Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 202323

National Weather Service Des Moines IA
623 PM CDT Thu Oct 20 2016

.SHORT TERM.../This evening through Friday/
Issued at 342 PM CDT Thu Oct 20 2016

The main forecast concern tonight was focused on temperatures and
frost potential over the CWA. The south-central to southeast still
has yet to experience freezing temperatures and thus lead toward
a frost advisory in this location. Temperatures look to bottom out
in the 33-35F range. Cooler further west and north as radiational
cooling sets up across central Iowa with the surface high
centering itself directly overhead. However, with these location
already experiencing freezing temperatures, held off on any
headlines attm but have mention of frost for continuity across the

.LONG TERM.../Friday night through Thursday/
Issued at 342 PM CDT Thu Oct 20 2016

Friday through Monday...With the 500mb trough moving east of the
state during the day Friday, a large upper level ridge begins to
build into the region and looks to persist through early next week.
Dry forecast through the weekend into Monday, with the only concern
focused on temperatures throughout the period and on winds Sunday. A
weak mid-level shortwave cuts southeast out of southern Canada
Sunday morning and brings some gusty winds during the afternoon
hours as mixing increases. Nudged up the winds/gusts during the
day Sunday.

Tuesday through Thursday...A fairly strong upper level shortwave
and associated surface low pressure will bring increasing chances
of rain by early Tuesday morning. Ahead of the main surface low,
mid-level theta-E advection should help spawn some showers and
thunderstorms, and thus cloud cover throughout the day Tuesday.
This should inhibit the CAPE building into the state. The GFS and
ECMWF are in decent agreement with timing and location of the
strong surface low Tuesday night into Wednesday. The strongest
forcing and deepest moisture available look to be late Tuesday
night into Wednesday morning. As mentioned above, limited
instability with this system but good deep layer shear along with
decent veering through the profile. Plus, strong deep QG forcing
Tuesday night combined with a decent PV anomaly pushing across the
state Wednesday morning should be enough to keep mention of
thunder going. Timing is the key if any instability can build into
the state during the day Tuesday whether or not the first weaker
system can dissipate to allow for destabilization during the day.
The main threat looks to be locally heavy rain. The is plenty of
theta-E advection ahead of the trough Tuesday night with PWATs
nearing 1.0 inch and for this time of year close to the 90% of the
mean. Low confidence with any severe weather attm but locally
heavy rain seems to better threat.


.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 622 PM CDT Thu Oct 20 2016

Band of eroding stratus over western Iowa is expected to remain
west of sites overnight. Light winds and VFR conditions will
prevail overnight. Light southwest winds are expected on Friday.
Mid level clouds will increase during the afternoon.


Frost Advisory from 3 AM to 8 AM CDT Friday for IAZ073>075-



SHORT TERM...Podrazik
LONG TERM...Podrazik
AVIATION...Donavon is the U.S. government's official web portal to all federal, state and local government web resources and services.