694
FXUS63 KDMX 231125
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
625 AM CDT Thu May 23 2024

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

.KEY MESSAGES...

- Another Round of Potential Severe Storms Late Tonight
- Quieter Weather Returns Friday Afternoon and Saturday
- Showers/Scattered Storms Sunday
- Lower Confidence Forecast Day7

&&

.DISCUSSION...
Issued at 335 AM CDT Thu May 23 2024

.Short Term /Today through Friday/...

Confidence Short Term:  Medium

Active pattern ramping up again late tonight into early Friday with
more severe potential overnight. Yesterdays storm now just southwest
of Hudson Bay with weak westerly flow and high pressure over Iowa
now at H850. Upstream already a rather potent spring system at H850
of 138dm is just entering northwest Wyoming. Farther south another
area of low pressure is located in New Mexico. Flow ahead of this
large western trough has turned back to the south over much of the
lower Mississippi River Valley at 00z with a plume of +5C dew points
already back into western Iowa; farther south +10C dew points are
into southeast Kansas and not far behind a pool of +15C dew points
extends across eastern Texas. Surface analysis at 04z shows low
pressure beginning to organize over western South Dakota and
Wyoming. Surface moisture return is slow, but dew points already in
the mid 50s have entered southeast Kansas. The synoptic models show
a double low structure approaching the Western Plains by 00z with
increasing southerly flow over Iowa. This will aid in advecting a
plume of 60 to 65F dew points into Iowa by 07z, focusing along a
cool front associated with the elongated trough as it crosses the
state. Instability will be ramping up through the late afternoon and
evening, though no real forcing mechanism will be available until
later in the evening as the trough/low approach. Today will see some
mid and higher level clouds in response to the approaching moisture
and warm air advection. Along with that, highs will likely reach the
upper 70s to lower 80s over the area. By tonight, 0-6km wind shear
will increase from 03z to 12z overnight to 35 to 50kts  with ample
MUCAPE of a conservative 500 to 1500 j/kg by 06z and continuing
through 12z. Though there are some differences in strength of both
thermal/forcing features between the NAM/Euro and GFS deterministic
runs at 00z, the HRRR is supportive of the NAM/Euro in that
convection is likely to break out in eastern/southeast Nebraska
between 00 and 06z and then quickly grow upscale into an MCS/MCV
bowing structure through Friday morning as it tracks east northeast.
Currently the GFS is slightly weaker than the NAM/Euro suite. With
support for decent H850 LLJ overnight and increasing shear aloft, we
will likely see a bowing QLCS potential with possible damaging wind
gusts and some brief tornados the main threats as the line tracks
east overnight. There appears to be a warm front moving northeast
with the warm air advection and this would be the likely axis of the
bowing feature as it matures overnight. There remains some
uncertainty as to how long the bowing structure will remain strong,
though QLCS features sometimes increase in strength toward dawn as
the H850 low level jet peaks. As for rainfall, PWATs are increasing
to 1.5 inches along the boundaries overnight with warm cloud depths
just above 10kft. This might lead to rainfall amounts up to 1.5 to
2.0 inches in a few spots, though the progressive nature of the line
should mitigate any widespread additional hydro issues. Right now
the 06z HRRR is showing the trailing southern edge of the QLCS along
US30 to I80 east of I35 may see between 1.5 to 2.0 inches in a 3 to
4 hour period. If this type of scenario sets up, will need to
monitor for some additional hydro issues during the event. As the
mesoscale feature exits by mid to late Friday morning, we should be
left with a relatively quiet afternoon through most of Saturday with
a break in the action until later Saturday evening. Weak high
pressure will build over the area Friday night into Saturday with
seasonal highs and slightly cooler overnight lows Friday night.
Highs tomorrow will reach the lower to mid 70s.


.Long Term /Friday Night through Wednesday/...

Confidence: Medium

As we approach Saturday night, another area of low pressure will
track into the Central Plains. The bulk of the energy is still
forecast by the medium range models to be just southeast of Iowa,
though the Euro does bring some slightly more unstable air into the
southeast/south by 12z Sunday. Though severe storms are not
expected, there may be a few stronger storms in far southeast and
southern Iowa. Rainfall may be the bigger issue, with another half
inch to inch across the south half of the state. Certainly not
needed at this time. Lows Saturday night will be in the  50s to
around 60 with highs Sunday in the 60s to lower 70s. As we round out
the weekend, there is lower confidence heading into Monday as
operational model runs diverge. The current EPS is more supportive
of the operation GFS with the light rain lingering Sunday night into
Monday over the region. This will likely keep the region cooler and
somewhat cloudy/wet with highs in the 60s to lower 70s again. From
Tuesday through Wednesday night, a break from the wet weather is
expected. Highs should gradually warm back to the mid to upper 70s.
By Thursday some scattered showers and storms are possible with
cooler highs in the lower to mid 70s. We may need to make some
temperature adjustments at that time.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 625 AM CDT Thu May 23 2024

Little to note until aft 06z when line of storms; possibly a
bowing structure with some severe potential moves east through
TAF network in Central Iowa by 12z. Most sites will see brief
period of storms and have attempted to time out the arrival.
Cigs generally VFR; except possibly during and aft storm
passage. VSBY also drops during storms. Wind expected to mix
today aft 18z for most sites; gusting to 20kts. /rev


&&

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

&&

$$

DISCUSSION...REV
AVIATION...REV