000
FXUS63 KDMX 231138
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
638 AM CDT Tue Apr 23 2024

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

.KEY MESSAGES...

- Increasing shower activity with some thunder central and south
this morning

-Breezy NW winds today, with gusts up to 30-35 mph, especially east

-Increasing potential for much more active weather late week
 into the weekend, with severe weather and higher end rainfall
 on the table

&&

.DISCUSSION...
Issued at 412 AM CDT Tue Apr 23 2024

A bit active just south of the forecast area this morning as radar
depicts an area of rain showers and a few stronger storms in
Northern Missouri and Eastern Nebraska. Further north into Iowa,
radar returns are showing developing showers just pushing into
western Iowa, and are expected to fill in over portions of central
and across southern Iowa over the next few hours or so. This is in
association with a boundary that is draped across the southern
half of Iowa this morning, with the state sitting in between two
systems; the first circulating over the Upper Midwest, and the
other circulating over Kansas. Guidance generally has been
depicting increased moisture in the lower levels and good
forcing for lift in the midlevels. While instability is on the
weak side over the state, some thunder may occur as showers
continue to develop and track eastward across the state for the
rest of this morning. Overall rain totals are looking rather
minimal as conditions dry out this afternoon, with values
around or less than a tenth of an inch. The aforementioned low
pressure over the Upper Midwest region should push southeast,
with weak forcing allowing for a potential for some shower
activity over mainly far northeast Iowa into Wisconsin.
Temperatures have been much warmer tonight than earlier in the
week, thanks to remaining southwest flow across much of the
state, as values sit in the mid 40s to mid 50s. Temperatures are
expected to warm nicely with values in the 60s to low 70s.
However, as the system to the northeast departs, the flow
pattern will shift, becoming northwesterly as high pressure
approaches. Expecting increasing cold air advection as a result,
with decent mixing allowing for gusts to reach up to 30-35mph,
especially over northern Iowa. Cooler temperatures will follow
into the evening and overnight into Wednesday, with lows falling
into the upper 30s to low 40s, while the northern half of the
state sees values in the low to mid 30s. Isolated frost may
occur across the north with calmer conditions, though not
expecting any major impacts.

As the aforementioned high drops further across the region
Wednesday, dry and quiet weather is expected as cloud cover
decreases and winds remain light. Despite the cooler air mass
overhead, warming should be rather productive given the increased
sunshine, allowing for highs to reach into the 60s for most, and in
the 50s further northeast. High pressure departs Thursday, with
winds shifting southeasterly and increasing by late morning through
the afternoon ahead of the first of two major systems allowing for a
much more active period of weather to impact the state. The first
system of note will be in the form of a deepening trough becoming
negatively tilted as surface cyclogenesis occurs in the western
portion of the Central Plains. This with moderate theta-e advection
out of the south and increasing warm air advection over the state is
expected to allow for showers and storms to develop into Thursday
evening and continue into Friday. Model members seem to be in
somewhat better agreement on this timing of the initial wave of
precipitation, though the Euro slows the developing low and
delays the onset at least by 3-6 hours or so. Regardless, would
expect to mainly see elevated convection as a surface inversion
sets up over the area. The main issue seems to be lower end
shear values, though instability increases around 500-1000 J/kg,
which would likely lead to storms being really messy as they
struggle to maintain themselves. However, PWATS around an inch
with warm cloud depths around 12kft over the state look to allow
for a potential to receive appreciable rainfall, with totals
over an inch. In terms of possible severe weather, as the warm
sector lifts further into the state and instability increases
around 1000 J/kg, effective shear around 40 knots with steep
lapse rates looks to provide better support for more organized
convection into Friday afternoon/evening. PWATS with the
 moisture return overhead per soundings remain around an inch
which will likely allow for additional appreciable rainfall.

The second mentioned system overall looks very similar to the first,
though a bit stronger as a trough traveling out of the southwestern
CONUS develops a surface low that eventually lifts northeast into
the Central Plains by late Saturday into Sunday, though model
members have much more noticeable disagreement in terms of the
placement and strength of the low pressure system itself. Overall,
additional severe weather potential and additional appreciable
rainfall as the increased moisture out of the south streaming into
the region will allow for continued active weather. Will continue to
keep a close eye on these systems in the coming days as more data
becomes available. Outside of the severe weather potential late week
into the weekend, synoptic winds will be quite breezy through this
time period, especially Friday with values nearing headline
potential, which will be assessed over the next few days.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 638 AM CDT Tue Apr 23 2024

Scattered light rain showers are expected to continue this
morning, impacting mainly KDSM and KOTM through mid to late
morning before drying out. Ceilings are expected to remain VFR
throughout the period, with mainly mid-level clouds impacting
the terminals. This cloud cover is expected to decrease this
afternoon to evening across the state. Otherwise, winds will
increase out of the northwest later this morning through the
afternoon, with gusts up to 25-30 knots possible, highest over
the eastern terminals.

&&

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

&&

$$

DISCUSSION...Bury
AVIATION...Bury