Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 161953

Area Forecast Discussion
National Weather Service Des Moines IA
253 PM CDT Fri Jun 16 2017

.SHORT TERM.../Tonight through Saturday/
Issued at 251 PM CDT Fri Jun 16 2017

Main concern is severe weather potential and its timing both this
evening/tonight and Saturday afternoon.

Have nudged timing of thunderstorm activity slightly later, to
more of a 00Z or after time period. Surface warm front has pushed
northward and as of early this afternoon extended ESE from
northwest into east central and southeast IA. A weak low existed
across northeast NE with a trof/dryline extending southwestward
from it. MUCAPE values of 3000 J/kg or more existed in the warm
sector. SPC has maintained Enhanced Risk of severe weather across
much of the southwestern CWA. Main threats will be large hail
initially, then evolving into a wind threat.

The storms are likely to continue through the late evening and
early morning hours Saturday across the southeastern CWA,
eventually exiting the area by around 2 to 4 am across the
southeastern CWA. Lows will fall into the 60s once again with the
low/front pushed into southern Iowa.

On Saturday, more severe weather is possible but uncertainties
regarding the location of the frontal boundary remain. Present
thinking is that the best severe weather potential will be
confined to the southern CWA. SPC has an Enhanced Risk of severe
weather there, with the best timing beginning in the mid to late
afternoon hours.

.LONG TERM.../Saturday night through Friday/
Issued at 251 PM CDT Fri Jun 16 2017

The long term period will be characterized by unsettled weather
with opportunities for precipitation early in the period, then by
mid week and again later in the week. Temperatures will begin the
period with near to below normal temperatures, followed by a warm-
up by mid week.

The period will begin with walking the showers and thunderstorms
out on Saturday night. Sunday looks to be much cooler than the
temperatures we have experienced over the past several days. High
temperatures will be in the 70s. By mid-week the upper level
pattern will flatten, returning southerly surface flow and
temperatures well into the 80s. Additionally, a few shortwaves
will move through to end the week, however timing them and
resulting storms is difficult at this time.


.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1113 AM CDT Fri Jun 16 2017

Main concern this period will be severe convection. Storms
expected to fire 20-22z northwest/north then develop south
southeast with time. Best dynamics/bulk shear/instability will
favor greatest threat from KFOD south southeast to KDSM from 22z
through 04z with possibly less intense storms near KMCW/KALO and
KOTM. Early in event large hail main threat then damaging wind aft
00-01z. Airport operations managers at KFOD/KDSM most likely to
see impactful storms and have hit these sites harder with
wind/+TSRA. Elsewhere less confident on higher end severe. Hires
models suggest 23-08z most impactful timeframe. Storms may
accelerate southeast with time to 40- 45kt aft 01Z. MVFR cigs
introduced at some TAF sites for Saturday morning.





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