Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 132010

Area Forecast Discussion
National Weather Service Aberdeen SD
310 PM CDT Fri Apr 13 2018

.SHORT TERM...(This Evening through Saturday)
Issued at 309 PM CDT Fri Apr 13 2018

A strong storm will continue to exit the Rockies and move into the
plains through tonight and Saturday. Waves of energy are expected to
rotate around the developing upper low and across the region through
Saturday. The precipitation across western South Dakota will likely
be on the downward trend this evening, as the emphasis shifts to the
east overnight. The current frontogenetic band from Miller
northeast toward Ortonville may persist for another couple
hours but then should start to dissipate as WAA slackens some.
Meanwhile, theta-e advection will continue across central and into
eastern South Dakota through tonight on north side of developing
upper low. A couple of trowal features are progged to rotate into
eastern South Dakota, thus maintaining a couple different bands of
pcpn over the next 12 to 18 hours.  It appears from model data that
the best UVM/moisture will exist over the southern half of the
state, and this is where the heaviest snow should fall. Further
north the northerly boundary layer flow is bringing in drier air,
the airmass north of the border features dewpoints generally in the
teens.  That relatively dry air is headed south and is seemingly
choking the pcpn bands as they get close to the northern counties.
Because of this, a few counties have been dropped back to an advisory
vs blizzard warning. Will maintain a blizzard warning for much of
the southern CWA given expected snowfall and wind through tonight
and into Saturday. A cold airmass overall will continue across
the eastern half of the state through the weekend, with below normal
temperatures expected.

.LONG TERM...(Saturday Night through Friday)
Issued at 309 PM CDT Fri Apr 13 2018

Very progressive pattern continues through this extended period,
marked by change. By 00Z Sunday the 500mb low will be over the
NE/IA/MO border. This feature will slowly slide east across IA/MO
through the day. With the sfc ridge sliding into central SD, expect
the best chance for a clear/cold morning there, with temperatures
falling into the low teens. A few single digit lows will not be out
of the question. The ridge will slowly slide across the rest of the
cwa during the day Sunday, and exit into MN Monday afternoon. Expect
the 500mb ridge currently over the western states to build across
the Northern Plains Sunday night-Monday. With the high at the sfc
and aloft, expect dry conditions to persist. Winds will increase
Monday afternoon over our western counties, with gusts nearing 25-
30kts. On a positive note fire wise, humidity should also be

The pressure gradient will continue to increase Monday night into
Tuesday, with an elongated area of low pressure stretching from far
southeastern Alberta through eastern MT/far southwestern SD and
western KS by daybreak Tuesday. The latest thought is that the
southern end of this trough will intensify and eject east across
NE/KS through the day Tuesday. Expecting mainly rain over our area,
transitioning to light snow Tuesday night into early Wednesday east.
With plenty of warm air to overcome, SLRs are expected to be 10:1 or
less. The next 500mb low over the MT/Canadian border Tuesday
afternoon looks to slide southeast across our area Tuesday night,
with the sfc low intensifying near IA. Look for a ridge to
temporarily build in Thursday-Thursday night, ahead of another low
nearing from the 4-corners region Friday. At this point, the
consensus is for the sfc low to track across KS/OK Friday night,
with some precipitation possible across our area.


.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1217 PM CDT Fri Apr 13 2018

Most of the precipitation has been able to transition to snow,
slowest to slide into ABR and ATY. HON has been reporting reduced
vis in fog, and some earlier snow. MBG is at the tail end of the
worst conditions, as they shift southeast. ABR is the trickiest
site, where MVFR hover over or just south of the airport through
02Z. Still expect periods of IFR, mainly at PIR and ATY with
blowing snow with gusts of 30 to near 40kts. Look for VFR ceilings
and winds around 20kts or less to return by late Saturday morning.


SD...Winter Weather Advisory until 7 AM CDT /6 AM MDT/ Saturday for

     Blizzard Warning until 7 PM CDT Saturday for SDZ008-011-018>023.

     Winter Weather Advisory until 1 PM CDT Saturday for SDZ005-006-

     Winter Weather Advisory until 7 PM CDT Saturday for SDZ007.

     Blizzard Warning until 7 AM CDT /6 AM MDT/ Saturday for SDZ015-

     Blizzard Warning until 1 PM CDT Saturday for SDZ017-036-037-051.

MN...Blizzard Warning until 7 PM CDT Saturday for MNZ039-046.



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