Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 181131 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
531 AM CST Sun Feb 18 2018

.SHORT TERM...(Today through Monday Afternoon)
Issued at 332 AM CST Sun Feb 18 2018

Warm air advection is currently ongoing over this CWA ahead of an
area of low pressure over northeast Wyoming. With the WAA, light
snow has developed this morning, mainly for locations along the
ND/SD border. Snowfall amounts under a half inch is expected. The
surface low pressure should be located over this CWA during the mid
morning hours with warm temps in our east, while the our west will
see CAA developing. Models continue to suggest the pcpn associated
with this low pressure remaining over North Dakota with little
expected in this CWA. By 18Z, CAA will overtake the CWA with gusty
northerly winds expected.

As one surface low pressure departs the region today, another one
begin impacting western South Dakota late this afternoon. This
system, along with upper level jet support will spread accumulating
into central South Dakota, Pierre area, mainly after 0Z Monday. Snow
should gradually progress northeast through the night with most of
the CWA seeing at least some accumulating by 12Z Monday. The
location of the heaviest snowfall STILL remains unclear at this
time. Consensus suggests the heaviest snowfall of 2 to 4 inches
could occur from Pierre, to Redfield, to Ortonville MN. Additional
light snow will be possible on Monday, but overall amounts should be
low. Several CAMS are suggesting a break on Monday between this
storm system and the second one on Monday night. 24-hour storm total
snowfall yields 3 to 6 inches in central South Dakota, and 1 to 3
elsewhere in our CWA. With a low forecaster confidence in seeing
winter storm criteria snow, will maintain the current watch.

.LONG TERM...(Monday Evening through Saturday)
Issued at 332 AM CST Sun Feb 18 2018

During most of the long term, the models maintain a western conus
trof, with a predominate west to southwest flow across the forecast
area. The main activity during the period will be Monday night into
Tuesday. All models now show a deformation zone forming across the
CWA said time period. Of course individual snow bands are a bit
different among the models, with the GFS now holding onto pcpn the
longest on Tuesday, which is contrary to past runs. Given cold
airmass that will be in place, don`t have much of an issue with
progged QPF amounts of up to a quarter inch. Snow ratios are pretty
high, pushing 20:1 or greater, so 3 to 5 inches of snow appears
appropriate Monday night and Tuesday before the accumulating snows
end. Isolated higher amounts are possible with any heavier bands
that may form.  Temperatures will start the period well below
normal, but then should trend toward normal by week`s end.


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 527 AM CST Sun Feb 18 2018

IFR/MVFR cigs will gradually spread southeast over the region
through the morning and afternoon hours. Snow will be on the
increase this evening and overnight from west to east across the


SD...Winter Storm Watch from this evening through late Monday night
     for SDZ015-033>035-045-048.



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