Mason City, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

353
FXUS63 KDMX 042041
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
341 PM CDT Sat Jul 4 2026

.KEY MESSAGES...

- Scattered thunderstorms remain possible into the overnight
  with the focus over north central Iowa.

- A few funnel clouds remain possible this afternoon. A
  localized damaging wind gusts and locally heavy rain may
  occur.

- Drier conditions to start the work week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 246 PM CDT Sat Jul 4 2026

Thunderstorms have developed along an instability ribbon over north
central Iowa this afternoon. Very weak surface flow combined with 0-
3 km CAPE values of 100+ J/kg has created a favorable environment
for vertical stretching of horizontal vortex tubes. This has led to
numerous reports of funnel clouds. The LCL levels are around 1000
meters or less and several funnels have been close to half way down
to the ground. There have been a report of at least one brief
tornado over northwest Iowa. These are landspouts and very weak and
form during the updraft phase of thunderstorm development. At the
current location of the storms, these will not be detectable on
radar other than the location of new updrafts. Otherwise, weak deep
layer flow has led to very slow storm motions leading to locally
heavy rainfall occurring under these storms. Already have measure
amounts exceeding 2 inches near Emmetsburg and Garner. Finally,
there remains the potential for damaging wind gusts remains with
very little deep layer shear present and a mid-level dry layer,
leading to wind development with collapsing storms. The hail threat
is low with vertically stacked storms and any ice falling through
heavy rain and undergoing substantial melting.

Water vapor imagery is showing short wave energy moving into central
South Dakota this afternoon. That may lead to additional
thunderstorm development later this afternoon and may help sustain
some convection into the overnight. An attendant damaging wind and
heavy rain threat will persist with any storms. Precipitation
chances will linger into Sunday mainly east of Interstate 35 with
generally dry conditions west as the short wave energy begins
to pass to the east.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 246 PM CDT Sat Jul 4 2026

Drier conditions are expected to start the week. The next short wave
arrives late Tuesday night into Wednesday and will bring
thunderstorm chances to northern Iowa. Westerly/zonal flow will
persist the rest of the week with another embedded short wave
passage around Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1245 PM CDT Sat Jul 4 2026

Mainly VFR conditions expected across the area outside of
thunderstorm locations. Expect thunderstorms to redevelop again
this afternoon with the focus over northern IA. Included Prob30
groups at most sites except KOTM this afternoon. Low chances
remain overnight but low enough chances to keep out of the
forecast. Light winds throughout except with some thunderstorm
outflow possible.

&&

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

&&

$$

SHORT TERM...Donavon
LONG TERM...Donavon
AVIATION...Donavon