FXUS63 KDMX 030459
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1159 PM CDT Fri May 2 2025

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

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms this afternoon
  and evening. Severe threat is low.

- Temperatures cool off tonight with isolated potential for
  frost in the northwest.

- Generally dry and mild conditions through the weekend and into
  early next week. Rain chances return to forecast middle of
  next week.

&&

.DISCUSSION...
Issued at 239 PM CDT Fri May 2 2025

A fairly pronounced 500 mb shortwave continues through the 
area, which brought a steady rainfall over roughly the southern 
half of the forecast area this morning and scattered showers 
with isolated thunderstorms this afternoon. Expecting these 
scattered showers and occasional thunder to persist into the 
early evening hours until a weak trough eventually pivots south 
through the area. With this trough passage occurring in the late
afternoon and early evening, we may see a small amount of 
instability pool along the boundary, increasing the likelihood 
for thunderstorms as it moves through. These instability values 
will be marginal, generally less than 500 J/kg, and will be 
displaced from the better kinematic environment, effectively 
eliminating any severe weather risk. The vertical profile will 
be fairly cool, so can’t rule out the production of some small, 
sub-severe hail within the pulsey convection, but even then 
there will be very little instability in the hail growth zone to
promote hail production. Once the trough drops through the 
area, precipitation chances will diminish overnight.

Low clouds over the northeastern portions of the state will 
drift southeast and linger in the the eastern portions of the 
forecast area overnight, limiting radiational cooling for those 
areas. However, skies will clear out in the west overnight as 
the wave progresses east and a thin area of surface high 
pressure will set up over the northwestern portions of the 
state. This will allow for efficient radiational cooling beneath
clear skies with light winds. Low temperatures drop into the 
mid to upper 30s, with the potential for some even cooler values
in lower lying areas. Dewpoints will be in the mid 30s as well,
which could lead to isolated frost development in the early 
morning hours on Saturday. With temperatures generally 4-5 
degrees above freezing, not expecting this to be widespread or 
to cause significant impacts. 

As we get into the weekend, the 500 mb trough closes off into 
an upper low and parks itself over the ohio river valley, 
setting up a blocking pattern through the weekend. A secondary 
500 mb trough/low will set up over the western CONUS at the same
time, and remain blocked off by the eastern low through Monday.
This will keep weak high pressure overhead with a relatively 
transient flow pattern, leading to little in the way of 
temperature advection but leaning slightly toward a cold air 
advection regime. However, temperatures will be more greatly 
impacted by insolation and the diurnal cycle, with cloud cover 
being the main driver of temperatures. This will keep 
temperatures cooler in the east nearer to the surface low and 
coincident cloud cover, while areas farther west will see 
clearer skies and warmer temperatures. All in all, this results 
in a pleasant weekend with light winds and highs in the 60s and 
70s across the state.

Monday remains status quo before the upper low finally breaks
off to the east on Tuesday. This will pull the upper ridge into
the state and bring slightly warmer temperatures into the state
on Tuesday. With the blocking low now gone, the pattern opens up
and rain chances return to the forecast through the middle and
end of next week. However, with high pressure moving to our
north, these chances mostly stay to our south for the time 
being. Therefore, will continue to evaluate next week’s rain 
chances through the coming days.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1159 PM CDT Fri May 2 2025

Low MVFR status, with pockets to IFR, lingers across central to
eastern Iowa overnight. The cloud cover is stubborn to lift with
MVFR impacts likely through about 18z on Saturday at KALO/KOTM 
before improvement to VFR conditions at all sites the rest of 
the period. 

&&

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

&&

$$

DISCUSSION...Dodson
AVIATION...Hagenhoff/Jimenez