524
FXUS63 KDMX 161720
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1220 PM CDT Wed Apr 16 2025

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

.KEY MESSAGES...

- Breezy with elevated fire weather concerns once again today
  into the early evening.

- Strong to a few severe storms Thursday evening with main
  severe threat from large hail.

- Cooler into the weekend, with another chance for precipitation
  Sunday into early Monday.

&&

.DISCUSSION...
Issued at 419 AM CDT Wed Apr 16 2025

Surface ridge has been sliding across Iowa overnight with light
winds and clear skies.  This has allowed temperatures to drop into
the 30s in most areas with a few upper 20s in favored valleys in the
north and west.  However, winds have been increasing from the east
southeast across the western half of Iowa during the early morning
hours as the pressure gradient begins tightening with the high
moving off to the east.  Relatively robust warm advection is
expected today with thermal ridging in the Plains expanding eastward
into Iowa.  The main concern focuses on elevated fire danger once
again, particularly in the north and west where winds are forecast
to be the strongest.  Increasing mixing with the strengthening
surface flow should keep dewpoints from climbing much during the
day.  Afternoon relative humidity values are forecast to drop to
between 20 to 30 percent, much like Tuesday with elevated fire
conditions across the west and north during the afternoon.  At this
point, have decided to issue an SPS and let the dayshift re-
evaluate later this morning on any changes to products.

Moisture/theta-e advection increases into tonight with an increasing
low level jet.  A few showers and storms become possible after
midnight as the moisture pushes into the state, mainly across the
southern half of the state. There will be some hail threat with
any of the stronger cells along with brief heavy downpours.
Otherwise, increased clouds and steady winds help to keep
temperatures much warmer tonight compared to current readings.
The chances for precipitation slide northward across the state
into Thursday morning as the best theta-e advection advances to
the north. As the precipitation exits to the north and east
during the day, a rather robust cap becomes established over
central Iowa by afternoon. Therefore, there is likely to be
several hours of no precipitation for much of central Iowa from
late morning into the afternoon with the cap in place. By late
afternoon, the boundary advances into northwest portions of the
forecast area with a triple point in far west central Iowa.
Sufficient forcing near this point and some weakening of the cap
should be enough for development in west central into
northwest/north central Iowa. At this point, the bulk of
convection appears to remain elevated, therefore the main threat
for severe weather would come from large hail. The convection
is expected to advance east across the area on Thursday evening
before departing to the east early Friday. Lingering showers
remain into Friday morning, mainly in the north but this
precipitation diminishes by midday with increasing subsidence
and cold advection during the day.

The late weekend system that was in decent agreement 24 hours ago
with regard to the deterministics now has significant differences.
The Euro has considerably more QPF than the GFS with the ensembles
only reinforcing the deterministic differences. Have continued
the likely PoPs on Sunday into early Monday given that at least
some precipitation should fall and adjust with upcoming cycles.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1220 PM CDT Wed Apr 16 2025

VFR conditions and gusty winds from the southeast will prevail
through the afternoon and into tonight. A band of low clouds is
forecast to develop with MVFR ceilings passing over most
terminals for a few hours Thursday morning. In addition, a few
showers or storms may try to develop towards and after sunrise
Thursday morning, but coverage and confidence are too low to
include any mention at this time.

&&

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

&&

$$

DISCUSSION...Cogil
AVIATION...Ansorge