Johnston, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

153
FXUS63 KDMX 021129
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
629 AM CDT Wed Apr 2 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Storms exiting the area; becoming windy this afternoon.
- Brief break Thursday into early Friday
- Southern stream system brings more rain chances later
Friday/Saturday
- Return of pleasant and mainly drier weather Sun through
  Tuesday

&&

.DISCUSSION...
Issued at 310 AM CDT Wed Apr 2 2025

.Short Term /Today through Thursday/...

Confidence: Medium to High

Complex strong spring storm will be the focus for much of the
eastern half of the nation today, including Iowa. Convection
continues now over much of our area, having worked northeast out of
Missouri and Nebraska.  It appears to be weakening a bit with the
main area of storms that are moving into south/southeast Iowa at
730z. The surface lows over Kansas/Nebraska will consolidate into
one system by 18z over either north central or northwest Iowa.
Models are still having some differences even this late in the game.
The main result of this consolidation will be for the dry line
/occlusion to push most of the convection nearly out of the area by
14 to 15z in the southeast. We will briefly get into the warm sector
with the dryline passing through and this will allow for some
subsidence driven higher momentum air to mix down to the surface
during the late morning and afternoon hours. Gradient winds will be
nearing 30 mph at times as well. Wind gust potential is pretty
impressive with the GFS, while not as impressive with the EC. Opting
to issue the wind advisory for at least a period of 2 to 3 or 3 to 5
hours of stronger winds as the low reaches northern Iowa around 18z
through 01z. We will be outlooked in the east for some severe storms
today, though it looks like the bulk of any stronger storms will
exit this morning. We anticipate a possible SWODY1 update to the
areal coverage at 730am, possibly downplaying the extent west into
our area (of the southeast near OTM). Today will be rather warm
southeast/east as we briefly get into the warm sector. Highs will
remain in the upper 40s northwest to the mid 60s from Creston to Des
Moines to Waterloo. In the southeast, highs should manage the lower
70s for a few hours before most of us see cooler temperatures
building into the region this afternoon. Some deformation rain will
move over northwest sections late this morning/early afternoon as
the system pulls out.  Tonight the winds will diminish with
temperatures falling back to chilly overnight lows. We will fall
into the lower 30s north/northwest to the lower 40s in the
southeast.  Tomorrow, high pressure will provide us with a cool day
with clouds still present from the northern stream low and an
increase in clouds south due to the next southern stream system
building north for Friday. Highs tomorrow will remain in the upper
40s north to the mid to upper 50s south.

.Long Term /Thursday Night through Tuesday/...

Confidence: Medium to High

Clouds should overspread the region Thursday night into Friday as
some chances for light rain showers return to the region. Another
approaching front from the northwest will also add some lift for
additional showers into Friday night/early Saturday. Generally
speaking, most of the precipitation will be out of the region by
Saturday afternoon. We currently are modeling a slower exit and that
may need to be revisited. There will be little change to the airmass
over the region from Friday through Sunday.  Highs will remain near
normal with lows colder than normal. Saturday night will see mid 20s
northwest to the lower 30s south. Both medium range solutions now
support an additional push of colder air into early next week.
Despite sunshine, we may struggle to see highs climb out of the 40s
for Monday after another night of 20s through the state.  Tuesday
will see a slow moderation into midweek with slightly milder air
making its way east. At this point, any precipitation that occurs
with the advancing warm air advection is more likely to remain west
of our area. Highs Tuesday will move back to the mid to upper 50s.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 628 AM CDT Wed Apr 2 2025

Cigs and winds the main challenges today, though some lingering
showers/storms east and vsby will also come into play. Wind
gusts from east will give way to stronger southwest this
afternoon; possibly 25kt sustained gusting to over 40kt. Winds
lessen aft 00z. Most of the storms will be out of the region aft
17z at eastern sites ALO/OTM. /rev

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from noon today to 8 PM CDT this evening for
IAZ004>007-015>017-023>028-034>039-045>050-057>062-070>075-
081>086-092>097.

&&

$$

DISCUSSION...REV
AVIATION...REV