Marshalltown, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

823
FXUS63 KDMX 021959
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
259 PM CDT Wed Apr 2 2025

.KEY MESSAGES...

- Gusty winds persist this afternoon and evening, diminishing
  overnight.

- Mild and quiet conditions Thursday

- Light rain chances Friday into Saturday, then mild through the
  remainder of the weekend.

&&

.DISCUSSION...
Issued at 254 PM CDT Wed Apr 2 2025

Skies have cleared out nicely behind the morning showers and
storms, allowing temperatures to warm nicely ahead of the low
pressure passing overhead. This has resulted in cumulus
development throughout the area. Similarly, a few of these
rising parcels have taken advantage of a shallow layer of
instability within the warm sector, resulting in isolated
thunderstorms. The instability has been quite low (~500 J/kg),
but have seen some healthier updrafts thanks to the strong shear
through the unstable layer and even a splitting updraft, as was
suggested by the long straight hodographs. That all said, the
low CAPE/high shear setup has proved detrimental to the storms
longevity, as the strong wind fields shear apart the storms.
As of this writing, no reports have been sent with any storms,
with the storm chances diminishing through the next hour or so
as the low and associated boundary continue east through the
area.

In addition to the cumulus and isolated storms, the subsidence
being created by cold air advection and the tightening pressure
gradients around the low, have resulted in strong wind gusts
throughout central Iowa, with multiple observed gusts of 45 to
55+ mph. These winds have been strongest along the boundary,
but will likely still see breezy winds through much of the
afternoon and evening as the low continues eastward. The Wind
Advisory remains in effect until 7 pm, but will likely begin to
cancel counties from west to east as the wind threat diminishes
behind the boundary.

After the departure of the low pressure system, conditions
quiet down through Thursday as surface high pressure fills in.
This will result in light winds, mild temperatures and partly
cloudy skies with increasing cloud cover through the afternoon
and evening hours on Thursday. As we get into Thursday night and
Friday, another upper level wave will drop south out of Canada
and meet with the upper level ridging to our southeast. This
interaction of upper troughing to the north and ridging to the
south will be responsible for multiple days of severe weather
and heavy rainfall for those in the Ohio River valley region.
Fortunately for us, we will be displaced to the northwest of the
axis of heavy rainfall and storms, but will still see some
showers and occasional thunder sneak into Iowa on the far
northern periphery of the system to our southeast. Likewise,
ahead of the approaching upper level wave to our north,
additional rain chances will develop over northwest Iowa Friday.
Neither of these rain chances (north or south) will be overly
robust, given the main moisture stream will be to our south and
east. Precipitation chances in the northwest linger into Friday
night, and could even see a brief switch to a rain/snow mix in
the far northwest before ending early Saturday morning.
Precipitation chances with the southern system look to linger a
bit longer into Saturday, but will eventually drift south out of
the state through the afternoon.

In addition to precipitation chances, another shot of cool air
will funnel into the state with the aforementioned upper level
wave, keeping temperatures mild in the 50s through the remainder
of the weekend. As we move into late Sunday and Monday, yet
another reinforcing wave will eject through the overall
troughing pattern to our north, bringing another push of cooler
air on Monday, keeping temperatures in the 40s. While no
precipitation chances are in the forecast at this time, the 12z
GFS has started to produce light QPF over the northeastern half
of Iowa late Sunday night into Monday. The main gulf moisture
stream will still be off with the ridging to our southeast,
meaning any moisture would likely have to be sourced from the
pacific stream. This doesnt mean that precipitation is
impossible, but the profile may struggle to saturate without
sufficient moisture transport. This is evident in the rest of
the deterministic guidance, which only depict spotty QPF with
this wave, keeping most of our area dry. Regardless, will be
something to watch through the coming days. Beyond Monday, upper
ridging builds in from our west and temperatures begin to climb
again through the middle of next week. &&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1233 PM CDT Wed Apr 2 2025

Decent clearing has developed over much of central and southern
Iowa this afternoon, while MVFR to IFR clouds continue to impact
northern Iowa. Expecting these clouds to persist in northern
Iowa through the afternoon and evening, producing MVFR and
occasional IFR conditions at KFOD, KMCW, and KALO. Further
south, clear skies currently prevail, but MVFR cumulus clouds
have begun to stream in from the west, shortly impacting KDSM
and potentially KOTM later this evening. Finally, gusty winds
are expected through the afternoon, with gusts near or exceeding
40 kts at times.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM CDT this evening for As>007-
015>017-023>028-034>039-045>050-057>062-070>075-081>086-
092>097.

&&

$$

DISCUSSION...Dodson
AVIATION...Dodson