Oskaloosa, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

373
FXUS63 KDMX 261133
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
633 AM CDT Tue May 26 2026

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

.KEY MESSAGES...

- Warm temperatures continue to start this week with highs in
  the mid 80s to near 90 today and Wednesday. Brief cooldown
  mid-week with highs still in the low 80s through end of week.

- Scattered shower and non-severe thunderstorms persist this
  morning. Additional shower and storm chances (20 to 30%) are
  expected late this afternoon into the evening and again late
  Wednesday into early Thursday, both over northern Iowa. The
  severe risk is low, but gusty winds and hail are possible.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 302 AM CDT Tue May 26 2026

Rain and thunderstorms continue over north central Iowa early this
morning, as a 30 kt low level jet noses up into the northwestern
corner of the state. The instability available to storms isn`t
overly high (~1000 J/kg) but has been enough for a few more
ambitious updrafts. However, the lack of any notable wind shear has
ultimately led to a quick demise of any of these stronger updrafts,
resulting in pulsey convection. Hail will be the primary threat with
these up then down storms through the morning, as well as gusty
winds around 30 to 40 mph as the stronger updrafts collapse on
themselves. The low level jet will likely keep scattered showers and
storms ongoing over north central Iowa through the morning hours,
with activity diminishing as the jet weakens after sunrise. The
potential for stronger updrafts (and associated impacts) will also
be waning through the morning as the available instability slowly
diminishes through the nighttime hours.

The conditions today and Wednesday generally remain status quo from
what we`ve seen over central Iowa the last few days, albeit with
more widespread temperatures in the upper 80s and not as breezy of
winds. As was pointed out in yesterday`s discussion, the 500 mb
pattern lacks any prominent features over Iowa through mid-week. At
500 mb, the midwest will be sandwiched between a broad cutoff low
developing off the west coast and persistent troughing to the
northeast, putting Iowa beneath a weak ridge. Through today and
Wednesday, this will keep the thermal ridge overhead and
temperatures warm. The stronger low- to mid- level jet from the last
few days will orient more over the plains ahead of the west coast
low, keeping that gulf moisture stream displaced to our west. The
rest of the moisture will be shunted south and east of Iowa by the
building trough to our northeast. That said, while new moisture
won`t be advecting in, residual moisture from the last few days will
remain pooled over Minnesota and northern Iowa. This residual
moisture will coincide with destabilizing environments both today
and Wednesday, leading to diurnally driven showers and thunderstorms
both days.

For today, convective initiation is expected over southern
Minnesota late this afternoon with an outflow boundary oozing
southward and kicking off additional rain/storms over northern
Iowa through the evening. The 0-6 km wind shear available to
storms this evening will be extremely low (less than 20 kts) but
the ~1500 J/kg of MUCAPE will be sufficient for at least a few
stronger updrafts. Like this morning, without any wind shear,
these stronger updrafts will quickly collapse in on themselves,
leading to pulsey convection. Because of this, the severe threat
will be low, although small hail and/or gusty outflow winds may
occur with collapsing updrafts. The storm prediction center
does have a marginal risk for severe weather (level 1 of 5) just
scraping our north, focused mainly where convective initiation
is expected in southern Minnesota.

This pocket of residual moisture generally remains through
Wednesday, albeit less robust compared to tonight. The moisture
pool will begin to push back southwestward into Iowa as high
pressure begins to build over the Great Lakes. As this occurs,
scattered showers and storms are once again forecast to develop
over Minnesota into northern Iowa late Wednesday afternoon into
the evening. Much like this morning and tonight, daytime
destabilization will boost instability values but shear will be
minimal. Therefore, expect similar storm characteristics to the
previous two rounds of scattered convection; pulsey storms
producing gusty winds and small hail, but with a low risk for
long-lived severe storms.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 226 PM CDT Mon May 25 2026

The upper air pattern is more pronounced to the west with a
level large cut-off upper level low that will be nearly
stationary and churn across the west coast most of the week. The
west edge of the flow around this trough will align well with
the gulf and pump moisture through the central plains. By late
week this unstable axis of moisture will shift ever so slightly
to the east, beginning to skim parts of southern and western
Iowa on Thursday. This may allow for a window of thunderstorm
activity into southern and western Iowa from Thursday into the
weekend. There is still no robust forcing mechanism so at this
time severe storms are unlikely. The main uncertainty is how far
this plume of instability will make it and how much of Iowa
will (or will not) be impacted.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 630 AM CDT Tue May 26 2026

Showers and occasional thunder linger over northern Iowa this
morning, primarily impacting KMCW. Current trajectory would
suggest this activity could reach KALO later this morning, but
expectation is for showers/storms to dissipate through the next
few hours, so have kept shower mention out of TAF for now.

Rain and clouds diminish north today, giving way to VFR
conditions and light southerly winds at all sites today. A few
showers/storms may develop over northern Iowa again tonight,
mainly near KMCW and KALO, but have kept PROB30 for SHRA and no
thunder mention due to uncertainty in exact timing and impacts.

&&

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

&&

$$

SHORT TERM...Dodson
LONG TERM...Hagenhoff
AVIATION...Dodson