647
FXUS63 KDMX 101113
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
613 AM CDT Thu Oct 10 2024

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

.KEY MESSAGES...

- Warm and dry conditions continue today, with wildfire smoke
  filtering sunshine overhead.

- Near record temperatures in southern and central Iowa on
  Friday. Slightly cooler temperatures further north.

- Cooling temperatures through the weekend and into next week,
  with potential for near freezing temperatures in the mornings
  next Monday through Wednesday.

&&

.DISCUSSION...
Issued at 344 AM CDT Thu Oct 10 2024

Clear skies and dry conditions have once again allowed temperatures
to drop quickly this morning, especially in low lying areas such as
the Nishna valleys where temperatures have already fallen into the
low to mid 40s as of this writing. Unlike yesterday morning where
radiational cooling was negated by light winds which persisted
through the night, calmer conditions tonight have allowed for more
efficient cooling. Of course, this comes to an end as the sun rises
and we see the thermal ridge to our west continue to build east,
bringing unseasonably high temperatures again today. As has been
mentioned in previous forecast cycles, smoke from the western US
wildfires will drift overhead today. This will lead to filtered
sunshine, and may have a slight effect on reaching max temperatures
today. However, this will likely only be on the magnitude of a
degree or two, so not much change to the forecasted highs for today.
It seems unlikely any daily records will be attained today, but
have kept mention in the climate section below for consistency.

These warmer temperatures continue for one more day on Friday, with
highs approaching the daily records at multiple sites in southern
and central Iowa. Further north, temperatures wont reach quite as
high due to a cold front slowly sagging into the state on Friday.
The location and timing of this front will play a role in high
temperatures on Friday, primarily in north central Iowa, but will
likely hold off until after peak heating for much of central and
southern Iowa. Through Friday evening, the front continues further
south into the state, bringing a slight cool down on Saturday,
albeit still with above-normal temperatures for much of the area
(normal values are generally in the mid 60s this time of year). The
front stalls near to just south of the Iowa/Missouri border, which
looks to keep temperatures a bit warmer there than further north. To
that same point, as a second and more amplified trough approaches
the area, models have started to depict a weak wave propagating
through the bases of the trough and along the boundary. With this
forcing and some very subtle moisture return from the gulf as
hurricane Milton departs east, some of guidance has started to
squeak out a little bit of precipitation in southeastern Iowa.
Despite this moisture return, the column still remains fairly dry
over our area, so not expecting to see much more than a few
sprinkles on Saturday, if anything at all. That being said, the
current trend is toward more moisture along the boundary on Saturday.

On Saturday night, the more prominent 500 hPa trough digs into the
region, bringing some gusty winds on Saturday night into Sunday and
a strong push of cooler air to start the week. There has been a
slight trend back toward warmer temperatures after forecasted highs
& lows plummeted with yesterdays guidance. This is primarily due to
the location of the trough now drifting a bit further east than
where it was yesterday, leading to slightly warmer 850 hPa
temperatures on the back edge of the trough. Depending on your
model, 850 hPa temperatures are now just slightly above 0 C (GFS) to
a few degrees below (ECMWF) across the area, with the coolest
temperatures being north and east. Ensemble probabilities have also
followed suit, now only showing a 15 to 25% chance of below freezing
temperatures roughly south of highway 30 and about a 40 to 50 %
chance north of highway 30 on Monday night/Tuesday morning. Either
way, the general signal for a significant cool down to start early
next week is still very much in play, so have retained the frost
mention in the grids for areas nearing freezing during the mornings
on Monday, Tuesday and Wednesday. As mentioned previous nights, we
are still multiple days out and will want to continue to watch how
the trough evolution effects temperatures in the coming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 610 AM CDT Thu Oct 10 2024

VFR conditions prevail through the period. Winds will be fairly
light this morning, and generally out of the east southeast.
However, as winds pick up through the morning, they will become
more southerly. Wildfire smoke is expected aloft again today,
but impacts to aviation are not expected.

&&

.CLIMATE...
Issued at 203 PM CDT Wed Oct 9 2024

Unseasonably warm temperatures on Thursday and Friday will
approach daily record values for sites across the area. Records
are included below for climatological reference.

Thursday, October 10 Daily High Records:

Des Moines:  88F (1962*)   Current Forecast: 83F
Waterloo:    89F (1928)    Current Forecast: 83F
Mason City:  87F (1928)    Current Forecast: 82F
Ottumwa:     89F (1930)    Current Forecast: 82F
Lamoni:      92F (1931)    Current Forecast: 81F

Friday, October 11 Daily High Records:

Des Moines:  86F (1962*)   Current Forecast: 86F
Waterloo:    90F (1920)    Current Forecast: 84F
Mason City:  85F (1928*)   Current Forecast: 79F
Ottumwa:     86F (1962)    Current Forecast: 86F
Lamoni:      84F (1962*)   Current Forecast: 84F

*Record occurred in multiple years

&&

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

&&

$$

DISCUSSION...Dodson
AVIATION...Dodson
CLIMATE...Dodson