871
FXUS63 KDMX 262337
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
637 PM CDT Sun May 26 2024

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Some chances for showers and storms into Tuesday. A few
  stronger storms and gusty winds possible northeast Monday.

- Dry Wednesday, then chances for showers and storms return off
  and on later this week and into the weekend

- Fairly seasonal temperature regime continues

&&

.DISCUSSION...
Issued at 245 PM CDT Sun May 26 2024

Our weather pattern will remain somewhat active for the next
few days, albeit not to the extent as last week. After the
passage of Plains short waves to our south tonight, our weather
will be more influenced by the northern stream, and what will be
northwest flow behind a Great Lakes long wave trough. At onset
into tonight, have continued the mention of low chances
southwest per the latest mesoanalysis which shows uncapped ~1000
J/kg MLCAPEs south and west, and the latest RAP and HRRR still
hint at such development. The latest visible satellite trends
are uninspiring however, as is the surface moisture convergence, so
confidence in this occurrence is low. Any potential that there
is should end heading into mid-evening. The next concern would
be fog development overnight northeast where stratus continues
to linger late this afternoon, and temp/dewpoint spreads remain
5F or less. Although guidance doesn`t suggest much, this can be
a recipe for fog development, so have introduced patchy fog
wording for a start in those areas.

By tomorrow our attention will turn to the current MT short
wave as it reaches the Upper MS Valley by Memorial Day
afternoon. This will spread QG forcing mainly to our northeast,
but also modify the environment such that steep low level lapse
rates will be in place below 2km. This is expected to develop
scattered showers and storms over the northeast half of the
forecast area, and may result in some potential for somewhat stronger
convection with the potential for gusty winds with any
healthier cells. Soundings suggest gusts ~30 mph are possible
just due to mixing, with the potential for higher convective
gusts due to the steep lapse rates. 12Z HREF wind probabilities
suggest this as well with many members depicting wind potential.
The lack of adequate surface vorticity and boundaries may limit
the potential somewhat, but funnel clouds will be possible
northeast as well due to the proximity of the short wave and
200+ J/kg 0-3km CAPEs during peak heating and mixing. Machine
learning guidance from Nadocast also corroborates that potential
with small tornado probabilities. A bit farther south and west
the funnel environment would diminish with effective shear
rising to 40+ kts farther removed from the short wave, but this
would also result in a non-zero potential for some hail if
cells in the instability axis can tap that better deep shear.
This should all be diurnally driven, leading to dry conditions
later in the evening and overnight. Instability appears to be
more limited, but another short wave dropping into the Great
Lakes trough will introduce low chances for showers and a few
storms again into peak heating Tuesday, more driven by synoptic
lift in this instance.

We get a brief respite from precip chances midweek with surface
high pressure Wednesday and then upper level ridging into
Thursday. A central/northern Rockies long wave trough will begin
influencing our weather late in the week however with a few
short waves through its base Friday and Saturday. This will
reintroduce a few days with chances for showers and a few
storms. The severe weather potential appears low however based
on GEFS based CSU ML guidance, and deterministic GFS and EC
output both keeping any appreciable instability to our south and
west.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 634 PM CDT Sun May 26 2024

Lingering MVFR clouds in/around KMCW/KALO to start the TAF
period is expected to give way to VFR conditions returning prior
to 06z. Elsewhere, VFR conditions expected to prevail across
KFOD/KDSM/KOTM to begin the TAF period. A couple opportunities
for SHRA/VCSH and TSRA/VCTS move through during the latter half
of the TAF period, and have tried to target those windows. With
lesser confidence with the initial wave around/after 12z, have
gone with VCSH mentions. By the afternoon, confidence in thunder
is high enough that have entered VCTS at all TAF sites.

&&

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

&&

$$

DISCUSSION...Small
AVIATION...Curtis