Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 151745

Area Forecast Discussion
National Weather Service Aberdeen SD
1245 PM CDT Thu Mar 15 2018

Issued at 1230 PM CDT Thu Mar 15 2018

No real changes in the short term. Focus remains on the system for
Friday. Initial troughs support slowing down onset timing given
shallow dry fetch in NAM BUFKIT soundings which will eliminate any
potential for pre-event drizzle. Profiles do show a warm layer,
maybe deep enough to initially see rain, but a quick cool down
will change precipitation type to sleet and then snow, after which
we are stuck with snow profiles until loss of ice in the
dendritic growth zone and stuck under thick stratus which will
result in a period of light drizzle/sprinkles through early
Saturday morning.


.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 18Z TAFS through 18Z Friday Afternoon)
Issued at 1230 PM CDT Thu Mar 15 2018

VFR conditions will become IFR for KPIR Friday with a system
moving in that will generate heavy snow. Much less certain where
the categories will lay, between IFR/MVFR potentially for KATY
close to the end of the TAF 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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