698
FXUS63 KDMX 071921
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
221 PM CDT Sat Jun 7 2025

.KEY MESSAGES...

- Scattered showers and storms this afternoon with chances waning
  quickly toward and after sunset.

- Shower and isolated storm chances along a cold front Sunday.
  Low chance of severe weather in southeast Iowa late morning
  and early afternoon.

- Gusty winds of 20 to 30 mph after the front passes Sunday and
  again during the day Monday.

- Seasonal to a bit below normal temperatures through Monday,
  then warmer and turning more humid.

&&

.DISCUSSION...
Issued at 221 PM CDT Sat Jun 7 2025

GOES-East upper level water vapor imagery shows the compact
shortwave trough tracking over the Iowa-Missouri area this
afternoon. This shortwave along with its associated QG
convergence and low level theta-e advection have been the
impetus for the showers and storms today. A broad area of
rainfall has been over southern Iowa closer to the shortwave,
but there have been isolated pockets of heavy rainfall elsewhere
in central Iowa including northern Dallas into Boone and
northern Wright and southern Hancock into Cerro Gordo counties.
RAP mandatory level analysis shows weak flow, generally around
or less than 5 knots in the lower half of the atmosphere. Midday
KOAX RAOB confirms this weak flow with no higher than 10 knots
from 700mb to the surface. This has resulted in prolonged
rainfall with moderate to at times high rates. The highest
rainfall totals have been over parts of southern and eastern
Taylor County where personal weather stations have reported over
2.5 inches of rainfall, which is supported by MRMS and radar
estimated amounts. While several basins were nearing over an
inch of flash flood guidance, FLASH streamflow and annual
recurrence intervals (ARIs) were more muted. While smaller
streams likely have experienced rises in the area of highest
rainfall, Taylor County public safety has not reported any
issues as of early afternoon.

The showers over southern Iowa are scooting off to the east with
other showers over parts of northern and central Iowa slowly
moving that direction as well. We have also seen additional
isolated storm development, which will be possible the
remainder of the afternoon, along the cloud shield and its
differential heating boundary. While this has allowed for some
instability to build, severe weather is not expected given weak
midlevel lapse rates and the weak shear as stated above.

Attention overnight will turn to a cold front that is associated
with a more potent longer wave trough, which will drop out of Canada
into the Great Lakes region early this upcoming week. Scattered
showers and isolated storms should be able to form along this front
given the ribbon of theta-e advection. The best phasing of low and
mid-level forcing continues to look to be over northeastern Iowa and
points northeast. Thus, the higher chances for this scattered
activity will be over northeastern into eastern Iowa. Farther west,
activity may be more broken/hit and miss, but there may be a more
prolonged window as the forcing is spread more east to west. SPC`s
day 2 outlook has maintained a low risk of severe weather over our
far southeastern forecast area. This could materialize if the front
doesn`t clear out all the instability first, in which case a short
window of severe weather is possible late morning and early
afternoon. This is when soundings show over 1000 J/kg of
instability, but a largely unidirectional wind profile with weak
effective shear. So, hail would be the primary concern with gusty
winds a secondary concern if storms can form over our area. Behind
the front, winds from the northwest will increase and average 10 to
20 mph with gusts of 20 to 30 mph mid to late morning into the
afternoon. The highest wind speeds and gusts will be over north
central into northwest Iowa. Also behind the front will be the next
round of high level smoke, which may add vibrancy to the sunset
where the clouds do clear by Sunday evening.

Monday will feature another round of breezy winds from the northwest
as the longer wave trough moves east over the Great Lakes region.
Another lobe of vorticity will rotate around in the cyclonic flow
and bring clouds back over northern Iowa along with shower chances
from north central into parts of east central Iowa. The more
amplified flow over our region will flatten as a mid-level
ridge enters the central part of the US into midweek.
Temperatures and increasing humidity will be present by then
through the end of the week as dewpoints climb into the 60s. A
cold front will descend from Canada, but stall north of Iowa
and with the fast moving shortwave flow, we will see storm
chances at times in the latter half of the week. Initial
National Blend of Models guidance is likely overdone on temporal
extent of these chances, but it seems reasonable that the
higher chances will be over northern Iowa and points north
closer to the stalled boundary.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1214 PM CDT Sat Jun 7 2025

Scattered showers and storms were over central Iowa early this
afternoon and these are causing visibilities to drop into MVFR
or briefly IFR while ceilings may briefly drop out of VFR.
With the exception of OTM where a broad area of rainfall will
move across this afternoon, timing much of the rest of this
activity is difficult. This has resulted in some long PROB30
groups. Overall, this activity will be moving east and
diminishing late this afternoon and early this evening with VFR
conditions returning. Then, attention will be on a cold front
that will bring lowered, but still mainly VFR ceilings and a
shift in the wind from the south to from the northwest by late
in the period. Have maintained PROB30 group at ALO for possible
showers along this front, but have removed thunder mention due
to low confidence. Additional PROB30 or prevailing groups may
be needed in future updates at other terminals.

&&

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

&&

$$

DISCUSSION...Ansorge
AVIATION...Ansorge