FXUS63 KDMX 222008

Area Forecast Discussion
National Weather Service Des Moines IA
308 PM CDT Fri Jun 22 2018

.DISCUSSION.../Tonight through Friday/
Issued at 115 PM CDT Fri Jun 22 2018

It`s been a relatively cool start to astronomical summer as the
state resides on the backside of a slowly departing upper level
low. Cool northeast winds and expansive cloud cover have held
temperatures in the upper 60s to mid 70s. Winds become light and
variable tonight as surface high pressure crosses the state, but
lingering cloud cover and low level moisture will hold low
temperatures in the upper 50s.

Synoptic pattern over the central conus becomes more zonal this
weekend as the upper low opens up and kicks east, while a series
of shortwave troughs dig into the northern Rockies. Low level
cyclogenesis to our west returns warmer southerly flow to the
region, bringing a more summer-like feel to the air as highs
bounce back into the 80s. Scattered showers and storms are
possible Saturday night into Sunday as the first shortwave moves
across the northern Plains, but the better chances for rain hold
off to Sunday night into Monday as a deeper wave ejects into the
central Plains. Strong to severe storms over KS/NE will likely
congeal into some sort of QLCS/MCS complex by Sunday evening,
then track east along warm front draped somewhere near the IA/MO
border. 0-3 km shear values in this vicinity increase to around
25-35 kts in concert with a strengthening LLJ, which may be enough
to maintain a balanced cold pool and a threat for severe wind
gusts. Further north widespread showers and storms will likely
develop Sunday night in a zone of isentropic ascent north of the
warm front.

Upper level low slowly nudges east on Monday as the surface warm
front slides north through the state. Strongly diffluent flow
aloft on top of a deeply moist airmass will promote high chances
for showers and storms through much of the day. Locally heavy
rainfall will be a concern, especially in vulnerable areas of
northern and central Iowa that have little capacity for
additional rainfall at the moment. Severe weather is a
possibility as well especially as deep layer shear increases to
near 40 kts by late day, however confidence remains low as
widespread precip may limit surface based instability.

Euro/GFS look to be settling on a zonal pattern through the middle
of next week. Surface high pressure over the southeastern states
will maintain a southerly fetch of warm and humid Gulf air into
the region. Subtle waves crossing the region keep periodic PoPs in
the forecast, including the potential for more locally heavy rain
and strong to severe storms. The predictability of such events is
low at this time as models struggle with the timing of these
subtle waves in the extended range, and storm chances will be tied
to boundary locations that are hard to pinpoint this far out.


.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1244 PM CDT Fri Jun 22 2018

MVFR ceilings at KOTM and all other locations with VFR
conditions. Conditions at KOTM should improve to VFR after 21z
this afternoon. Winds will gradual transition over the TAF period
from the north to out of the south, remaining below 12 kts across
all sites.






NWS DMX Office Area Forecast Discussion