863
FXUS63 KDMX 010436
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1136 PM CDT Fri May 31 2024

 ...Updated for the 06z Aviation Discussion...

.KEY MESSAGES...

- Showers and storms focused mainly west/north through AM Sat
  Brief heavy rainfall possible through evening north/northwest
- Break Sat through Midday Sunday
- Mon/Tue systems a bit stronger with potential heavy rainfall
  and some severe storms by Tuesday afternoon/evening

&&

.DISCUSSION...
Issued at 122 PM CDT Fri May 31 2024

.Short Term /Tonight through Saturday Night/...

Confidence Short Term:  Medium

Main concern this period will be the chances for storms over the
area next 24 hours. We continue with a weakly forced synoptic
pattern and cool front northwest with an upper level wave and old
MCV tracking through the region today into tonight. The old MCV has
been moving north into northern Iowa this morning which the upper
level wave is likely beginning to enhance some of the convection
over the western counties late this morning. An upper level ridge
has kept H700 steering currents from the southeast over southwest
Iowa, then recurving northeast over western to northeast Iowa. The
ridge has managed and will maintain an area of lesser PoP chances
east and southeast through this evening. We have warmed more rapidly
over the southeast/central due to the ridge and highs should breach
the 80 degree mark this afternoon there. Aloft at H850, a ribbon of
deeper moisture extends from western Iowa into Central Nebraska
south into the Southern Plains and Gulf Coast States. An area of low
pressure over northeast Texas will move east northeast tonight,
pulling the weak boundary over northwest Iowa east tonight as well.
This will enhance showers and storm coverage over the west and
northwest this evening and overnight. Across central to southeast
and eastern Iowa, forcing remains weaker and coverage of showers and
storms in these areas will be less. With the activity being mainly
instability driven, severe chances remain rather low. Shear is not
anticipated to increase through the event tonight and Saturday
morning. Overnight tonight, we will remain quite mild with lows in
the 60s across the region. Although there may be a few lingering
showers early tomorrow morning, the bulk of the day will be pleasant
with partly cloudy conditions and highs climbing back to the upper
70s to lower 80s. Saturday night will remain rain free with some
clouds returning to the west/northwest ahead of the next upstream
wave tracking into the Northern Plains, while another system
develops in the lee of the Rockies in the Southern Plains by Monday.

.Long Term /Sunday through Friday/...

Confidence: Medium

There continue some timing differences with the system on Sunday,
but the consensus is for some storm development west of I35 during
the afternoon/evening with the bulk of any storms arriving overnight
into early Monday morning as an upper level short wave and pulse of
warm air advection moves over the region Sunday night. Wind shear
remains rather meager Sunday night into Monday, but there will still
be some need to monitor the storms overnight due to storm motion.
Some storms may backbuild across the area Sunday night. As PWATs
increase to 1.5 to 1.75 and warm cloud depths reach 3km, locally
heavy rainfall will become more likely east of I35 after midnight as
a trough/weak boundary moves east into eastern Iowa. Rainfall totals
could reach 2 to 3 inches in some areas in this scenario and will
need to be monitored in later forecasts. After highs in the upper
70s to lower 80s Sunday, Sunday night will be mild and rather humid,
with overnight mins in the mid to upper 60s. By Monday morning, we
should be entering a brief break in the activity until later Monday
afternoon or evening. The main upper level trough will still be west
of Iowa Monday morning, but finally drive east through the region by
Monday night into Tuesday. Highs Monday will reach the upper 70s to
mid 80s.  Both later Monday into Tuesday appear active with showers
and storms and the potential for locally heavy rainfall, though
Tuesday evening appears to be the timeframe of higher severe
potential as shear increases through the column. The GEFS mean
rainfall Monday/Tues is running 1 to 1.5 inches while the EPS mean
is running about 1 inch at this time. Once the trough exits on
Tuesday, the remainder of the period will be less active with a
return of west northwest flow and gradually cooler temperatures. By
Thursday and Friday, H850 temps fall to about 9C northeast to 13C
southeast. This should bring highs back down to the 70s northeast to
the lower 80s southwest with relative comfortable humidity levels.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1136 PM CDT Fri May 31 2024

Scattered light showers will affect the terminals at times
overnight, but with little impact. Generally VFR conditions will
prevail, but with pockets and periods of MVFR ceilings that are
difficult to pin down in time. It appears at the northern
terminals MVFR ceilings will be most likely in the next six
hours, then a bit later at the southern terminals into Saturday
morning. Will indicate this trend in the 06Z TAFs, but
amendments are possible overnight.

&&

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

&&

$$

DISCUSSION...REV
AVIATION...Lee