039
FXUS63 KDMX 261002
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
402 AM CST Thu Dec 26 2024

.KEY MESSAGES...

- Areas of dense fog and drizzle through this morning. Drizzle
  or light rain into this afternoon.

- Potential for more dense fog tonight and precipitation chances
  increase. Wet into Friday evening.

- Warm this weekend.

&&

.DISCUSSION...
Issued at 400 AM CST Thu Dec 26 2024

Low level moisture continues to slowly lift into Iowa early this
morning and is most evident over northern Iowa where temperatures
and dew points have been slowly rising towards 32 degrees.
Conditions have been more steady over central and south central iowa
with readings mainly in the mid 30s. This moisture which is
situated under an inversion located around 5 kft above the ground,
is resulting in widespread fog with much of it becoming dense along
and south of Highway 20. Therefore, have expanded the Dense Fog
Advisory north and west and will likely need to expand even more
this morning. The deeper low level moisture is over southeast Iowa
and some vertical ascent and resultant collision coalescence has led
to an area of drizzle to development over the southeast third of the
area including moving into the southeast portion of the Des Moines
metro. Temperatures and road temperatures are above freezing so not
expecting any icing.

The moisture advection will continue to move into Iowa today with
dew points gradually rising and this moisture will be driving the
high temperatures today. Have highs today near the NBM 25th
percentile and fairly close to the expected dew point values which
will rise through the 30s north and into the 40s south. A deepening
moisture profile may eventually lead to light rain as opposed to
drizzle especially by this afternoon and tonight. Overall the fog
conditions will improve diurnally today but some areas may be
shrouded in the fog with visibilities remaining below 1 mile at
times and it is possible that a time extension for the Dense Fog
Advisory is needed over parts of the area. The fog/dense fog is
expected to return tonight.

The precipitation chances will be maximized on Friday as the upper
level short wave arrives. Expect widespread rain/showers over the
state into Friday night. The moisture will begin to erode late
Friday night into Saturday and the precipitation will end. There is
a chance there could be a few peaks at the sun on Saturday after
several days socked in low stratus, fog and precipitation. Sunday
should also have some sunshine and will be warm with highs in the
40s and 50s.

The next system will arrive Monday and Monday night. Currently, the
progged setup is an upper level system arriving with surface
cyclogenesis occurring over Kansas and Oklahoma with the low then
moving east into Missouri. The upper level thermal profiles will be
cooling during this time but it does appear a surface warm layer
will hang around across Iowa that would result in any precipitation
beginning as rain. A transition to snow would occur from northwest
to southeast as the surface warm layer is eroded. Not many details
beyond that at this point and a lot can chance. Beyond that,
conditions are favorable for colder to perhaps much colder
temperatures to arrive by mid next week for New Years as the upper
flow becomes northerly though at this point this colder airmass does
not appear to have Arctic properties.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1141 PM CST Wed Dec 25 2024

LIFR/IFR ceilings and visibilities to prevail at all area
terminals through the period as persistent fetch of moisture
streams into the region. Have yet to see any -DZ in the state to
this point, although may still see some yet over the next few
hours. However, have opted to remove -DZ mention from the
terminals and confidence has decreased in it`s occurrence.
Temperatures continue to slowly climb across the region, now
right at 32F and 34F at MCW and ALO, respectively. Thus icing
potential will continue to lessen over the next several hours.
These LIFR/IFR conditions will persist into the day on Thursday,
with some minimal improvements by afternoon.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CST this morning for IAZ004-015-
023>028-033>039-044>050-057>062-071>075-082>086-094>097.

&&

$$

DISCUSSION...Donavon
AVIATION...Hahn

NWS DMX Office Area Forecast Discussion