850
FXUS63 KDMX 211718
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1118 AM CST Fri Feb 21 2025

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Moderating temperatures start today, leading into a prolonged
  stretch of warm, above normal temps next week

- Dry conditions through at least the weekend.

- Precipitation potential re-introduced next week with token
  sprinkles or light rain possible northeast late Monday, and
  then better chances midweek

&&

.DISCUSSION...
Issued at 531 AM CST Fri Feb 21 2025

One last morning of bitter cold today, but our pattern
transition toward warmer temperatures was already underway
aloft. Progressive northwest flow and rising heights were in
progress with a weak, moisture starved short wave from IA into
WI not even producing any clouds. Removing the stubborn dense,
cold Arctic surface high was more difficult however with a
sprawling 1040+ mb high still in place through the MO Valley.
Temperatures within this high were difficult to pin down
however. The latest RAP subjective analysis still showed the
925/850 mb thermal trough upstream across the MO Valley, but SW
500m winds were beginning to increase between the high and a
building lee side MSLP gradient with radiational cooling
conflicting with minor turbulent mixing. This resulted in temps
oscillating back and forth a bit but radiational cooling winning
out in the greater Nishnabotna Valley where mins had already
dipped to the teens below zero. Light or calm winds have mainly
kept wind chills above criteria, but winds may increase a bit
toward sunrise so will keep the current Cold Weather Advisory in
place with no changes. Winds will increase north later today,
with SW gusts 20-35 mph by mid afternoon.

The progressive northwest flow aloft will keep SW-W low level
flow in place through early next week with steadily rising
temperatures for several days resulting in highs in the teens
today, upper 20s/low 30s Sat, and what will be an extended run
of at least the 40s Sunday and likely 50s at times starting
Monday. The degree of warming is uncertain early next week
however due to influences from the snow pack as it begins
melting.

Regarding precipitation, a few weak short waves will traverse
the northwest flow through the weekend, but the first such wave
that may reintroduce precipitation into the forecast doesn`t
arrive until late Monday as it reaches the MO Valley late in the
day. The NBM doesn`t suggest PoPs into our forecast area,
likely due to its dry bias with low QPF events, however both the
00z EC and GFS deterministic and ensemble solutions suggest at
least some chances are needed so have introduced slight
chances/20% for measurable precip northeast Monday evening,
mainly due to mid level kinematic forcing ahead of a noted cold
front aloft.

There looks to be another precipitation window around midweek,
although confidence is reduced somewhat with run to run
differences from this time yesterday, especially with the ECMWF
in terms of system track and strength. However the EPS and GEFS
ensembles have been steadier highlighting the potential for
some rain, driven by a fairly mature system with deep, phased
kinematic and thermodynamic contributions, including
frontogenetical forcing along the cold front aloft. While
chances of measurable precipitation peak at 30-40% for any
particular 6 hr period due to timing uncertainties, 00z EPS and
GEFS peak 24 hr probabilities of measurable precip suggest 60+%
chances (likely) with the system. Rainfall potential looks
fairly minimal due to the system`s progressive nature and some
moisture limitation with both EPS and GEFS median 24 hr QPF
<0.10". A few rumbles of thunder are possible however with the
00z GFS noting some token CAPE aloft. Thursday looks dry behind
this system, with a bit cooler temps, but still remaining just
above normal for the end of the month.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1115 AM CST Fri Feb 21 2025

VFR conditions are forecast for the period. Breezy southwest
wind this afternoon may be gust at times, especially across
northern Iowa. The wind will diminish overnight and will be less
than 12 kts through the remainder of the forecast period. Any
passing cloud cover is expected to remain AOA 15 kft.

&&

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

&&

$$

DISCUSSION...Small
AVIATION...Donavon