524
FXUS63 KDMX 251140
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
640 AM CDT Sat May 25 2024

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

.KEY MESSAGES...

- Highs today once again in the 70s with rain and storms likely
  (>80%) tonight. Marginal risk in the southern half of the
  state for large hail and damaging winds.

- Rainfall amounts tonight totaling between 1 and 2 inches
  south with locally higher amounts possible. Confidence lower
  (20%) in flash flooding due to progressive storm motion.

- Additional rain chances Monday, but with light amounts. Rain
  will return next weekend.

&&

.DISCUSSION...
Issued at 329 AM CDT Sat May 25 2024

There was a noticeable dryness yesterday afternoon and overnight due
to the surface high moving across the Plains. 00z upper air analysis
showed the main low level moisture axis veered to the east with
the system that impacted the state on Friday. Some recovery
will occur as a wave moves off the Rockies today and pulls the
low level jet up into Nebraska during the day. An instability
axis will build into Iowa. CAMs have an MCS forming at the nose
of the jet later today over Nebraska, but its progression and
severity as it moves east has some questionable factors. Mainly,
the low will be positioned over Kansas and Nebraska and will be
pushed due east in the upper jet, keeping the brunt of
development south. Additionally, the speed of that upper jet
will make warm sector storms advance quickly to the east. This
may cut off the advancement of the instability axis further
north and cause the MCS to either decay or dive south.

All that being said, a pocket of MUCAPE values nearing 2000 J/kg
will focus over the southern half of the state and wane with time
tonight along with PWAT values around 1.5". Deep layer shear is
favorable for storm organization, particularly before midnight.
Plenty of synoptic energy at play to develop showers and storms over
the state. As long as the warm front stays in Missouri, storms in
the state would be elevated in nature with large hail and damaging
winds being possible, hence the Marginal Risk. The tornado threat is
negligible with elevated storms as well. Rest assured that winds and
hail will not be at the magnitude we saw Thursday night into early
Friday, justified mostly by the warm sector and brunt of the
kinematics being displaced to the south for places like Oklahoma.

We will see efficient rainfall out of this system, but with fast
storm motions limiting efficiency. Plenty of isentropic ascent over
the warm front. The CAPE profile is elongated with warm cloud depths
hovering around 10kft. Areas across the south can expect between 1
and 2 inches. The HREF PMM has a secondary swath of higher
precipitation amounts near the Highway 20 corridor, likely from
simulated decaying convective elements from Nebraska. Lower
confidence (~40%) in this secondary area of QPF at this time. The
aforementioned progressive nature of storms will spread the QPF over
6 hours and keep areas out of flash flooding troubles, but locally
higher amounts can lead to ponding and increased river levels,
especially for areas impacted the most from rains this week.

An upper level low in Canada will continue to churn additional waves
Sunday night as well as Monday, but with less and less moisture to
work with. One last wave comes through on Tuesday where the addition
of PoPs may be needed in further issuances. Otherwise, the upper
level trough will deepen over the northeast and build in by
midweek with high pressure settling in over the Plains. This
will block the Gulf from us until at least Friday, tempering our
rain chances. Highs will be near 80 for the week which is right
near average for this time of year.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 637 AM CDT Sat May 25 2024

VFR conditions expected for the daytime hours today with
generally southerly winds. Winds become southeasterly after 00z.
Showers and thunderstorms arrive after 06z tonight with MVFR and
IFR cigs and vsbys. Severe winds possible as storms reach KOTM.
Have added prevailing SHRA FM groups to reflect time of highest
confidence of storm arrival. Timing to be refined in future
issuances.

&&

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

&&

$$

DISCUSSION...Jimenez
AVIATION...Jimenez