Mason City, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

160
FXUS63 KDMX 280314
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1014 PM CDT Fri Jun 27 2025

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Low potential for storms far northeast Iowa Saturday morning

- Additional storm chances late Saturday into Sunday, with
  better chances Sunday afternoon and evening. Severe weather
  and locally heavy rainfall may be possible at times

- Warm conditions around 90 degrees this weekend with heat
  indices near 100 degrees west Saturday, then in the 80s next
  week

&&

.DISCUSSION...
Issued at 300 PM CDT Fri Jun 27 2025

Quiet weather persists this afternoon as weak high pressure remains
overhead, along with northwesterly flow keeping temperatures a bit
cooler. These cooler temperatures are also due to lingering low
scattered clouds over the northeastern half of the state this
afternoon, with current temperatures in the low to mid 70s northeast
and in the upper 70s to low 80s further southwest. Late tonight into
early Saturday, with a low level jet increasing over Nebraska into
South Dakota and a shortwave passing across Upper Midwest, this
looks to bring showers and storms at least back into the region.
HRRR and RAP guidance runs today continue to depict gradually
decaying showers and storms tracking out of the Dakotas through
southern Minnesota, just scraping into far northeastern Iowa around
sunrise and through the rest of the morning. However, the NAM keeps
this activity in southern Minnesota into western Wisconsin,
completely missing Iowa. Model soundings indicate that any storms
would be elevated in nature, with shear values around 20-25 knots,
though MLCAPE values are at least more favorable around 1500 J/kg.
Mid-level lapse rates look to top out around 7 J/kg, though with
fairly high freezing levels, would expect at most a very low
potential for small hail. However, damaging winds could be a threat
as DCAPE values around 1000J/kg Saturday morning. Overall, the
potential for severe weather looks low but a few storms could bring
sub-severe winds at most. Considering the track differences as
discussed above, impacts look to remain only confined far northeast
Iowa for potential sub-severe (at most) storms into mid morning as a
worst case scenario, but otherwise all areas remain dry for at least
much of the day.

A more defined mid-level shortwave passing through the Upper Midwest
by Saturday evening will be the next focus, with an increasing low
level jet into the area resulting in the development of a broader
area of showers and thunderstorms along a front over South Dakota
and Minnesota into northern Nebraska and continuing into Sunday
morning. Models are generally trending on keeping the bulk of
showers and storms into southern Minnesota, though Euro and NAM
guidance places some of this convection into northeast Iowa by early
Sunday, potentially skirting parts of far northern Iowa in the early
morning. A notable warm layer in the low levels would lead to
another potential for elevated convection, with favorable
instability, though limited shear into northern Iowa to really allow
for much organization to occur. A Marginal Risk for a few isolated
severe storms remains over northwest/northern Iowa to account for
the potential, with even a Slight Risk further northwest into SD/MN
where the parameter space is looking much better for severe weather
to be more likely. Beyond this morning activity, more scattered
showers and storms into Central Iowa are possible into Sunday
afternoon to evening as the system slides through the area, though
models are still struggling with the coverage of this activity. The
GFS and Euro depict scattered showers and thunderstorms across the
state, whereas the NAM has the bulk of activity in portions of
southern into eastern Iowa with the frontal passage. Sounding
guidance shows plenty of instability overhead with values generally
around 3000-4000 J/kg, with shear values around 30-35+ knots that
would allow for storms to develop and potentially bring a wind
threat given DCAPE values around 1000 J/kg given dry low levels and
potential some small hail. Warm cloud depths around 15kft with PWATS
over 1.5 inches will also introduce the potential for heavy rain as
well, as GEFS shows generally widespread 1 inch values, though
cannot rule out locally higher values. In terms of hydrologic
impacts, please refer to the hydro discussion for more details.
Details more specifically on severe weather potential and overall
expectations should be better known through the weekend as models
better capture this activity. Outside of on and off showers and
storm chances this weekend, returning southwest flow will increase
high temperatures back into the upper 80s to low 90s through the
weekend, with heat indices reaching near 100 degrees in portions of
western Iowa Saturday. Though not quite hitting Heat Advisory
criteria, heat impacts are still possible especially for more
sensitive populations, so proper heat safety should still be
practiced, especially if outdoor plans are in place.

Beyond Sunday, lingering showers and storms may continue into
Monday, followed by dry weather Tuesday and Wednesday before more
showers potentially return Thursday, with temperatures generally
topping out in the mid to upper 80s through the next work week. More
details on the forecast next week will be shared in the coming
days.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1014 PM CDT Fri Jun 27 2025

VFR conditions will prevail through the TAF period. There is a
low chance, around 20%, of thunderstorms affecting some
terminals early Saturday morning between about 08Z and 14Z.
However, given the low probability and confidence, have not
mentioned in the 06Z TAFs and will handle with amendments if any
impacts are foreseen.

&&

.HYDROLOGY...
Issued at 300 PM CDT Thu Jun 26 2025

The rainfall from yesterday afternoon into last night came in a
little lower than QPF, so overall the river forecasts were adjusted
downward accordingly. In fact the new river forecasts were low enough
that we were able to cancel some river flood watches because those
locations are no longer expected to reach or exceed flood stage.

Soil moisture remains high though across much of the CWA owing to
heavy rainfall over the past several days. NASA SPoRT soil moisture
percentiles for the top 40 cm of the soil (usually considered for
river forecasting purposes) are much above normal to near record
highs everywhere north of US 30, while there is a mix of near normal
to near record high values south of US 30. These above normal values
will tend to relax over the next several days in the absence of
heavy rainfall due to increased water demands from the ag crops in
place across the state, thus lessening additional flooding concerns.

Additional rainfall is forecast Sunday into Sunday night, however.
Right now the rainfall looks to be seasonally moderate. Latest tools
suggest this additional rainfall will have a minimal impact on
existing river trends especially at those locations where levels are
or will be running high. The rainfall may add minor amounts to the
crests but at this time no significant impacts are expected from
that rainfall.

&&

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

&&

$$

DISCUSSION...Bury
AVIATION...Lee
HYDROLOGY...Zogg