009
FXUS63 KDMX 082335
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Sat Jun 8 2024

 ...Updated for the 00z Aviation Discussion...

.KEY MESSAGES...

- Sprinkles, a fleeting shower west or south this afternoon or early
  this evening

- Ample sunshine, comfortable temperatures and humidity Sunday,
  Monday

- Warmer weather Tuesday through Friday, storm chances return

&&

.DISCUSSION...
Issued at 149 PM CDT Sat Jun 8 2024

GOES-East upper level water vapor imagery shows a broad trough with
embedded closed lows and shortwave troughs sprawled over the
southern provinces of Canada into the Northeastern US with this
resulting in northwest flow over Iowa. This places Iowa in the
squeeze between the northern jet stream flow around the broad trough
close by to the north with the southern jet stream of shortwaves far
enough away to keep our forecast more tranquil with any severe
threat remaining south of the state through early next week. At the
moment, we reside beneath nebulous shortwave energy as well as the
right entrance region of a departing 115 knot jet streak. These are
the impetus for the clouds entering the western part of Iowa this
afternoon. Radar has shown light returns over parts of Siouxland and
there have a been a few mPING reports in Plymouth County. However,
the farther east towards Cherokee/CKP and Storm Lake/SLB, there have
not been any reports from automated sites or ground observers
whether mPINGs or parents in this same area. The lack of surface
reports is due to plenty of dry air below 700mb/sub cloud layer that
is shown in forecast soundings this afternoon and with surface
dewpoint depressions of 10 to 15F, have trimmed back PoPs a bit more
this afternoon into this evening.

As the jet streak farther departs and the shortwave energy sinks
away as the broad trough breaks apart with one piece deepening over
the Eastern US, this will result in continued northwest to westerly
flow with mostly dry conditions and comfortable temperatures and
humidity by early June standards through Monday. At the same time,
heights will be rising over the western US and as the Eastern US
trough moves away, these higher heights will arrive replacing
comfortable conditions with temperatures above normal Tuesday
through the end of the week. Highs during this period will be well
into the 80s to around 90 degrees. Latest NBM puts the probability
of exceeding 90 degrees on Thursday at 60% or higher roughly south
of Highway 30.

While temperatures will be on the rise, chances for storms will also
return to the forecast. A shortwave trough aloft and a surface low
will ride along the US/Canadian border while a cold front draped to
its south approaches Iowa on Tuesday. MUCAPE of 500-1000 J/kg will
build ahead of this front by mid-afternoon with a marginal amount of
shear for storm organization. While this would result in
thunderstorm potential, any severe risk appears low at this time
with this supported by the SPC day 4 outlook and Colorado State
University`s (CSU) machine learning random forest outlook. While the
cold front will push into Missouri, a warm front and attendant warm
air advection return on Wednesday along with additional storm
chances, especially over northern Iowa into Minnesota and the
Dakotas. CSU outlook does have a broadbrush area of severe
probability, but the jet streak and better forcing will reside over
the Dakotas. More chances may return on Thursday as the front pushes
through the state.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 631 PM CDT Sat Jun 8 2024

VFR conditions will prevail through the period. A few spotty
showers in western and southern Iowa this evening are expected
to remain away from terminals and in many cases precipitation
will evaporate before reaching the ground. On Sunday winds shift
slightly, becoming more west northwesterly. Northwestern sites
KALO and perhaps KMCW will see stronger gusts of 20-25 kts by
afternoon which will be better determined in future updates.

&&

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

&&

$$

DISCUSSION...Ansorge
AVIATION...Hagenhoff