Johnston, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

959
FXUS63 KDMX 060705
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
205 AM CDT Fri Jun 6 2025

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms later this
  afternoon into Friday with an additional round Saturday into
  Sunday. The severe potential through this period is low.

- Temperatures steadily in the mid to upper 70s through the end
  of the week and weekend.

&&

.UPDATE...
Issued at 205 AM CDT Fri Jun 6 2025

A few light showers have moved across about the northwestern
half of the forecast area overnight and should persist into the
morning, then decrease in coverage by this afternoon and
evening. More substantial POPs on Saturday as a surface low
moves across northern Missouri, but even then instability will
be limited over Iowa on the north side of the low, thus little
impact beyond rainy weather and isolated/scattered
thunderstorms with no severe weather expected. Have updated POP
timing trends and also lowered high temperatures Saturday to
account for cloud cover and rain. No other substantive changes
made to the forecast overnight.

&&

.DISCUSSION...
Issued at 219 PM CDT Thu Jun 5 2025

Leading precipitation from the approaching wave is just
reaching far western Iowa on radar this afternoon. So far this
is not yet reaching the ground, with model soundings showing
quite a bit of dry air to overcome and surface observations with
15-20 degree dewpoint depressions. With weak forcing and dry
air to overcome, precipitation will be fairly spotty and light
and this trend is reflected in CAM guidance. This regime will
continue through Friday with diurnal heating helping with some
spotty redevelopment in the afternoon. These will be widely
scattered and many locations will remain dry. Northern Iowa will
see the higher chances for activity with a modest increase in
forcing thanks to a weak embedded wave to the north. A secondary
weak embedded shortwave will pass across the area overnight
Friday into Saturday with continued chances for scattered
showers. Instability is very limited into the area with the gulf
cut off from the area so thunder chances area low, but a few
rumbles can`t be ruled out.

And finally by late Saturday into Sunday a more robust shortwave
will will dig across the northern plains and into the midwest. The
best forcing will move north of the area across Minnesota with a
trailing front that will pass across Iowa on Sunday morning. This
will bring the last chance for scattered showers to mainly northern
Iowa this weekend. The shortwave will also enhance the pressure
gradient across the area on Sunday with northwest winds
becoming breezy and gusting 20-30+ mph at times through the
afternoon. As the shortwave evolves into Monday model solutions
diverge, with the GFS favoring more wrap around precipitation
into northern Iowa with the Euro pulled further north.

The upcoming week starts off dry with temperatures gradually warming
thorugh the mid to upper 70s and into the low 80s by the middle of
the week. The next window for precipitation looks to arrive
with a late week system which will be better refined in the
days to come.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1042 PM CDT Thu Jun 5 2025

VFR conditions prevail with light showers continuing over
northern Iowa through the morning, mainly impacting KFOD and
KMCW. KALO, KDSM, and KOTM may see the occasional sprinkle
this morning as well, but impacts will be brief and minimal.
Winds will be light and variable through the period, with VFR
cloud cover in place through tomorrow evening.

&&

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

&&

$$

UPDATE...Lee
DISCUSSION...Hagenhoff
AVIATION...Dodson