448
FXUS63 KDMX 140514
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1214 AM CDT Sun Jul 14 2024

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

.KEY MESSAGES...

- Heat Advisory in place this Evening and Sunday with some
  expansion of advisory possible Sunday.
- Highs as warm as lower/mid 90s through Monday
- Some risk of storms north/southeast tonight, Sunday with more
  widespread chances Monday.

&&

.DISCUSSION...
Issued at 236 PM CDT Sat Jul 13 2024

.Short Term /Tonight through Sunday Night/...

Confidence Short Term:  Medium to High

Main concern this period will be heat and some risk of severe
weather in the north. Relatively weak sfc features over the region
at the moment with trough of low pressure in eastern Dakotas south
to eastern Colorado. Warm front stretches from eastern South Dakota
to eastern Iowa with an outflow boundary from overnight MN storms
edging southwest into southern MN this morning. Aloft there is a
wave reflected at H850/H700 over Nebraska into western Iowa. This
feature is expected to track east overnight tonight. Somewhat
complicated mesoscale scenario over the region which is not being
handled well by any of the CAMS today. While H700 temperatures are
not capped over eastern Iowa this morning, synoptic models are
slowly building heat aloft into 12z Sunday with H700 temperatures
rising to 10 to 13C over the region by 00z and roughly the same
through 12z. Overall the risk areas for storms will remain the same
this forecast cycle with northern areas nearer the outflow/warm
front and the southeast which may benefit from slightly stronger
forcing overnight into early morning Sunday. This afternoon SBCAPE
forecast for the north is likely to be 4000 to 5000 j/kg across the
sfc frontal corridor, though the H700 cap aloft will increase to
about 11C. At this time, the amount of surface convergence is
expected to remain low over the north. If the lack of mass convergence
along the boundary continues as forecast, this should lessen the
chances of initiation over northern Iowa. Tonight the steering
currents will help push any developed convection mainly east
with time as that and the cap aloft continues to build into the
region overnight. Highs today have been tracking slightly higher
than forecast in the south and lows tonight will likely be a
bit warmer over the area as well. There remains some uncertainty
in the southeast overnight tonight with regard to storm development.
Though the CAMS are maintaining little risk of storm development,
the GFS/GEFs and to a lesser degree, the EC/EPS both show some
development in the southeast. Placement and coverage, though,
remain rather small. Highs Sunday will get an early boost from
overnight mins being so warm. By afternoon, highs will once
again be in the lower to mid 90s with afternoon heat indices in
the upper 90s to lower 100s. We have gone ahead and issued
another heat advisory in the same areas as today. There may be
a need to expand the advisory farther north/east Sunday.

.Long Term /Monday through Saturday/...

Confidence: Medium to High

Hot and humid weather will continue Monday with an area more
restricted to the south. By Monday the front will begin to slip
south, driven by convection over MN and Iowa. Models differ on
timing of most coverage, whether 18 to 00z or 00 to 06z but in
either case there should be a more widespread chance of storms with
some stronger to severe storms possible, along with brief heavy
rainfall. The current marginal risk may need to be expanded over the
area for Monday in future updates. Both the GFS/EC deterministic
solutions are showing increased shear in the afternoon/evening
periods Monday. The main difference currently is the H700 cap which
is stronger, longer in the operational GFS.  The GEFS solution
supports the more capped GFS while the EPS solution is more
convective than the GFS suite, while slightly less than the
operational EC. Will maintain the current blended forecast for
Monday with scattered storms in the afternoon and evening periods
over most of the forecast area along the boundary. Highs Monday will
reach the upper 80s north to the mid 90s south; heat indices
reaching the upper 90s to lower 100s south of US30. The good news is
that once the boundary gets pushed south of the area, a Canadian
high is expected to take up residence over Great Lakes and extend
into Iowa for much of the remainder of the week. With H850
temperatures lowering to around 10C from Wednesday to Saturday,
highs should settle into a mid 70s to lower 80s range.  Tuesday will
be the transition day, with perhaps a slightly bigger temperature
spread from north to south.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1215 AM CDT Sun Jul 14 2024

Maintained VFR conditions through the period at all terminals,
though there remains a high degree of uncertainty in what, if
any, storms may affect the state. One cluster over central
Minnesota is dropping southeast at this hour and current trends
would keep it likely east of MCW and ALO. Another area of storms
over western South Dakota may reach western Iowa before
sunrise if it holds together, but any terminal impact would be
after 12z. Even if storms do not directly move over the state,
there could still be outflow related wind shifts that may cause
a variation in wind direction that is not reflected in the
official forecast later in the day Sunday. Staying with the
assumption of no storms moving into the state, it looks like
another round of diurnally driven cumulus that could be around
FL030 starting mid-morning. For now, have capped at SCT, though
Saturday ceilings were in BKN in MVFR and will need to

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM to 8 PM CDT Sunday for IAZ004-015-023-
024-033>035-044>048-057>062-070>075-081>086-092>097.

&&

$$

DISCUSSION...REV
AVIATION...Ansorge