414
FXUS63 KDMX 050403
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1103 PM CDT Fri Apr 4 2025

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

.KEY MESSAGES...

- Light rain continues mainly southeast into the evening with
  some, but much lower chances farther north and west

- Dry Sat through Tue, but low chances (<=30%) return Tue night
  through Thu

- Cool temps to start the weekend, and again early next week.
  Widespread lows in the 20s Sat and Mon nights. Turning warmer
  for the middle to latter portions of next week

&&

.DISCUSSION...
Issued at 242 PM CDT Fri Apr 4 2025

Our current southwest flow aloft influences will soon give way
to a prolonged period of northwest flow to varied degrees with
the primary weather stories cooler temperatures and dry
conditions to start the next work week. The former effects are
still present however as noted 1-3km dry air from this morning
continues to erode and saturate farther into central and east
central IA. The rain is aided by strong, but departing
ageostrophic divergence in the right-entrance region of the
Upper MS Valley jet segment but mainly driven by relatively
higher based thermodynamic effects as the H85/H5 baroclinic zone
lifts into the Mid MS Valley. The rain isn`t expected to make
much more progression north and west as the H85/H7 theta-e
advection delivers only a glancing blow as it moves into MO and
IL by 00z ahead of its KC metro circulation at that level. Most
precipitation should end by later this evening, although
northern stream influences will sustain token chances for light
rain or sprinkles northwest ahead of the approaching ND PV
anomaly.

This PV trough will drive our transition to cooler temperatures
with a deep cold frontal passage early Saturday. This will
start a dry period into early next week with our attention
turning to cooler temperatures with brisk NW winds for a period
Saturday. Another strong PV trough will pass through the Great
Lakes early Monday with more brisk winds and cool high pressure
into the Upper MS Valley. While the forcing associated with this
wave is quite strong, it will be moisture starved and too far
removed to the northeast for any precip in IA. The main sensible
weather reflection will be below normal temperatures with
another cold frontal passage resulting in highs staying mainly
in the 40s Saturday and Monday, and widespread lows in the 20s
and freezing temps those following nights.

The next precip window appears to be toward the middle of next
week, but the timing and strength of the system are still
uncertain. The GFS suite appears to be a tad quicker, but both
the GFS and EPS model suites appear to be converging on the
solution with warm/theta-e advection starting late Tue and
kinematic effects lagged 6-18 hours behind a bit closer to the
surface features. This may result in a semi-extended period with
low chances for showers and possibly isolated thunder Tue night
into Thu depending on timing. This northwest flow pattern and
general Pacific origin of the waves for the midweek trough will
keep temps mild and above normal through the end of the period
(Fri).

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1103 PM CDT Fri Apr 4 2025

Clouds are widespread across the state, but are in the VFR
category to start the period. A period of MVFR ceilings lasting
6 to 8 hours at a given terminal will move across central
Iowa from around midnight to midday Saturday. There could be a 1
to 3 hour window of IFR ceilings with confidence highest over
northern Iowa with TEMPO groups elsewhere due to slightly lower
confidence in impacts. Winds from the north-northwest will
increase behind these clouds and stay brisk through much of
Saturday before diminishing Saturday evening. Wind gusts of 25
to 30 knots will be common.

&&

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

&&

$$

DISCUSSION...Small
AVIATION...Ansorge