624
FXUS63 KDMX 131130
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
630 AM CDT Mon May 13 2024

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

.KEY MESSAGES...

* Showers and weak thunderstorms will continue through Monday across
  portions of central and southern Iowa. Some lingers SE into
  Tuesday. No real opportunity for strong/severe.

* Brief reprieve Tuesday into Wednesday before additional
  showers/thunder move through Wednesday PM into Thursday - Severe
  risk low.

* Cooler throughout the week - Highs mid 60s to mid 70s, lows
  mid 40s to 50s.

&&

.DISCUSSION...
Issued at 234 AM CDT Mon May 13 2024

Upper level trough continues to churn across western and central
Kansas early this morning, as seen on various GOES 16 water vapor
products, bringing with it increased lift and precipitation coverage
locally. Much of the precipitation to this point has been driven by
waves of low-mid level lift associated with theta-e advection. With
little to latch onto in terms of MUCAPE or wind profiles, activity
has been limited to periodic thunder and brief periods of moderate
rainfall. Greatest precipitation amounts have been along/south of
Interstate 80, with many a half inch or less. A hyper-local
precipitation max of around 3 inches has been seen just west of
Indianola, but came over the period of a few hours, limiting local
issues.

Showers and occasional thunder coverage is expected to increase
through the morning and into the afternoon as deeper lift associated
with the upper trough begins to move into the area. With its track
generally eastward and dry air encroaching from the north, there
will be a sharp gradient/cut-off to precipitation drifting southward
out of northern Iowa through the day. Weak SB/MUCAPE and muted flow
through the column (generally under 20 kts) will yield predominantly
light to moderate slow moving areas of showers/thunder. Hi-res/CAM
guidance suggests relatively widespread amounts of around 1 to 1.5
inches along/south of Interstate 80. Locally higher amounts for
areas that experience "stronger" convection and/or multiple rounds
of it may see totals in excess of 2 to 2.5 inches, with it occurring
over a number of hours though, hydrologic issues are not expected.
This activity may linger in southeast areas of the state into
Tuesday before briefly drying out.

Of casual note, there may be hints of smoke in the air at times
today across the state as northerly winds help usher in smoke from
Canadian wild fires. This is not expected to be highly impactful
aside from occasional smells or light haze with modeled near-surface
concentrations on the low end.

By Wednesday afternoon/evening, the next opportunity for showers and
storms will begin to move in as southern and northern stream
shortwave energy encroaches. Synoptic runs have continued the recent
trend of poor/no phasing of the waves, resulting in disjointed areas
of precipitation. For the most part, this continues to put Iowa
between the two shortwave paths and may only result in light
precipitation amounts. Regardless, the strong/severe threat remains
very low.

Deterministic guidance has come into better agreement on the large
scale pattern to end the week and into the weekend, but continue to
depict timing differences of passing compact shortwaves within.
Divergence then accelerates by Sunday. This continues to result in
prolonged low-end precipitation chances within NBM and the going
public forecast. At that time window, remarkably difficult to pin
down meaningful (and skillful) changes to PoPs.

Throughout the week, expect temperatures to be near-normal for the
most part with forecast highs ranging from the mid 60s to mid 70s.
The cool and generally wet conditions should continue to eat away at
lingering drought areas.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 626 AM CDT Mon May 13 2024

Conditions will range from predominantly VFR for northern sites
KFOD/KMCW/KALO to possible MVFR at KDSM to likely MVFR/IFR at
KOTM, driven by ceilings. Aside from KMCW, all other TAF sites
will battle at least some VCSH throughout the day, drying out
from NW to SE during the TAF period. TSRA potential is
relatively so, so have tried to limit mentions to most likely
windows. Have also kept ceilings broadly up compared to
guidance, with current observations higher than guidance
suggests in areas of eastern Nebraska and northwest Missouri.
Winds will settle northerly through the period, around 10 kts
or less.

&&

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

&&

$$

DISCUSSION...Curtis
AVIATION...Curtis