234
FXUS63 KDMX 070401
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1101 PM CDT Wed May 6 2026

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

.KEY MESSAGES...

- Patchy, low-lying frost for a few hours 3 to 7 am Thursday
  (tonight).

- Several chances for showers and thunderstorms from Thursday
  night through early next week. Highest chance up to 60 to 70%
  Saturday night over southern Iowa. No apparent signal for
  significant severe weather or heavy rainfall with any storm
  chances.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 128 PM CDT Wed May 6 2026

Winds from the northwest have continued to reinforce the cool
and dry conditions across the region today as surface high
pressure moves southeastward over the Rockies onto the Colorado
Plains. While there was an area of clouds over northern Iowa to
start this morning, the steep lapse rates have allowed for
cumulus clouds to develop and become widespread as the profile
saturates around 5- 7kft. Below this saturated layer, the
boundary layer is quite dry with an inverted V sounding. This
should result in efficient momentum transport and have increased
winds above initial National Blend of Models along with
lowering dewpoints and resultant RHs. These brisk breezes will
be pared with RHs around or less than 30% over western into
southern Iowa; however, increasing green fuels will mitigate any
fast fire spread concerns.

The diurnal cumulus clouds this afternoon will dissipate after
sunset. However, additional low and mid clouds will spread in after
midnight as weak to perhaps modest theta-e advection and QG
convergence begins to impinge on the state ahead of the next
shortwave trough within the broad cyclonic flow. With the low
dewpoints, temperatures may fall off quickly as the cumulus
dissipate, but stabilize as the clouds move back in. The frost
potential, therefore, is tricky with the incoming clouds. Current
thinking is that frost that does form will not be widespread or
prolonged and more transient. The favored locations for this short-
lived, transient frost is in and around the Nishnabotna River Valley
and low areas in the Iowa and Cedar River basins.

The aforementioned forcing on Thursday will pass through the state,
but lacks much in the way of moisture in the atmosphere. Convective
allowing models (CAMs) are painting model reflectivity returns, but
not much in the way of QPF outside of the NAMNest, NAM, and GFS.
Given the amount of dry air, especially sub-cloud, along with the
generally weak forcing, have kept any shower mention out and may
look at adding sprinkles in a future update. Given the dry boundary
layer, this does raise the concern for virga gusty winds. Downdraft
CAPE values never exceed 500 J/kg and CAMs are not showing any gusts
higher than 30 knots in their model fields. In addition, the deep
boundary layer mixing will once again lower dewpoints with resultant
RHs dropping below 25% west and north of an Atlantic to Ames to
Waterloo line. One to two months ago, this low of RH would have led
to critical fire weather conditions; however, as discussed above
increasing greenness along with the relatively strongest winds of 10
to 20 mph displaced from the lowest RHs, preclude any concern for
rapid, uncontrolled fire spread.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 128 PM CDT Wed May 6 2026

Additional shortwaves will move through the region late this week
into perhaps early next week. The rough timeframes and possible
areas for scattered showers and storms are as follows: 1) late
Thursday night into Friday morning, primarily southern Iowa,
2) late Saturday into Sunday morning with chances highest over
southern Iowa, and 3) late Monday into Tuesday over the state.
In all instances, there is no apparent signal for significant
severe weather or heavy rainfall concerns from a pattern
recognition and diagnostic standpoint. Examining the ML/AI
guidance generally supports this idea with EC forced data
pointing to up to 15% chance on Monday/Monday night while the
GFS/GEFS is lower or none. Temperatures in this period will
largely be around if not above normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1057 PM CDT Wed May 6 2026

VFR conditions ongoing and expected to continue through the TAF
period. Clouds continues to linger over portions of northwest
Iowa with additional clouds streaming into southern into
portions of central Iowa overnight into Thursday morning. Dry
air continues to look to limit sprinkle/light rain chances near
KDSM/KOTM Thursday as seen in many CAMs, so kept forecast dry.
After some clearing Thursday evening, additional clouds move in
overnight into Friday. Winds may be a bit breezy at times in
especially southern Iowa Thursday after remaining light and
variable through the overnight hours.

&&

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

&&

$$

SHORT TERM...Ansorge
LONG TERM...Ansorge
AVIATION...05