period of
MVFR condition could occur. For now will introduce VCSH this
afternoon into the early evening hours based on coverage of the
showers. Another concern is the potential for fog development in
river valleys after 06z Sunday. An inversion develops
tonight...however a northerly wind above the surface may inhibit any
widespread fog development in river valleys. At this time will leave
out any mention of reduced visibility at the LSE taf site and keep
VFR conditions.
&&
.CLIMATE...
Issued at 156 AM CDT Sat Sep 6 2025
Record cool maximum temperatures for today and current forecast.
La Crosse, WI
Date           Record Cold High       Forecast High
-----           -----------            -----------
9/6              60F(1965)                63F
Rochester, MN
Date           Record Cold High       Forecast High
-----           -----------            -----------
9/6              58F(1965)                59F
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Kurz
AVIATION...DTJ
CLIMATE...Falkinham

NWS ARX Office Area Forecast Discussion