National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KDMX 201714
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1214 PM CDT Sat Apr 20 2024

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Below normal temperatures today into tonight with widespread
  freezing conditions again tonight. Some warming begins Sunday.

- Scattered showers and a few storms Monday afternoon into the
  evening.

- More active late in the forecast period with increasing
  potential for showers and storms.

&&

.DISCUSSION...
Issued at 343 AM CDT Sat Apr 20 2024

Stratus has been trying to push into northern Iowa overnight but is
encountering much drier air across central Iowa with dissipation
along the southern periphery.  However, some moistening occurs into
the morning with clouds expanding into northern Iowa with a decent
cu field expected elsewhere.  Otherwise, broad northwest surface
flow persists through the day as thermal trof slides just northeast
of the forecast area with temperatures once again remaining below
normal given this setup.  Readings have gradually settled through
the 30s early this morning with most areas approaching 32 degrees,
therefore will leave freeze warning alone. Another repeat is
expected tonight with clear skies and weakening winds allowing a
decent radiational cooling event and freeze headlines appear likely
once again.

Weak warm advection begins by Sunday with winds a bit more settled
from the west northwest along with highs closer to normal.  The warm
advection intensifies into Sunday night and Monday ahead of a
shortwave dropping from Canada into the Midwest.  A surface boundary
passes into the state by the afternoon with a few showers and storms
developing in the narrow moisture corridor along the front.
Instability remains paltry with the limited moisture therefore
severe weather is not expected at this point.  Otherwise, cold
advection intensifies into Tuesday on the backside of the front as
the upper low slides just northeast of the state.  Steep mid level
lapse rates during the day on Tuesday may lead to some shower
activity in the north and east during the day as well.  Wednesday
appears quiet at this point with seasonably cool conditions.

The upper pattern undergoes transition toward the end of the work
week as upper troughing develops in the western United States.
Guidance continues to support an upper low passing from California
late Wednesday/early Thursday into the central US by Friday.
Moisture surges north ahead of this wave with as the Gulf of Mexico
is open for business and rapidly increasing instability and theta-e
advection into Iowa should lead to a decent threat of convection by
late Thursday/early Friday timeframe.  Still plenty of time to iron
out the details but this appears to be the opening act in a more
active period into the following weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1214 PM CDT Sat Apr 20 2024

Generally solid VFR OVC continues with a few breaks over the
northeast and far western areas of Iowa this afternoon. By late
afternoon, deck should become more cellular with a few more
breaks. Northwest winds gusting to near 30kts with mixing but
mainly northeast at KALO/MCW with lesser gusts through 00z
elsewhere. Aft 00z, back to CLR/VFR with light winds and less
mixing Sunday through 18z. /rev

&&

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

&&

$$

DISCUSSION...Cogil
AVIATION...REV