366
FXUS63 KDMX 150009
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
709 PM CDT Sat Sep 14 2024

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

.KEY MESSAGES...

- Low precipitation chances into Sunday night

- High temperatures 5-10 degrees above normal though Friday.

- Precipitation chances increase mid to late week.

&&

.DISCUSSION...
Issued at 232 PM CDT Sat Sep 14 2024

A pseudo Rex block is still ongoing over the eastern CONUS with an
upper highs pressure centered over the central Great Lakes and an
upper low (Francine remnants) slowly migrating south across the
lower Mississippi River valley. The large scale flow will begin to
evolve as an upper low over Saskatchewan and Manitoba gives the
upper high a nudge to the east going into Sunday. For Iowa though,
little change in the overall pattern through Tuesday then gradual
change by mid to late week.

A review of the upper level evolution this week mentioned above.
First across the eastern CONUS. The upper high is nudged east but as
this occurs, a non-tropical depression off the coast of the
Carolinas, will move eastward with the deepening upper level low
that will eventual ingest the remnants of Francine and become the
dominant feature. The system will encompass much of the eastern
CONUS by mid-week. Out west, another strong upper level system
diving south along the west coast followed by another system early
next week with result in a western trough. Tuesday night an upper
short wave lifting through the southwest flow will help shift the
weak ridging pattern over Iowa a bit east and will eventually lead to
precipitation chances to move in from the west.

Above normal temperatures with highs in the 80s through much of this
week and a few areas could touch 90 at times. Mostly dry conditions
are expected through Tuesday then the pattern will become more
active. Surface based instability does develop on Sunday though a
forcing mechanism will be lacking which will limit precipitation
chances. A fragment of Francine will break off and lift into Iowa
Sunday night but at that point, much of the instability will be
limited. The Gulf moisture stream into Iowa begins to reconnect mid-
week and should remain intact through the end of the week. This
combined with several shortwave fragments lifting into the area will
lead to increase precipitation chances.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 707 PM CDT Sat Sep 14 2024

VFR conditions were in place across central IA at 00Z with
patchy 4-6K ft ceilings and higher clouds east. These
conditions should persist into the night, but patchy fog may
develop across portions of northern IA starting 08-10Z with
MVFR/IFR conditions noted for the time being, although
confidence in degradation extent is low to medium. Confidence
increases that VFR conditions return later in the morning and
afternoon however. Additional cumulus development by afternoon
may lead to scattered weak convection, but confidence in
occurrence and location is insufficient to mention at this lead
time.

&&

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

&&

$$

DISCUSSION...Donavon
AVIATION...Small