Area Forecast Discussion
Issued by NWS Aberdeen, SD
FXUS63 KABR 071213 AAB
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
613 AM CST Wed Dec 7 2016
Issued at 608 AM CST Wed Dec 7 2016
Winter Weather Advisory has been expired on time at 6 AM CST.
However, northwest winds of 15 to 30 mph with gusts of 35 to 40
mph continue early this morning throughout the forecast area, and
KABR 88D reflectivity shows light snow continues (has been all
night) on the west-side of the Prairie Coteau region. Travelers
beware. There are likely still localized areas of poor visibility
in this area of falling and blowing snow this morning, so plan
UPDATE Issued at 529 AM CST Wed Dec 7 2016
See below for an aviation forecast discussion for the 12Z TAFs.
.SHORT TERM...(Today through Friday Afternoon)
Issued at 359 AM CST Wed Dec 7 2016
Still seeing some rather breezy winds across the region, but speeds
have slowly been coming down through the overnight hours. Winter
Weather Advisory was extended to 12Z late last night, and feel it
will be allowed to expire at that time. There will still be windy
conditions and areas of near-surface/surface blowing snow over
portions of the region, but feel there will not be enough
lofting/vsby reductions across a large enough area to warrant any
continuation of headlines.
Arctic air continues to spill into the region with slowly falling
temperatures and wind chills. Parts of the western CWA are getting
close to 25 below zero for wind chills, but feel duration and areal
coverage of those values will prevent any wind chill headlines this
Upslope light snow continues across Clark/Day/Marshall counties
early this morning, and it has been snowing there lightly all night.
Expect this trend to continue through the morning. Will also be
watching another lobe of energy dropping south into the area with
additional chances for light snow later today and tonight over the
eastern CWA. Additional accumulations will be light.
With the arctic high settling over the region by 12Z Friday, there
was a collaborative effort to drop lows several degrees from
SuperBlend for Thursday night. This change was more so confined to
the western CWA where there is much more snow cover.
.LONG TERM...(Friday Evening through Tuesday)
Issued at 359 AM CST Wed Dec 7 2016
Here are the highlights in the out periods:
The extended still shapes up to be anomalously cold, with max
temperatures having trouble getting out of the single digits to
teens. The NAEFS/GEFS E.S.A.T. is beginning to come around to
acknowledging temperatures by middle of next week (middle of
December) being 1 or more standard deviations below climo.
The flow pattern aloft is not overly agitated or highly amplified,
but with a strong/active polar jet stream in play, and plenty of low
to mid level thermal packing across portions of the central and
northern plains, shortwaves moving through this flow pattern will be
very capable of generating light (and in some cases potentially
moderate) snow events.
Right now, focusing attention on the system progged to move through
the country`s mid-section Saturday. The 00Z GEFS and deterministic
GFS/ECMWF and Canadian are all in agreement that precipitation
develops/moves over this cwa by mid-morning Saturday through mid-
evening Saturday. Given the amount of low to mid-level thermal
packing still showing up in the GFS/ECMWF and Canadian, fully
expecting that one or more noteworthy bands of snow will impact some
portion of the CWA. For now, left the somewhat more broadbrushed
guidance precip/snow amounts in the forecast, but fully expecting as
this snow event draws closer there will need to be adjustments made
to precip/snow amounts for banded precipitation. As the previous
shift mentioned, SLR`s during this event will likely be quite high
(potentially 20:1 or greater). Fortunately, at this point, wind
speeds are not progged to be as high as winds speeds/gusts have been
the past couple of days. However, if snow in a 20:1 SLR environment
pans out, it won`t take overly strong winds to pick it up and blow
it around. Just one more thing to consider. As far as precip/snow
amounts go, model guidance suggests generally anywhere from a few
hundredths to as much as a quarter inch of water-equivalent precip
will be possible in this event, including anywhere from as little
as a half inch of snow to as much as 5.5 inches of snow.
.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 529 AM CST Wed Dec 7 2016
Strong west to northwest winds won`t subside across the area until
later tonight, with a steady draw down in speed/gustiness
continuing on Thursday.
There are just a couple of areas of mvfr or worse cigs over the
region (stratus streamers coming off Lake Oahe at KPIR and
terrain-influenced low clouds at KATY). Overall, VFR cigs are
expected for more of the 24 hour TAF valid period than MVFR or
worse cigs are. And, in the absence of falling snow, visbies at
all four terminals are VFR this morning, despite winds continue to
be strong and gusty.
Pockets of light (upslope) snow will likely continue along/over
the western half of the Sisseton Hills region today (VCSH at
KATY?). Elsewhere over the forecast area, conditions should be
dry over terminal airspace during the next 24 hours. One more blob
of light snowfall is expected to extend down as far south as the
I-29 corridor eastward into Minnesota for a few hours mainly
later this evening, but at this point not all that confident that
KATY will see much of this light snow potential.