Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 150516
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1216 AM CDT Sun Oct 15 2017

.SHORT TERM.../Tonight through Sunday/
Issued at 354 PM CDT Sat Oct 14 2017

Convection has remained widespread through the day with strong
warm advection and moisture advection into the state. Surface
front has moved into the state but much of the area has limited
surface heating thanks to the widespread precipitation and low
clouds. This throws the amount of severe convection into question
as the surface front moves across the forecast area this evening.
There is plenty of shear available given the strong wind fields
with this dynamic system. However, surface instability has
remained along and just south of the border of the past few hours.
This may edge into the far south over the next couple of hours
with main tornado threat, albeit isolated over the far south to
southeast areas of the forecast area. Meanwhile, any convection
farther north will likely become more elevated with main threat
becoming hail. This threat will diminish quickly by mid to late
evening as the boundary pushes convection out of the forecast
area.

There will be lingering showers in far northern Iowa on backside
of deformation zone, however focus will then shift to increasing
northwest winds. Anticipate strong subsidence overnight with
strong cold advection and decent pressure rises. Anticipate strong
and gusty northwest winds, especially as stratus remains in most
locations until near morning allowing mixing to remain a bit
stronger. Will see gusts approaching 40 mph with sustain between
20 to 30 mph which is close to advisory, but remaining under at
this point. Sunday will be much cooler with thermal trof overhead
but modified somewhat by generally sunny conditions. Winds will be
brisk from the northwest through much of the day but should
subside by late afternoon as surface ridging approaches.

.LONG TERM.../Sunday night through Saturday/
Issued at 354 PM CDT Sat Oct 14 2017

Clear skies, light winds and a relatively dry airmass will lead to
quick temperatures fall on Sunday night with readings into the 30s
most locations. Frost is expected across a good portion of the
northern half of the forecast area and wouldn`t be surprised to
see some headlines. Otherwise, much of the rest of the extended
will be uneventful with main jet stream axis lifting toward the
Canadian border. With little moisture and/or lift across the
state, little if any precipitation is seen through the work week
with temperatures remaining above normal. There may be some threat
of precipitation by early next weekend but moisture will remain
somewhat limited.

&&

.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1214 AM CDT Sun Oct 15 2017

TAF forecast becomes less complex as precip removed from forecast.
Wind shift and gusty winds reason for FM groups early on.
Confidence increasing in transition from IFR to MVFR... and then
from MVFR to VFR. Have backed off category increases slightly from
pvs forecast as stratus tends to linger in a setup like this.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Cogil
LONG TERM...Cogil
AVIATION...Kotenberg


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