Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 230536 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1236 AM CDT Fri Mar 23 2018

Issued at 652 PM CDT Thu Mar 22 2018

Delayed onset time of precip this evening by a few hours as radar
returns are currently confined to the Black Hills. Otherwise,
forecast remains on track for the overnight period.


.SHORT TERM...(This Evening through Friday Night)
Issued at 349 PM CDT Thu Mar 22 2018

Much of the fog and lower clouds from earlier today have dissipated,
but patches remain across the CWA. Temps have risen nicely into the
40s for most areas, with 50s showing up over the southwest CWA.
Modest easterly breezes continue over the CWA.

During the overnight hours, clouds and moisture will increase from
the west as the storm system moves in. Winds will increase as well,
and used more of a CONSMOS blend for speeds Friday into Friday
night. Difficult forecast shaping up as the placement of the
rain/snow line will be key in just where the heaviest snow will
fall, along with where the sharp cut-off lies. The far northeast CWA
still appears to be in the coldest air the longest, thus better
chances for heavier accumulating snow. Upgraded this area to a
Winter Storm Warning based on latest guidance and forecast snow
amounts. Further west, went with a Winter Weather Advisory as the
rain/snow line should be setting up somewhere in this area, with
reduced totals and maybe more of an icing potential as well. Bufkit
still continues to show a few hours of moderate freezing rain in the
Watertown area, so edited the grids to include more icing potential
in the Coteau/Glacial Lakes region. Still a bit worried what temps
in the 30s will do for accumulating snowfall during the day in late
March - will really need to get some good snowfall rates and large
flakes to make some accumulations. Believe this will happen for the
far east where temps will be around 34 or 35 degrees. In the
advisory area, temps may be a degree or two warmer closer to the
rain/snow line, so could see more difficulty in accumulations, as
well as a sharper cut-off to the snowfall. Of course, a slight shift
in the rain/snow line, or a longer duration of colder air could mean
higher snow totals in the advisory area. In fact, we do have
accumulations near 7 or 8 inches right along the ND border in
McPherson and Brown counties, although it drops off to as little as
an inch over southern Brown. Due to the lack of areal coverage of
the higher totals, decided on the advisory - and also due to the low
confidence. Overall, a rather difficult forecast since we`re dealing
with differing precip types, temps just above freezing, and a
waffling rain/snow line. Unfortunately, it makes the forecast a
medium to fairly low confidence one. But, current headlines seem to
match all available guidance to the best of their ability.
Adjustments to headlines and snow amounts are certainly possible

.LONG TERM...(Saturday through Thursday)
Issued at 349 PM CDT Thu Mar 22 2018

The extended contains several period of potential precipitation. For
the time being, the bar is set at mostly rain or rain/snow p-types
with each of them. Depending on time of day and surface temps, some
of the "rain" chances could end up turning into freezing rain
chances. POPs show up mainly Saturday night into Sunday and then
again Sunday night through Monday. Deterministic and Ensembles
output indicates temperatures should be running near normal
throughout the period.


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1235 AM CDT Fri Mar 23 2018

A mix of IFR/MVFR/VFR conditions with scattered stratus and fog will
further deteriorate overnight in the west and toward morning in the
east as a spring storm marches across the area on Friday. IFR
conditions are expected to develop from west to east in rain, snow,
and/or freezing rain.


SD...Winter Storm Warning from 10 AM this morning to 7 AM CDT
     Saturday for SDZ007-008-021-023.

     Winter Weather Advisory from 10 AM this morning to 7 AM CDT
     Saturday for SDZ011-019-020-022.

     Winter Weather Advisory from 7 AM this morning to 7 AM CDT
     Saturday for SDZ005-006.

MN...Winter Storm Warning from 10 AM this morning to 7 AM CDT
     Saturday for MNZ039-046.



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