316
FXUS63 KDMX 211132
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
532 AM CST Fri Nov 21 2025

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

.KEY MESSAGES...

- Patchy fog with more isolated areas of dense fog south until
  sunrise or slightly later.

- Rain possible along and just north of the Iowa/Missouri
  border later this morning to afternoon.

- Mild and pleasant conditions this weekend.

- Rain returns Monday, then trending colder through the end of
  next week.

&&

.UPDATE...
Issued at 344 AM CST Fri Nov 21 2025

Fog has once again developed into this morning, with the majority of
this fog occurring over portions of western and especially southern
Iowa, which is due to lingering low level saturation and light winds
overhead. Reports so far have generally been between 2-5 miles over
the majority of affected areas, with some periods of brief locally
dense fog over southern Iowa where values have fallen below a mile,
before improving again shortly after. Given the trends of
visibilities going up and down over the past few hours with this
fog, and guidance indicating little overall change in conditions
until at least around sunrise, the expectation is for these
conditions to remain, with some spots mainly seeing occasional brief
periods of dense fog, but otherwise patchy fog largely concentrated
south of I-80 until around or just after sunrise. An increase in
winds through the morning are expected to improve conditions across
the state. Close monitoring will remain on the conditions in case
the fog decides to overperform current expectations, which seems
unlikely at this time.

Beyond the fog, a look at satellite imagery shows north/northeast
Iowa under mostly clear skies, while high clouds cover the remainder
of the state while low stratus continues to slowly depart eastern
Iowa. Surface analysis further shows the features responsible for
these conditions, with a large area of high pressure centered over
the Dakotas into northwest Iowa, while just to the south, an area of
low pressure is centered over Kansas. A surface boundary in relation
to this low pressure system is draped west to east across northern
Missouri, with rain indicated per radar returns extending right
along the IA/MO border, though little if any of this is reaching the
surface. An elevated 850mb boundary is also present along the I-80
corridor, noticeable by northwesterly winds north of the boundary
and easterly/southeasterly flow to the south. The high pressure to
the north is still expected to slide southeast into Iowa today,
which will continue to bring the drier air with it into the state.
Models continue to show developing showers into southern Iowa later
this morning and remain into the early evening, with some increase
in mid-level moisture, but will be fighting the fairly significant
dry air near the surface with the aforementioned high pressure
largely taking over. Model soundings show this low level dry air
over much of the state, including into southern Iowa, which will
prove difficult to overcome. Therefore have continued to trend PoPs
low in central to south-central Iowa, with higher chances (40-60%)
in far southern Iowa where somewhat better chances for low level
moisture are expected by this afternoon. If any rain does occur,
accumulations are expected to be minimal along and just north of the
IA/MO border around a tenth or less. Otherwise, most areas will see
dry conditions with mostly cloudy skies, with highs expected to
remain cooler in the upper 40s.

Larger scale ridging primarily dominates the western to central
CONUS this weekend, which will result in relatively benign but
generally warmer conditions for Iowa, with dry air in place as high
pressure takes over. A weak wave quickly passing through the Upper
Midwest will drop a rather weak dry frontal passage across Iowa by
Saturday afternoon to evening, with little if any change in overall
conditions outside of shifting surface winds becoming northwesterly
into the evening. Otherwise, highs in the 50s are expected, so enjoy
it if possible. Into the end of the weekend into early next week, a
large trough tracking northeast out of the Desert Southwest is
forecast to arrive into the Central Plains, with increasing theta-e
advection into the state and forcing overhead that is expected to
introduce the next chance for precipitation by Monday. Temperatures
expected above freezing will result in any precipitation to fall as
rain, with widespread precipitation looking to occur later in the
morning to afternoon as saturation overhead really increases. There
are some notable differences between models, such as higher moisture
content and more favorable forcing per GFS, while the Euro is more
muted on both moisture and forcing, so will have to monitor trends
through the weekend. A shift to much cooler and breezy conditions is
still indicated in the long term models by midweek next week, which
are explained in further detail in the below discussion.

&&

.DISCUSSION...
Issued at 237 PM CST Thu Nov 20 2025

Mid and upper level clouds will begin to move in from the south
as a southern stream wave lifts toward the area. A fairly stout
stream of moisture will accompany this wave, but will meet the
cooler, drier air mass currently moving into the state. This
will limit rain chances in Iowa, as the drier mid-level air from
the north undercuts the saturated layer from the south. The net
result is a more southerly trend in precipitation chances, with
most of the rainfall on Friday being limited to areas along and
south of the Iowa/Missouri border. It`s possible light
rain/sprinkles squeeze through farther north into central Iowa,
but forecast soundings don`t look overly promising with the
stout dry layer around 925 mb to 850 mb. As a result, have
trimmed down the northern extent of precipitation chances on
Friday, but maintained the higher chances along the southern
border.

High pressure takes over on Saturday and skies finally begin to
clear out. Temperatures will be seasonably warm, with highs in the
mid to upper 50s on both Saturday and Sunday, making for a pleasant
fall weekend, especially for this late in November. You`ll
definitely want to take advantage of the mild weekend, because the
pattern takes a colder turn through next week. First, it looks like
another southern stream system will lift up toward the state on
Monday, bringing more rain chances to the area through the day. Once
this southern stream wave lifts, it will merge into the broader 500
mb pattern, ending our prolonged period of split flow. The northern
stream then takes over as the dominant pattern, allowing the a
canadian long-wave trough to dive southward into the central US
Tuesday into Wendesday. Cooler temperatures will be pulled down on
the backside of this system, dropping our temperatures considerably
through the second half of the week. Current 7-day forecast has
highs only reaching the mid to upper 30s Wednesday and Thursday,
although this will likely fluctuate through the coming days.

There has also been quite a bit of interest in precipitation
forecasts through Thanksgiving, particularly in terms of snow.
As of right now, there isn`t an overly consistent signal for
snow in the deterministic models. With the departing trough and
pockets of energy orbiting it, it`s not out of the realm of
possibility we could see some precipitation development through
the end of next week. Likewise, a transition to a more northwest
flow pattern opens up the possibility for subtle waves of
energy to kick off some precipitation. This potential for a more
agitated pattern combined with cooler temperatures certainly
opens up the possibility for snow. However, at this time range
and with such subtle features, it`s extremely difficult to
reliably forecast snowfall. Therefore, stay tuned to the
forecast through this weekend and into early next week, as
details around the Thanksgiving weekend become more clear.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 532 AM CST Fri Nov 21 2025

Conditions have improved this morning, as the fog has lifted and
low clouds have departed for the majority of sites with drier
air moving into the state. However, KOTM is still experiencing
IFR conditions with low ceilings and patchy fog. While the fog
is expected to improve in the next hour or so, clouds will
remain overhead, with light rain possible late in the morning
through the afternoon as a system passes through from the south,
while the rest of the terminals are expected to remain dry. VFR
conditions are expected for all sites later this afternoon to
evening, with skies gradually turning mostly clear. Light and
variable winds will turn more northeasterly to northerly today
before shifting southwesterly late in the period.

&&

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

&&

$$

UPDATE...Bury
DISCUSSION...Dodson
AVIATION...Bury