Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 211741

Area Forecast Discussion
National Weather Service Des Moines IA
1241 PM CDT Fri Sep 21 2018

.DISCUSSION.../Today through Thursday/
Issued at 351 AM CDT Fri Sep 21 2018

A few lingering showers in the far southeast associated with the
push of the pre-frontal trough earlier tonight, with the true cold
front moving through central IA currently. Westerly to northwesterly
winds beginning to pick up behind the front with sustained winds
around 15 to 20 mph and gusts to around 30 mph or higher across
central/northern IA. The sfc low has lifted to the Lake Superior
area and will continue to move ENE into the Hudson Bay region later
today. The upper level trough is moving through the Dakotas and will
continue to move east into Ontario today. Some low stratus is
situated on the backside of this system and is pushing into IA
currently. This area of low clouds is expected to remain across the
area for much of the morning hours, before beginning to lift and
break up into the afternoon hours as drier air moves in with an area
of high pressure building into the state. Strong CAA in place today
with a tight sfc pres gradient and strong winds aloft translating to
the surface. This will allow for the gusty west to northwesterly
winds to continue through much of the day. Expect winds to stay
below advisory criteria but a gust to around 35 to 40 mph at times
will be possible. High pressure to continue to build into Iowa this
evening and be centered across Iowa tonight with clearing skies.
This will allow temperatures to drop off quite a bit overnight, and
with the chilly air in place, expect temps to drop into the upper
30s to mid 40s tonight.

Dry and cool conditions continue into the weekend with the area of
high pressure dominating the region beneath broad upper level
ridging and the jet stream remaining further north across the far
northern US/southern Canada. Winds to shift around to the south into
Saturday/Sunday with return flow setting up Sunday into Monday ahead
of the next upper level wave set to move through the northern
Rockies Sunday into Sunday night. This will allow for warming
temperatures back into the 70s for highs Sunday into Monday. This
system will lift through the northern Plains with the sfc low
lifting into Ontario by late Monday with an associated cold front to
drop through IA late Monday into Monday night. This will bring the
next chance for some showers and thunderstorms to the state. A
stronger wave will dig into the Dakotas/Minnesota toward the
middle/late part of the week which will bring additional chances for
precipitation to Iowa. This system will bring a strong cold front
through the state toward the end of the forecast period and just
beyond which will likely send temperatures back below average to end
the week.


.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
Issued at 1241 PM CDT Fri Sep 21 2018

MVFR ceilings are gradually rising today and will primarily affect
only MCW in the next few hours, with the clouds mostly breaking
up before sunset. Strong northwest winds this afternoon will also
diminish greatly after sunset, with mostly clear skies and light
winds by 02Z or so and through most of the night. On Saturday
morning winds will go light and variable then turn to southeast by
the end of the TAF period. The degree to which low clouds will
redevelop on Saturday is uncertain. MVFR ceilings may again be
possible in the morning, but given low confidence have advertised
just SCT030 for now and will reassess overnight.





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