927
FXUS63 KDMX 230911
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
311 AM CST Sat Nov 23 2024

.KEY MESSAGES...

- Seasonably mild weekend with highs approaching 50 in some spots.

- Cloudiness, cold temperatures make a return Monday. Confidence
  in precipitation still too low in both time and location(~15%
  confidence)

- Low confidence (~20%) in precipitation potential for the
  midweek. Continue to monitor the forecast.

- High confidence (90%) in highs in the 30s next week. High
  confidence (80%) in below normal temperatures after
  Thanksgiving.

&&

.DISCUSSION...
Issued at 300 AM CST Sat Nov 23 2024

Overnight objective analysis illustrated lee side troughing taking
place over the Rocky Mountain range in Colorado. A low-level
ridge axis will move across the state through this afternoon and
usher in southerly flow and WAA. Meanwhile, the Pacific
moisture plume to our northwest will help generate some midlevel
cloudiness in the north. Combine these factors and you have
another tricky high temperature forecast for the day. Have made
some minor adjustments to the north and east where clouds are
most likely to reside today, holding these areas in the 40s for
the day. The southwest will receive more sunshine today and
approach the 50 degree mark this afternoon. The sustained
southerly flow with elevated winds tonight will keep lows
generally above freezing and fog out of the picture for most of
the area.

The aforementioned cyclone will be deepened by an upper level
disturbance that will be intensifying overhead through Monday. The
initial weather response to this system will be the buildup of
stratus once again, especially nearest the low center in the south
and southeast. Expect these clouds to become increasingly present
beginning late Sunday into Sunday night. Temperatures may suffer
some from the clouds, but highs will be in the 50s across the
south. Some areas near the southern state line may reach 60
degrees. This will also be the final mild day in the
foreseeable future, more on temperatures in the moment. Models
aren`t in perfect agreement yet on how the moisture will be
handled by this system as well as by another wave that will come
into play on Monday. What can be said with certainty is the
bulk of precipitation will be southeast of the state. The
prediction mentioned in the previous discussion holds true in
this issuance: inconsequential drizzle/light rain would be the
most likely outcome for the area. Depending on what low level
moisture remains for the secondary system, there could be an
additional chance at seeing rain/snow in the far north, but dry
air present in soundings leads to the belief that amounts would
remain light (~0.01").

Now for temperatures: it`s gonna get chilly out there this week!
H850 temperatures below 0C settle across the state Monday and don`t
appear to vacate for the remainder of the period. Highs will be in
the 30s for most of the week and plummet into the 20s for next
weekend once a series of systems passes by. We are continuing to see the beginning
of December trend colder. An upper-level low will close off and
park somewhere near the southeast coast of Canada. This locks in
northwest flow over Iowa and means that CAA will continue to usher
in an airmass fitting for the start of meteorological winter.
Notice the single digit lows for the north near the end of the weekend.
The cold will continue into the beginning of the following week.

Regarding the midweek systems: the previous discussion correctly
describes the weather for Wednesday and Thursday as highly
uncertain, owed to how models are handling 3 separate waves
propagating in the upper air pattern at that time. A strong jet
containing a plume of Pacific moisture will be set up across
the Mid South, which leads to increased confidence that the
southern-most wave should dominate the other two. The current
precipitation chances illustrate this idea well, keeping the
bulk of precipitation in Missouri. This doesn`t completely
eliminate rain/snow chances for Iowa over the holiday so
continue to monitor forecast trends this week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1053 PM CST Fri Nov 22 2024

Fog potential, timing, and coverage continues to be the primary
concern for terminals overnight. At issuance time, sharp west
edge of 700-1100ft AGL stratus extends from just east of MCW
south to near TNU to just west of OTM. VFR and high clouds were
evident west of this line. Latest model output suggests gradual
movement east through the period, resulting in high-confidence
that stratus persists east. The fog potential & uncertainty
arises just to the west of this sharp stratus back-edge where
lessening winds beneath the surface high pressure will combine
with dew point depressions that were already in the 3-8 degree
range at issuance time. So confidence is high in patchy fog
formation, however areal extent and timing remain uncertain,
especially given increasing high-level clouds. As of now, HREF
depict highest probs from MCW to DSM to OTM, so have added
mention into those terminals. Will also add to ALO for a period
as HREF data points to elevated probs. FOD should be far enough
west & more influenced by drier air and thicker high clouds.
Trends will need to be monitored closely. Expect conditions to
VFR everywhere by late morning and thru the rest of the period.

&&

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

&&

$$

DISCUSSION...Jimenez
AVIATION...Hahn