FXUS63 KDMX 211048

Area Forecast Discussion
National Weather Service Des Moines IA
548 AM CDT Mon Oct 21 2019

...Updated for 12z Aviation...

.DISCUSSION.../Today through Sunday/
Issued at 353 AM CDT Mon Oct 21 2019

Overnight through the early morning hours a line of convection has
pushed across Iowa, with a widespread rain totals of 0.5 to 1.0
inches. A few location have received over 1.5 inches in some of the
heavier cores. This line will push off to the east this morning with
rapid clearing on the back edge as the dry slot and subsidence
region of the low move into the state. More rain is on the way
however, with the wrap around portion of the low currently over
South Dakota and Nebraska set to move eat into the state by midday.
This should linger rain across northern to central Iowa through the
overnight hours before finally lifting out of the area.

The other, more pressing, concern as the low shifts east is the
gusty winds associated with the tight pressure gradient on the back
side of the system. Winds will begin increasing this afternoon and
remain gusty through the overnight hours and much of the day on
Tuesday. Models are in good agreement with pressure changes of 3-
5mb/3hrs across northern into central Iowa during this time.
While the mixing layer is fairly shallow, it is sufficiently deep
to mix down gusts in the 45 to 50+ kt range. As such, have issued
a Wind Advisory for Monday evening through Tuesday across northern
and central counties but this may need to be extended further
south to include much of the cwa in future updates. In addition,
with soundings showing occasional gusts of 50+ kts there is the
chance that portions of this will need to be upgraded to a High
Wind Warning, particularly over northern counties, but have held
off for now.

Wednesday will see a bit of return flow with warm air advection into
southern portions of the area. This will be short lived as a longwave
trough over the western US digs across the northern plains into Iowa
Wednesday into Thursday. A leading embedded shortwave will bring
precipitation across northern portions of the cwa Wednesday
morning, and with cold air advection dropping temperatures this
area could see non-impactful snow or rain/snow mix before
transitioning to rain by late morning. The larger longwave trough
moves across Iowa Thursday with cold air advection across the
state dropping highs into the 40s. Cooler than normal temperatures
continue through the end of the week, with a chance for warming
into the weekend with the trough pushing east and southerly return
flow moving into the area. Breezy conditions possible again on
Saturday with tightening pressure gradient over the state, however
with model differences and this extended time frame confidence in
details is fairly low.


.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 548 AM CDT Mon Oct 21 2019

A line of convection is moving across central Iowa this morning,
with cigs across the state at IFR to LIFR categories. Southern
iowa may see brief clearing by midday, however wrap around rain
and low stratus deck will keep central to northern Iowa in MVFR to
IFR categories through most of the day. By this afternoon concerns
then shift to winds, with gusts of 30 to 40+ kts by tonight. Gusty
winds expected to continue throughout much much of the day on


Wind Advisory from 5 PM this afternoon to 4 PM CDT Tuesday for




NWS DMX Office Area Forecast Discussion