450
FXUS63 KDMX 260439
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1139 PM CDT Tue Mar 25 2025

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- A quick round of light showers will bring brief gusty winds to
  portions of northern and eastern Iowa this evening.

- Shower and thunderstorm chances return from Wednesday night
  through Thursday night, with a Marginal risk (level 1 of 5) of
  hail Thursday night.

- Friday will be warm and windy, with near record highs around
  80 degrees and southwest winds gusting to near 40 mph at
  times.

- Additional precipitation is forecast this weekend into Monday,
  but confidence in timing and precipitation type is low at this
  range.

&&

.DISCUSSION...
Issued at 220 PM CDT Tue Mar 25 2025

It is a relatively active forecast period with multiple chances
for precipitation, including some wintry mix and some severe
thunderstorm potential, plus robust winds and near-record warmth
on Friday.

Currently skies are mostly sunny across Iowa with modest
northwest breezes around 5 to 10 mph in most areas. A subtle
shortwave impulse is moving south southeastward across Minnesota
and generating clouds there, with this feature expected to
translate and mature over about the northeast half of Iowa
around this evening, bringing a quick round of light showers to
that area and prompting 30-50% rain chances in the forecast.
Forecast soundings in our northeastern counties indicate deep
mixing up to around 700 mb this evening so brief gusty winds
will be possible with any showers that move through, but these
should be very transient.

The light showers will exit to our east after midnight tonight,
with a surface high pressure area building in and providing
mostly sunny and dry weather for most of Wednesday, with
temperatures again peaking in the mid 50s to lower 60s.
Meanwhile on Wednesday, a large thermal ridge will build over
the western U.S. and into the High Plains, but with a broad area
of surface low pressure forming around eastern Colorado. A warm
front will develop and extend eastward from this low across
Iowa and our service area from Wednesday night through Thursday
night, with periods of warm air advection aloft near and north
of the frontal zone generating rounds of showers and
thunderstorms during this period. Confidence in onset timing
and location of the rain is limited so POPs are only in the
20-30% range Wednesday night, but with forcing for ascent and
elevated instability increasing Thursday and Thursday night POPs
increase to 50-60% and some hail may even be possible around
Thursday night as stronger flow aloft/shear moves in and
intensifies elevated thunderstorms. The Storm Prediction Center
is appropriately messaging a Marginal (level 1 of 5) severe
weather risk for most of Iowa.

On Friday a broad 500 mb trough will move into the western U.S.,
shunting the preceding ridge southward and bringing our steering
flow out to west southwesterly. This in turn will push the warm
front northward into southern Minnesota, prompting much warmer
weather across Iowa during the day Friday. A moderate pressure
gradient and efficient mixing will promote breezy conditions,
with forecast soundings indicating top-of-ML winds around 35-40
KT for much of the day. Accordingly, have increased both
winds/gusts and temperatures/highs toward the NBM 90th
percentile on Friday, with near-record highs around 80 degrees
forecast and southwest winds of 20 to 25 mph gusting near 40 mph
at times. Dewpoints will be higher during this time however,
generally in the lower 50s or so, resulting in relative humidity
in the 45-60% range and mitigating fire weather concerns.

The aforementioned western U.S. 500 mb trough will be slow to
move eastward this weekend, with multiple waves ejecting out of
it and moving over Iowa between late Friday night and around
Monday of next week. This will result in several rounds of
potential precipitation, with the most likely coming in the
initial wave around Saturday and Saturday night. 60-80% POPs are
forecast during this time with some thunderstorm potential
initially but waning, and by Sunday and Sunday night some long-
range models indicate potential for snow or a wintry mix, but
there is significant variability in temperature solutions so
confidence in p-type is very low at that range.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1139 PM CDT Tue Mar 25 2025

VFR conditions and generally light winds through most of the
period. Another round of mid-level clouds and light showers
(PoPs 20 to 30%) overspread the area between 00 and 06z Thu. For
now have left out of package due to low probs. Light/var winds
swing around to the west and then south late in the period. /rev

&&

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

&&

$$

DISCUSSION...Lee
AVIATION...REV