627
FXUS63 KDMX 200854
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
354 AM CDT Sat Jul 20 2024

.KEY MESSAGES...

- Scattered showers with a few thunderstorms off and on through
  the weekend into early next week. Overall severe weather
  threat remains low, though a locally heavy downpour is
  possible.

- Continued mild through the weekend with highs in the 70s
  followed by gradual warming through the upcoming week.


&&

.DISCUSSION...
Issued at 350 AM CDT Sat Jul 20 2024

Overall pattern continues to feature an upper ridge over the western
U.S. and a closed low over Canada north of the Great Lakes with a
broad trough in between. This trough remains fairly stagnant through
about mid-week keeping off and on shower and storm chances in the
forecast today through about Wednesday.

A shortwave nudging into the region helped kick off precipitation
last night though amounts overall remain more minimal into the early
overnight hours through much of the area, a few hundredths to a
few tenths, as of 2AM. The exception is over southwest Iowa
where precipitation amounts and rates have been a bit higher
with amounts approaching 0.5 to 1" closer to the Omaha area.
This shortwave will be very slow moving today through Sunday as
it crosses into and through central Iowa. As a result, early day
scattered showers will continue to slide eastward through the
morning hours with additional widely scattered shower or storm
development this afternoon into evening. Forcing remains weak
with instability limited and shear minimal today thus making the
main hazard, if any storm can form, lightning or a localized
heavy downpour as otherwise any storm that does form will likely
be pulse storms, up and down quickly given the limited shear to
work with. Although uncertainty remains high in exact location
of showers/storms at any one time due to the scattered nature,
chances are highest over western into northern Iowa (roughly the
western third of the state) where HREF probabilities of 24-hour
QPF over 0.5" ending at 6Z Sunday are 40- 60%, with a few
localized higher values of 60-80%. Still can`t rule out funnel
cloud potential if any clearing can occur with the low coming
across the area providing good surface vorticity. 0-3km CAPE
looks to reach upwards of 100-200, depending on the model,
mainly over northern into western Iowa, however, NST (non-
supercell tornado) parameters in the NAM and GFS indicate
localized areas in parts of central to eastern Iowa as well. If
any activity does occur, it should be limited to peak heating
and dissipate by this evening.

As we get into tonight, some drying may occur. Given our overall
light winds which are expected to continue through Sunday, any
pockets of clearing could lead to some patchy fog potential,
especially north or west.

Scattered showers or a few storms will remain in the forecast on
Sunday, especially during the afternoon into early evening. Although
instability actually looks to be higher on Sunday, shear and forcing
continues to remain weak keeping storms generally non-severe, but
the funnel cloud potential will remain during peak heating on Sunday
and may even be higher than today.

Periodic shower/storm chances continue into mid-week with the
overall pattern remaining unchanged, as mentioned previously, and
weak impulses moving through the overarching flow at times.
Most of these chances Monday-Wednesday will remain diurnally
driven with the bulk of any shower/non-severe storm activity
during the afternoon to early evening.

Temperatures this weekend remain in the 70s with a slight warming
trend through the week with temperatures remaining in 80s, but
approaching the upper 80s to even the return of some 90s by next
Friday into Saturday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1152 PM CDT Fri Jul 19 2024

Scattered light showers are around KDSM/KFOD currently and will
be in the vicinity early in the period. Cigs will gradually
decrease later tonight and into Saturday and there will be a
period of MVFR at times near at all sites except KOTM and could
have locally IFR near KFOD. Conditions will gradually improve
later in the afternoon and into the evening. Light winds will
continue and be 8 kts or less.

&&

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

&&

$$

DISCUSSION...KCM
AVIATION...Donavon