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088
FXUS63 KDMX 161720
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1220 PM CDT Mon Sep 16 2024

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Dry and warm today with highs in the mid to upper 80s

- Low potential for rain showers northwest Tuesday (<15%), otherwise
remaining dry and warm

- Multiple chances for precipitation by mid to late week

&&

.DISCUSSION...
Issued at 357 AM CDT Mon Sep 16 2024

Quiet conditions across Iowa early this morning, with nighttime
imagery showing areas of cloud cover across portions of eastern
Iowa, while the western half of the state sees clear skies. Light
surface southeast flow continues, along with early morning
temperatures in the mid 60s to low 70s. Analysis of the overall
weather pattern across the country has changed very little, with
upper level ridging remaining over portions of central into the
northeastern CONUS, while further west over California, a trough
continues to deepen, which will gradually shift north/northeast over
the next several days and bring multiple chances for rainfall.
Otherwise, today looks to remain dry with low level south/southwest
flow keeping above normal temperatures overhead as highs reach into
the mid to upper 80s. Tonight into Tuesday, models depict a frontal
boundary over Nebraska and South Dakota that looks to push into
portions of northwestern Iowa, with the majority of members keeping
conditions over the area dry due to dry air in the mid to low levels
as soundings indicate. However, if any showers were to overcome this
dry air, would see very minimal accumulations up to a few hundreds
by Tuesday afternoon. Temperatures reach into the mid to upper 80s
once again, with mostly clear skies.

By Wednesday, the aforementioned trough over California pivots
across the western CONUS and generally lifts northeast into the
western reaches of the Central Plains, with multiple shortwaves with
it developing showers and thunderstorms through the rest of the work
week. NAM and Euro guidance tracks the trough further north with a
slight retrograde westward by the late work week into Montana and
the Dakotas, keeping any boundary interactions at least into far
western Iowa. GFS guidance however has a more northeasterly trend in
this initial trough, though upper level ridging continues to win out
and keep precipitation chances primarily further west into Nebraska
and South Dakota where the better forcing seems to remain. However,
as the ridge gradually breaks down, precipitation chances become
more likely, specifically Friday into the weekend as another trough
per guidance looks to travel more eastward in motion, gradually
tracking directly over Iowa and bringing better moisture and forcing
mechanisms over the area to finally bring more appreciable rainfall
potential overhead. Not seeing a signal for potential severe weather
with the late week activity given lower end instability and shear
parameters, with the better potential looking to occur further north
and west at this time. Will be important to see how the earlier week
systems play out to gain more confidence in the expected impacts of
the later week activity, so will continue to monitor closely. After
several days of above average temperatures, values more in the
seasonal range look to arrive by the weekend, especially Sunday as
highs look to top out in the 70s.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
-- Changed Discussion --
Issued at 1219 PM CDT Mon Sep 16 2024

VFR conditions and south to southeast surface winds prevail
through the TAF period. Some pockets of shallow fog are possible
again toward the early morning hours Tuesday, however model
guidance has been less aggressive with fog development compared
to previous mornings. Thus opted to leave any fog mention out of
the forecast at this time.
-- End Changed Discussion --

&&

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

&&

$$

DISCUSSION...Bury
AVIATION...Martin