857
FXUS63 KDMX 161130
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
630 AM CDT Sun Jun 16 2024

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

.KEY MESSAGES...

- Storms ending this morning except possibly the far southeast.
  Additional storms possible far north late this afternoon and
  especially tonight. A few severe storms could occur.

- Heat indicies of 95 to 100 possible today and again Monday.

- Storm chances return Tuesday night and Wednesday. A few severe
  storms again will be possible.

&&

.DISCUSSION...
Issued at 411 AM CDT Sun Jun 16 2024

A complex of storm is currently lifting slowly lifting northeast
across parts of central and northern Iowa with additional activity
in far southwest Iowa and back into northeast Kansas. Gusty winds
and brief heavy rain continue with the Iowa storms and should be out
of the forecast area by around 7 am. The activity over southwest
Iowa and into Kansas is a bit of a wild card as there is potential
that an MCV will evolve from it and it could trigger convection as
it spirals east/northeast and could bring some convection into
southeast Iowa later this morning. Have added low pops to this area
and will continue to monitor this activity and adjust pops as
necessary.

For today, surface low pressure over north central South Dakota will
lift northeast into northern Minnesota while lee side cyclogenesis
over eastern Colorado occurs leading to another area of low
pressure, with a boundary linking the two. This will drag the
boundary into north central and northwest Iowa today while the
thermal ridge leans into the state ahead of this boundary. The
instability axis will reside in vicinity of the surface boundary
along with pooling dew points in the low 70s on the south side of
the boundary. There are a lot of things to unpack here from storm
chances to heat potential. Let`s tackle the heat first. As discussed
previously, the NBM has been running quite warm with the upcoming
highs for Sunday and Monday and this is being caused by the warm
bias correction that is being ingested into the guidance from
numerous sources and this drives the NBM itself to near the 75th
percentile. While the thermal ridge will be moving over the state
today, deeper moisture will be in place as well, which makes it more
difficult to heat than drier air. Thermal profiles also do not
support the current NBM forecast so will continue to adjust below
that. Finally, highs under the thermal ridge upstream did not reach
these warmer values and expect the same today through Monday. So it
will be warm but expect the NBM temperatures to underperform.

With the boundary and the instability axis in the area this
afternoon, a few storms could develop in northern Iowa but it does
appear the elevated mixed layer (EML) capping should hold most of
the day in that region and it does not appear there will be enough
large scale forcing to help punch through any convective inhibition.
Have held low pops in northern Iowa but again better chances it
stays dry. The main complex of storms is expected to the north in
South Dakota and Minnesota overnight. There most likely will be
outflow dropping south from these storms into northern Iowa later
tonight and into Monday morning with convective bubbling occurring
as the outflow proceeds south. It is possible the outflow is near
severe early and there is enough CAPE and updraft acceleration
potential for a few storms with large hail.

Monday`s weather will be dependent on the aforementioned outflow
boundary and how far south it can get and maintain. Guidance
suggests it should erode or be pushed back to Minnesota. This is
likely as a large subtropical high protrudes further north into the
New England region while an upper level low moves east to near
Idaho. This will steepen the southwest flow aloft which would
promote driving any boundary quickly north by the afternoon as the
capping EML spreads back over the area. The sub-tropical high is
looking stronger and further north than previous projections. The
surface boundary should move into Iowa Tuesday night and into
Wednesday and will bring a return for thunderstorms chances, a few
of which may be severe. The boundary though likely will stall over
Iowa and should be pushed back to the north as the sub-tropical high
ridging into mid-Mississippi River Valley increases. This will bring
the above normal temperatures back to the forecast Thursday and
Friday.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 628 AM CDT Sun Jun 16 2024

A few storms early vicinity KMCW/KALO and near KOTM late
morning. MVFR cigs may occur near the storms far north and
possibly local IFR. Otherwise, mostly VFR today with breezy to
gusty south to southwest winds. There is a low chance for
storms over northern Iowa this afternoon followed by a greater
chance overnight.

&&

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

&&

$$

DISCUSSION...Donavon
AVIATION...Donavon