101
FXUS63 KDMX 061139
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
639 AM CDT Mon May 6 2024

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

.KEY MESSAGES...

- Breezy southeast wind this afternoon, approaching advisory
  criteria in northwest Iowa.

- Strong to severe storms sweep across Iowa this evening and
  overnight. Damaging wind and perhaps a few tornadoes are the
  primary hazards. Pockets of locally heavy rain are also
  possible.

- Additional storm chances on Wednesday and into the latter
  half of the week.

&&

.DISCUSSION...
Issued at 245 AM CDT Mon May 6 2024

With high pressure sliding east winds have shifted to southeasterly
with increasing scattered cloud cover. Further west we catch an
early glimpse at the incoming system moving across the central
Rockies. The pressure gradient has tightened ahead of the
system across the central plains and will continue to do so into
Iowa later today. This will resulting in rather breezy
southeast winds gusting over 30-35+ mph at times this afternoon.

Convection approaches far western Iowa around 5-7pm and the QLCS
will sweep across Iowa through the rest of the evening and
overnight before exiting east early Tuesday morning. The
parameter space remains similar to the past few discussions with
MLCAPE around 1000- 1500 J/kg, deep layer shear 40-50 kts, and
sweeping hodographs in the lower 2-3 km with 200+ m2/s2 SRH at
onset. While lapse rates are rather modest and will offset much
of the hail potenitial, damaging winds and a few tornadoes are
possible within the line. The low level jet will help to
maintain storms through the overnight, however with waning
instability the expectation is for storms to begin to weaken
later in the evening, especially east of I-35 late Monday night.
Thanks to the progressive nature of the line of thunderstorms
widespread hydro issues are not anticipated, however 1-1.5" QPF
remains on track and should fall in a narrower time frame with
these efficient rain producing storms. As such, a few areas
with rivers already in or near flood could see quick rises and
will need careful monitoring.

A few showers and thunderstorms linger in eastern Iowa Tuesday
morning as the system shifts east. The upper level low remains
largely stationary through this and a few spotty showers or
thunderstorms are possible in far northern Iowa on Tuesday
afternoon with afternoon heating. By Wednesday this wobbling
upper level low spins off another surface low. This will bring
renewed chances for showers and thunderstorms. While
instability and shear are sufficient, there is not a great
forcing mechanism for convection so more organized severe
storms appear less likely for now.

The whole trough finally lifts east by Friday, however another
wave may move across the area quickly on its heels Friday into
Saturday. With such an active pattern model solutions diverge
this late in the period so details on the timing and
progression are fuzzy at this time.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 639 AM CDT Mon May 6 2024

MVFR stratus across southern Iowa will expand through the day.
At the same time southeast winds will increase with gusts of 25+
kts through the afternoon. This evening strong to severe
thunderstorms will sweep across the area late, impacting sites
after 02z and lasting through at least 06z before starting to
exit east toward the end of the period.

&&

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

&&

$$

DISCUSSION...Hagenhoff
AVIATION...Hagenhoff