884
FXUS63 KDMX 051147
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
647 AM CDT Wed Jun 5 2024

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

.KEY MESSAGES...

- Few showers or storms possible this afternoon into evening but
  may end up being more vigorous virga with low level dry air.

- Breezy to gusty conditions also expected today, especially
  north, with some strong gust potential near showers/storms
  (virga). Wind Advisory in place mid afternoon into early
  evening for northern Iowa.

- Breezy to windy again Thursday.

&&

.DISCUSSION...
Issued at 352 AM CDT Wed Jun 5 2024

The front that helped kick off our storms yesterday has since moved
through the area with the rain exiting our far southeast around 330
AM. Initially this morning we`ll be in for a quiet morning, though
mixing will start to increase by 15-16Z which in turn will help
increase our winds. Another shortwave and associated cold front will
move into northern Iowa by roughly mid afternoon with the front
pushing through the state into this evening. Model reflectivity in
both CAMs and the deterministic models are littered with
precipitation this afternoon into evening and although a few showers
or storms could be possible north or northeast with lower chances
central and south as the boundary pushes through the area, forecast
soundings paint a different picture. Moisture is going to be a
limiting factor, as mentioned in the previous discussion, with LCLs
looking to be near to over 6000ft and any moisture limited to the
mid levels with significant dry air (inverted-V soundings) in the
lower levels. Mixed layer winds at the bottom of the mixed layer are
around 35 knots up north with 20-25 knots towards central Iowa
providing a floor for potential wind gusts alone today. At the top
of the mixed layer, some soundings at locations like KMCW or KEST
indicate some gusts near 50 or even 60 knots. Although it is
generally unlikely we`ll mix all the way to 700 mb or more even with
our steep lapse rates, the potential is definitely there for gusts
over 39 knots and as such have issued a Wind Advisory for the
northern two tiers of counties to cover this higher wind gust
potential. The caveat to this is some of the higher wind gusts are
likely to be associated with the shower activity which given
the dry air may be more like vigorous virga or rain that
evaporates before it reaches the surface. Even if the rain
doesn`t reach the ground, it could help get some of the stronger
wind gusts aloft down to the surface. Can`t rule out some
severe gusts up north, and some strong gusts outside of the
advisory slightly further south of the northern two tiers of
counties, but most likely area in soundings and HREF
probabilities for the higher gusts are covered in the wind
headline.

The departing upper low will keep hold of our flow for the next
several days as it moves into the eastern CONUS with various waves
at times moving through the otherwise northwest flow. After today,
our next chance for precipitation may not be until Friday night into
early Saturday but uncertainty remains in eastern extent of moisture
return with a high pressure in place earlier Friday. One thing we
will have to watch for is another potential day of wind headlines
Thursday as the upper low moves out increasing the pressure gradient
and in turn winds/gusts. LREF probabilities for wind gusts over
advisory criteria (39 knots/45 mph) are 40-60% in northeast
Iowa with HREF mean gusts around 30-40 mph through much of the
area on Thursday afternoon, the highest gusts in the north.
Temperatures remain pleasant for early June in the 70s to low
80s with notably less humidity into the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 639 AM CDT Wed Jun 5 2024

Widespread VFR conditions ongoing early this morning with VFR
conditions expected to continue through the period despite
increasing scattered to broken cloud cover this afternoon into
early evening with some chances for showers or a few storms.
Northern sites most likely to see any activity today, but may
end up being more virga and not precipitation reaching the
ground and as such, have continued with only VCSH mentions as
confidence in direct impact to TAF sites remains low.
Refinements may still be needed in timing. Winds also pick up
today by about 15-16Z becoming quite gusty at times through the
afternoon. Higher gusts than included are possible around
showers.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 2 PM this afternoon to 7 PM CDT this
evening for IAZ004>007-015>017.

&&

$$

DISCUSSION...KCM
AVIATION...KCM