Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 022342
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
642 PM CDT Sun Oct 2 2022

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

.DISCUSSION.../Tonight through Sunday/
Issued at 240 PM CDT Sun Oct 2 2022

Forecast Highlights:
--Generally quiet, dry conditions continue into Tuesday.
--Temperatures remaining pleasant, though slightly warmer, Mon-Tues.
--Still monitoring light rain chances late Tues through Wed.
--Much cooler to end work week.

Discussion:

REST OF TODAY THROUGH TUESDAY:
Forecast remains on repeat today. Scattered cloud cover in a push
of moisture brought a few sprinkles to portions of northern Iowa
again this morning but dry air in the low to mid levels has once
again limited us to anything more than these few sprinkles despite
radar returns suggesting otherwise this morning. A few additional
sprinkles will remain possible into this afternoon with otherwise
dry conditions persisting as the upper-level flow remains status
quo in the omega block today with a ridge over the central US
flanked by the low that continues to sit over the northern
Rockies, and the now- dissipating remnants of post-tropical
Cyclone Ian which have been absorbed into the mean upper-air flow.
The dissipating remnants of Ian are expected to merge with another
low pressure system today and then move just off shore in the
DE/VA/NC vicinity later tonight. This will allow for a slight
easterly shift of the central US ridge axis and the eastern US
trough which will in turn allow for some, albeit subtle, forward
movement of the northern Rockies low into tomorrow morning.
However, the low over the east coast looks to reorganize during
the day tomorrow and lag once again with the net result being an
increasingly positive tilted trough and ridge, with the ridge
axis shifting to be over the Great Lakes region by late tomorrow,
and additional forward movement of the northern Rockies low into
the western Northern Plains by roughly Tuesday morning.

With the ridge firmly in place until it starts to break down on
Tuesday, the surface high pressure over Great Lakes Region will
continue to dominate, shifting slightly southward as the ridge axis
tilts on Monday. This will keep southerly flow and some warm air
advection continuing to flow into the area leading to slightly
increased temperatures, especially over the western half of Iowa,
through Monday. The eastern half of the state will be closer to the
high pressure with winds taking on an easterly component at times.
These easterly winds will interrupt the warm air advection leading
to temperatures remaining more similar today through Monday over
eastern Iowa. Mid-level flow becomes south to southwesterly across
the area Monday night into Tuesday keeping low temperatures in the
50s and sending high temperatures across the area back into the mid
to upper 70s with increased warm air advection as the thermal ridge
nudges into the western half of the state. High temperatures in
portions of western Iowa, especially areas southwest, may climb back
into the low 80s on Tuesday if increasing cloud cover ahead of
the upper-level low can remain more scattered.

Increased mixing on Monday and again Tuesday will help enhance winds
slightly and likely decrease dew points by a few degrees. This will
send minimum relative humidity values to the 25 to 30 percent range
over western Iowa Monday and southern Iowa Tuesday which will help
enhance fire weather conditions somewhat, but still with a low
overall threat as fuels are not yet completely dry.

WEDNESDAY:
The upper level low/trough finally arrives in the region late
Tuesday into Wednesday bringing precipitation chances with it. These
will remain mainly north and west of the area before Tuesday evening
and then gradually dip southeast into Wednesday morning. Dry air
will continue to be a limiting factor with best chances for any
light precipitation over northwest Iowa and then potentially other
areas on Wednesday afternoon as the moisture catches up, but even
then, moisture looks unimpressive. May just end up with some clouds
and more sprinkles that could maybe give a few lucky locations a few
hundredths of an inch or so. Will continue to monitor the
precipitation chances on late Tuesday into Wednesday, but generally
not expecting any significant precipitation amounts.

THURSDAY AND BEYOND:
Another ridge builds over the western US behind the departing low
with northwest flow returning to the area and bringing some stark
changes on Thursday as a strong cold front pushes through the region
Wednesday into Thursday. Strong cold air advection behind the front
will send high temperatures falling into the mid 50s north on
Thursday with these 50 degree temperatures being felt area wide by
Friday. The cold front will also bring a strong pressure gradient to
the area on Thursday making for a brisk day with the colder
temperatures and northwest winds between 15 and 20 knots.

Dry conditions are expected to end the week as a large surface high
pressure moves back to the area into Friday which will bring the
return of a dry forecast to end the work week but will also help low
temperatures plummet with clear skies and lighter winds returning
frost/freeze concerns on Friday morning and again Saturday morning
as low temperatures fall back into the 30s.

&&

.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 640 PM CDT Sun Oct 2 2022

VFR conditions and south to southeast wind will persist through
the period. The wind may sustain at 12 kts or higher Monday
afternoon.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...KCM
AVIATION...Donavon


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