691
FXUS63 KDMX 111120
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
620 AM CDT Sat May 11 2024

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

.KEY MESSAGES...

* Pleasant day today - mid-upper 70s highs with NW winds and
  low humidity.

* Showers/storms return Sunday PM through at least Monday night -
  severe chances very low.

* Additional shower/storm chances mid-late week - details hard
  to come by as guidance diverges

&&

.DISCUSSION...
Issued at 312 AM CDT Sat May 11 2024

After an ideal evening and overnight for aurora viewing across most
of Iowa, today too will be ideal from a Spring weather perspective.
Northern stream shortwave trough will continue to glide through the
Great Lakes and Ohio Valley regions, leaving in its wake general NW
flow and broad subsidence to weak lift. With a substantially dry
airmass in place, only a few higher based clouds may be seen as the
boundary layer attempts to mix to near 700mb. Aside from some weaker
gusts to around 20mph, it will be incredibly difficult to complain
about a day filled with sunshine, highs in the 70s, and low
humidity. Enjoy it if you can!

Sunday will start out quiet enough, but winds will have switched
southerly as the western trough begins to slide off the Rockies and
exert its influence. Deterministic and ensemble guidance remain in
broad agreement on increasing moisture return and chances for
precipitation returning by Sunday evening. The GFS/GEFS members have
slid towards the Euro suite, meaning the primary change/consequence
being lesser opportunity for accumulating precipitation over
northern/northwest areas of Iowa. Potential for stronger/severe
storms remains low with woeful wind fields expected. There could be
a low-end heavy rainfall risk over southern areas with a combination
of initial evening MUCAPE values in excess of 1000 J/kg, mean flow
under 20kts, and overnight Corfidi vectors suggesting extremely slow
to nil propagation. Working against though will be a weak LLJ and by
virtue moisture transport. Overall precipitation activity will
linger over central to southern areas much of Monday, and possibly
into Tuesday over SE areas, before the parent upper low slides
eastward across Missouri and into Illinois and the lower Ohio
Valley.

Guidance continues to consistently signal additional activity by
Wednesday into Thursday as shortwave energy slides southeastward out
of British Columbia, but this is also where deterministic guidance
begins to diverge more substantially in their handling of this
energy and beyond. Extremely hard to hang your hat on any details,
aside from shower/storm chances in general Wednesday into Thursday,
let alone to end the week into next weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 617 AM CDT Sat May 11 2024

VFR is the name of the game today. Winds will predominantly be
out of the NW around 10kts with G20kts possible at times. Winds
then quickly turn southerly after 00z, but under 10kts. Little
cloud cover today, deep mixing may yield FEW090 in addition to
eroding FEW250.


&&

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

&&

$$

DISCUSSION...Curtis
AVIATION...Curtis