Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 152018

Area Forecast Discussion
National Weather Service Des Moines IA
318 PM CDT Sun Oct 15 2017

.SHORT TERM.../Tonight through Monday/
Issued at 318 PM CDT Sun Oct 15 2017

Relatively quiet forecast for this period as ridge axis passes
through the state. Any remaining clouds will dissipate early in
the forecast period as the drier low level air overspreads the
state. Winds will also weaken as mixing begins to subside with
loss of daytime heating. Main concern for tonight with be extent
of frost across the area as temperatures drop into the 30s in most
locations. Lowest readings are expected in the Nishna valleys of
the far west and southwest portions of the forecast area as well
as favored locations in the far north. Temperatures certainly
sufficient for some frost development toward daybreak on Monday.
However coverage may be limited in some areas as a light west
should sustain itself overnight given that the center of the high
goes south of the state. Should be sufficient frost in protected
areas and river valleys for frost development and have gone with
an advisory in the far west and north for this potential.

Otherwise, warm advection will begin on Monday under sunny skies
with temperatures rebounding to normal levels. Winds will become
more southwesterly and increase some by midday as pressure
gradient starts to tighten.

.LONG TERM.../Monday night through Sunday/
Issued at 318 PM CDT Sun Oct 15 2017

The long term forecast is unusually quiet for a change. From
Monday night through Wednesday benign west northwest flow over
Iowa will become zonal, while at the surface winds will be out of
the southwest. A weak surface trough will move across the area on
Wednesday night but with no available moisture and very little
temperature advection, then the trough will wash out and rebound
northward on Thursday. From Thursday into Friday a mid-level ridge
will move overhead, coincident with a return of more brisk
southerly flow at the surface. The effect of all this will be a
glorious week of fall weather for the entire service area, with
abundant sunshine and temperatures peaking in the upper 60s to
mid-70s each day.

By late Friday a large trough will have built into the western
U.S., and will gradually progress eastward across the Midwest next
weekend. There are some timing differences, but the general
consensus is that the associated surface front will cross Iowa on
Saturday or Saturday night, accompanied by at least a broken band
of showers and thunderstorms. Instability is limited and flow
fields are not as strong as the system yesterday, so the
probability of severe weather is low. This also provides the only
chance whatsoever for precipitation in the next seven days and
beyond, as behind the front high pressure will build in again for
the early part of next week.


.AVIATION.../For the 18Z TAFS through 18Z Monday afternoon/
Issued at 1231 PM CDT Sun Oct 15 2017

MVFR ceilings in eastern Iowa will dissipate this afternoon with
unrestricted ceilings tonight into Monday. Visibilities will also
be unrestricted with widespread VFR conditions area-wide late this
afternoon through the end of the period. Winds will weaken by this
evening and be light from the west to southwest into Monday





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