Pleasant Hill, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

122
FXUS63 KDMX 131146
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
646 AM CDT Wed Aug 13 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

-  Patchy fog this morning.

-  High pressure will result in benign weather today into
   Thursday for most, with just a small, <20% chance, of
   decaying showers or storms northwest/north into early
   Thursday.

-  Warmer and more humid Friday into the weekend with heat
   indices nearing or exceeding 100 degrees again and a few
   periods of evening or nocturnal showers/thunderstorms.

&&

.UPDATE...
Issued at 307 AM CDT Wed Aug 13 2025

Few changes from previous/below. Fog this morning remains
exceptionally patchy and transient but have noted a few
observations under 1 mile at times. As temperatures continue to
cool towards the dew point temperatures, would expect fog to
expand in coverage into the morning hours with locally dense fog
possible, but likely will remain somewhat transient as has
occurred the past few mornings. Nonetheless, will continue to
monitor conditions closely for any SPS needs. Any fog will
dissipate within a few hours after sunrise.

Although CAMs would suggest two separate periods of decaying
showers tonight and again early Thursday mainly far northwest
to north, kept forecast dry for tonight as dry air looks to win
out per soundings, and as noted below. By early Thursday, the
moisture axis does start to nudge more into western Iowa which
may just allow for a couple showers/storms from the overnight
MCS over SD/NE to survive into the far west/northwest but are
still expected to be decaying and diminish with eastward extent.
Have expanded ever so slightly the low, less than 20%,
precipitation chances in our far northwest for this early
Thursday period.

&&

.DISCUSSION...
Issued at 228 PM CDT Tue Aug 12 2025

This Afternoon into Tonight...

Upper air analysis and water vapor imagery this afternoon is
depicting a seasonally strong upper trough north of MN, with an MCV
spinning across nrn MO. At the sfc, temps at 2pm have warmed into
the upper 70s and lower 80s, with Tds in the mid 60s northwest, to
the lower 70s central and south. A sfc boundary/wind shift
extends from southeast MN, swwd across n-central IA, and into
central NE. Convergence along this feature, combined with modest
instability /MLCAPE ~1000 J/kg/ is expected to trigger isolated
to widely scattered showers and thunderstorms from late this
afternoon into the early evening hours. Deep layer shear is
lacking, with 0-6km shear < 25kts, thus any updrafts/storms are
expected to struggle to organize, with pulsey type storms the
most likely storm mode. While the threat for severe weather is
very low, cannot completely rule out a stronger wind gust due to
drier air in mid-levels, especially as any cores collapse.
Storms should weaken pretty quickly after sunset, with loss of
diurnal heating.

Tonight, skies should gradually clear as sfc high pressure moves
into the region with temps cooling into the mid 50s to lower
60s, perhaps an opportunity to open those windows!  However,
with residual low level moisture and light winds, areas of fog
are expected develop once again. A few guidance tools /MOS and
HREF/ are showing the possibility for at least locally dense
fog, especially in the more fog prone areas such as river
valleys. As we know, fog forecasting is fickle, so at this point
will just highlight patchy fog in the forecast. Low confidence
on any headlines being needed, but will pass concerns on to
future shifts.

Wednesday through Thursday...

Sfc high pressure will reside over the region on Wednesday, with sfc
dewpoints a bit lower in the 60s.  Not exactly "delightful" on the
muggy meter, but a little better than the full on tropical values
we`ve seen much of July/August. Besides a few diurnal cumulus,
skies should remain sunny/mostly sunny with highs in the lower
80s. At this point, the HRRRSmoke is not depicting a major
amount of smoke to infiltrate the region, but will keep
monitoring this trend. Overall, should be rather pleasant late
summer day.

By Wednesday night and Thursday, the sfc high begins to retreat off
to the east, which will gradually turn winds back to the
south/southeast.  At upper levels a compact shortwave will move
across SD into MN, with a potent LLJ developing on Wednesday over
the central Plains. The various global models and their ensemble
counterparts are showing about a 20% chance of showers/storms over
portions of northern/northwestern IA on Wednesday night into
Thursday. Storm should diminish with ewd extent as they run into the
high and encounter drier air.


Extended Forecast...Friday into the Weekend.

Well...were not done with the summer pattern just yet as the
12.12Z guidance continues to show the upper ridge re-
establishing over the Corn Belt, with a series of low amplitude
shortwaves traversing the top of the ridge. With a southerly low
level flow becoming re-established expect temperatures to rise
again with 850mb temps rising into +20-25C range this weekend
into early next week. Highs on Friday through Monday will range
from upper 80s to low 90s, with sfc dewpoints surging back into
the sweaty 70-76F range. Heat indices will correspondingly rise
back to near 100F on Sat/Sun. There will be periodic chances
for mainly evening and nocturnal thunderstorms from Friday into
the weekend as the atmosphere becomes much more unstable. There
will likely be issues with capping /as H7 temps approach 12C/
so the LLJ will likely play a key role again. We`ll refine the
severe wx threat in the upcoming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 640 AM CDT Wed Aug 13 2025

Patchy fog and related visibility drops to start the period but
this fog is expected to dissipate within the next hour or so.
VFR conditions otherwise expected to prevail today with few
aviation concerns. Winds will be light and variable through the
period with mostly clear skies outside of a few diurnal cu.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...05
DISCUSSION...Fowle
AVIATION...05