788
FXUS63 KDMX 180452
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1152 PM CDT Mon Jun 17 2024

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Slight Risk of severe weather this afternoon. Damaging winds,
  hail and heavy rain the primary threats.

- Additional severe weather chances return late Tuesday.
  Damaging winds and heavy rain are the primary threats early
  on. Heavy rain to persist Tuesday night and into Wednesday.
  Highest amounts in the west.

- Wet pattern remains nearby until the weekend.

&&

.DISCUSSION...
Issued at 255 PM CDT Mon Jun 17 2024

Afternoon surface analysis placed the boundary diagonally across
central Iowa with a slow descent northward. HCR can be seen ahead of
it in the uncapped warm sector that has 1500 J/kg of MUCAPE. Models
overnight have trended H70 temperatures cooler across the state
today with the EML reaching the MO river by the end of the day. This
opens up the possibility for some thunderstorms to form along the
aforementioned boundary this afternoon across the northern part
of the state. Chances of storms are higher on the eastern part
of the boundary where the H70 temps are cooler. As for severe
weather, better deep layer shear values near 50kts can be found
in the northwest. If storms can get going in this area, wind and
hail will be possible. With moisture pooling along the
boundary, cannot entirely rule out a tornado right along it, but
the chances are low. A sustainable updraft could become
supercellular in the better shear (also generally where the
Slight Risk is). Storms further to the south and east and away
from the better shear will likely pulse up and down, but still
have the potential for hail and a strong wind gust. High
temperatures have trended down with the cloud cover and cold
pool in the north today with highs being held in the 80s
northwest and near 90 southeast. The hindered mixing from the
cold pool has kept wind gusts relatively tame, but 35 mph gusts
will be more apparent in the west before sundown.


The front will lift into Minnesota tonight and keep much of the rain
to the north of the state tonight. Early morning stratus appears
possible for Tuesday morning as moisture continues to pile in from
the south. This will also limit high temperatures. Winds early
in the morning could be gusty in the west due to the nocturnal
jet. Before that eases, 40kt gusts could be measured in the
west. Clouds will start to erode in the southeast for the
afternoon, but will be short lived as the trailing cold front
from the nearby surface low approaches. CAPE values will recover
into the 1000s in the far west with 0-3km shear values near
30kts. Storms will evolve into more of a heavy rain threat early
on as the poor orientation of the line relative to the shear.
The mean wind will be parallel to the boundary, generating
training storms. 13kft of war cloud depths, PWATs exceeding 2
inches and a saturated profile all point towards heavy rain for
the west once again Tuesday night. what could further exacerbate
the setup is the timing of the front stalling as the upper
level ridge builds in from the southeast. Currently the HREF
LPMM for tomorrow night has widespread rainfall values exceeding
an inch with localized areas receiving 3"+. What may spare the
state from further rain is the lee cyclone that forms late
Tuesday with moisture becoming trapped along its warm front in
Kansas, disintegrating much of the rainfall further north. At
least localized impacts from water are possible in the west.
Will continue to monitor trends in upcoming issuances.

The front will advance as far as southeast Iowa Wednesday, but
retreat back northwest with time, brining more rain to at least
northwest Iowa and Minnesota Wednesday night. That same front will
stall somewhere very nearby for the remainder of the week, hence the
continual rain mentions for at least the north. Current ensemble
guidance keeps the axis of highest cumulative precipitation for
the entire week in Minnesota, but a healthy amount of rain can
still be expected for at least the northern and western part of
the state by the end of the week. An upper level closed low is
anticipated to arrive this weekend, giving us another chance of
more organized precipitation, but also shoving the upper level
ridge into the Atlantic and building another one over the Desert
Southwest, bringing a foreseeable end to the Gulf moisture
channel to the upper Midwest.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1140 PM CDT Mon Jun 17 2024

VFR conditions are expected to prevail through the night, before
low cloud cover develops in the morning hours. These may lead
to a brief periods of MVFR conditions. Gusty winds also pick up
in the morning hours, with gusts up to 30 to 35 kts possible
through the day. Cloud cover will continue to increase through
the day, with showers and thunderstorms becoming likely in the
evening and overnight hours, especially at KFOD, KMCW, and
KDSM. Thunder will be possible during this period, but will be
better refined in future TAF issuances.

&&

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

&&

$$

DISCUSSION...Jimenez
AVIATION...Dodson