Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 182337 AAA

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
637 PM CDT Sun Mar 18 2018

Issued at 632 PM CDT Sun Mar 18 2018

See updated aviation discussion below.


.SHORT TERM...(This Evening through Monday)
Issued at 328 PM CDT Sun Mar 18 2018

A system currently over the Rockies will move out into the plains
overnight and through Monday. The strongest chunk of energy moves
east across the Central/Southern Plains, but weak energy evident in
the tropopause charts does track across the region. And for the most
part, it appears the atmosphere will saturate pretty thoroughly
as the system tracks east through Monday. Soundings/critical
thickness progs indicate that once pcpn gets started, any warm
layer aloft should get obliterated. So, despite there being
perhaps a very small window of possible mixed pcpn, me and my
neighbors decided to go all snow/rain. Snow/QPF amounts have
trended up a notch across the region, so it now appears a 36 hour
event featuring 1 to locally 3 inches of snow appears possible.
Given all the clouds and some fog overnight, temperatures should
stay relatively mild. Monday should see temperatures near to just
above freezing. The light snow should continue into Monday night.

.LONG TERM...(Monday Night through Sunday)
Issued at 328 PM CDT Sun Mar 18 2018

We`ll still be under an active pattern at 500mb, with a weak trough
over central SD and NE. Precipitation lingers on north winds over
our eastern counties, as the trough (plus inverted sfc trough)slowly
exits to our east shortly after daybreak Tuesday. Only expecting a
brief break in the clouds, and potentially precipitation, as a
deeper trough swings in from the northwest during the day Tuesday.
Not a lot of moisture with that one though, so slight chance pops or
less look good.

The 500mb ridge over the western third of the nation Tuesday night-
Wednesday, will build over the Plains States Thursday-Thursday
night. While warmer and drier weather looks to be the rule, with
near to above normal temperatures, we will be tracking the deepening
low off the west coast. This feature will act to suppress the ridge
over the Plains for the end of the week, and bring a couple round of
precipitation. The first round looks to swing into central SD
Thursday evening, in the form of rain. Breezy southeast winds will
also be common Thursday night through much of Friday. The best
chance of snow will be along the ND/SD border, before precipitation
ends Friday afternoon/evening as the lee trough to our west
Friday morning shifts across the Plains and nearly to the Ohio
River Valley by 12Z Saturday. While the GFS is on the
quicker/weaker side, the Canadian is stronger/slower, with the
ECMWF in between.

Uncertainty increases significantly as we move into Saturday
evening, with the focus in different areas of the forecast area, as
the coastal low opens up and drifts either to the Intermountain West
or Northern Plains.


.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 632 PM CDT Sun Mar 18 2018

IFR/MVFR cigs will remain in place over the CWA through the TAF
period. Precipitation is expected to spread from west to east
across the area from later this evening through the day Monday.
The precipitation will vary from snow to rain depending on
temperatures, with vsbys likely falling into the MVFR category at




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