Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 112150
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
350 PM CST Wed Jan 11 2017

.SHORT TERM.../Tonight through Thursday/
Issued at 350 PM CST Wed Jan 11 2017

Main concerns will be temperatures and precipitation through the
period. Subjective sfc analysis shows Arctic boundary moving
southeast as high builds into the region today...trend will continue
tonight to have shallow cold air mass moving into northern Missouri.
Along with the cold air filtering into the area...scattered flurries
have been occurring north of the boundary and have added some
flurries into the evening hours over the southern areas of the
forecast area. Though high remains at the surface over the Dakotas
this afternoon it will drift to the east overnight.  Meanwhile there
are a series of shortwaves over the western US which will interact
with boundary. The first will arrive tonight with limited
moisture...but with up to a tenth of an inch of qpf or less and
temperatures quite cold...snow liquid ratios will be pushing 15:1 to
20:1 at times overnight.  This will likely result in a band of 0.5
to 1 inch of snowfall across the north as the upper level reflection
at H850/H500 moves east over the area through 12z. Cold air
advection will continue to push southeast overnight with lows
dropping toward zero north and in the teens south.  By morning the
shortwave will be east of the region with some lingering low clouds
in the north and initially some clearing in the south.  For the
remainder of the day increasing high clouds are expected with the
advance of the next upstream system across the southwest. Highs will
recover into the mid teens north to the lower to mid 20s south.
Otherwise a break from the somewhat active weather is expected until
Friday.

.LONG TERM.../Thursday night through Wednesday/
Issued at 350 PM CST Wed Jan 11 2017

A few different events to look at through the extended with the main
focus on Sunday into early next week. First little impulse pushing
through Iowa Friday to bring some light snow with an area of cold
Canadian high pressure in place. This will send temperatures below
average and wind chills to near advisory criteria early Friday
morning. Temps then gradually warm into the weekend as return flow
sets up. With the push of southerly flow some weak energy ejects
into the central US ahead of the main western upper level trough
digging into the southwestern US late this week. This will bring a
chance for a light wintry mix across the far south into Friday night
and Saturday. Somewhat concerned the moisture won`t make it this far
north, so much of the precip could end up into Missouri.

The main focus then shifts to the large upper trough lifting out of
the desert SW late in the weekend into early next week. Southerly
flow into the state with an inverted surface trough feature to lift
into Iowa Sunday into Sunday night. Cold air still in place at the
surface with warming aloft will lead to a large push of mixed
precipitation across the CWA late Sunday into Sunday night. Many
details still to be ironed out especially with timing/track of the
sfc low and final thermal details. However soundings currently
indicating liquid precipitation across much of the area late Sunday
into Sunday night, with surface temperatures below freezing. Depth
of the cold layer and how fast low level temps warm, could even end
up with a period of sleet given low level temps around -5C could see
some refreeze of the hydrometeor. As the surface low lifts toward
Iowa should have the warm front push north and temps warm above
freezing to have precip changeover to all rain into Monday. Timing
of this changeover continues to be delayed some with the gfs/ec
digging the system a bit more suggesting a longer potential of
wintry mixed precipitation at this time. The upper low then lifts
through the state into Tuesday with colder air in place which could
lead to some light snow chances on the backside of this system.
Early projections on QPF and any wintry precip accumulations are
suggesting light ice/snow accumulations possible across far northern
IA with light to moderate ice accumulations across central and
southern IA mainly south of HWY 30. This has the potential to be a
decent icing event, and the forecast should be monitored closely
over the coming days as more details become certain into Friday and
early this weekend. Please pay attention if you have any travel
plans across IA and especially into areas to the west and south
regarding icing potential as well.

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1133 AM CST Wed Jan 11 2017

Main concerns are cigs...winds and ptype. 10 to 20 kt winds and
lower cigs are developing immediately behind the boundary through
01z as it passes southeast of area. Saturation has not been realized
though better chances yet through 23z at KALO so with low confidence
will continue VCSH for light precip there. Otherwise light snow
expected over northern Iowa aft 06z with KFOD...KMCW... and KALO
possibly being affected through 13z. Some reduction in vsby to
MVFR also expected at these sites.


&&

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

&&

$$

SHORT TERM...REV
LONG TERM...Beerends
AVIATION...REV



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