Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 150842

Area Forecast Discussion
National Weather Service Aberdeen SD
342 AM CDT Thu Mar 15 2018

.SHORT TERM...(Today through Friday Evening)
Issued at 335 AM CDT Thu Mar 15 2018

Precipitation type and amounts late tonight through Friday evening
will be the main forecast concern.

An area of low pressure will strengthen this afternoon over eastern
Colorado. The surface low will slowly cross northern Kansas tonight
with plenty of low level moisture spreading northward into western
and southern South Dakota. Integrated water vapor transport does
suggest Gulf moisture will be associated with this system, which is
why QPF and PWAT values are high. Mean specific humidity at 500 and
700 hPa are over two standard deviations above normal, mainly in
south central SD. Even with SLR around 10:1, six inches of snow is
possible along I-90 in this CWA. With freezing rain prior to the
heavy wet snow, travel conditions in central SD will be difficult
Friday morning. Will issue a winter storm watch for the potential
for ice and heavy snow. Minor ice accumulation, along with the
potential for 2 to 4 inches of snow, will issue a winter weather
advisory for Sully to Hand County and points south. Pierre is
included in the winter weather advisory.

Little to no precipitation is expected in northeastern SD and
western MN due to dry air. The system will depart the region Friday
evening, leaving behind low clouds and the potential for freezing

.LONG TERM...(Saturday through Wednesday)
Issued at 335 AM CDT Thu Mar 15 2018

The main forecast challenge in the extended is the system slated for
Sun night into Tuesday morning. All models agree on a sfc low track
through Kansas, and all models agree that at least some of the
moisture and enhanced forcing within the upper trough will be
focused in South Dakota. However, differences emerge in timing with
the GFS onset being quicker than the Canadian and EC and in
potential precip amounts. Again, the GFS exhibits as the wettest
model and a significant outlier. Still, this system will be the best
chance for widespread precip in the extended.

By midweek, conditions are forecast to be drier and warmer as an
upper ridge shifts into the Plains.


.AVIATION...(For the 06Z TAFS through 06Z Thursday Night)
Issued at 1254 AM CDT Thu Mar 15 2018

With a light east-northeast wind continuing, expecting a couple of
areas of potential fog development over the next few hours where
said wind is a terrain-influenced upslope wind, with a gradual east
to west migration/expansion. There are some high cirrus clouds over
western and central South Dakota slowly working their way east.
The eastern-most edge of these clouds will end up being the
determining factor for whether or not fog will form. For the time
being, guidance suggests KABR (and perhaps maybe KATY) has the
greatest probability of seeing sub-VFR fog or low clouds between
now and appx 15/16Z on Thursday. Since the cirrus clouds are over
the KMBG/KPIR terminals now, have them staying VFR for the whole
TAF valid period.


SD...Winter Storm Watch from late tonight through Friday evening for

     Winter Weather Advisory from 7 AM Friday to 1 AM CDT Saturday
     for SDZ034>037-051.



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