Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 182029

Area Forecast Discussion
National Weather Service Aberdeen SD
329 PM CDT Sun Mar 18 2018

.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 18Z TAFS through 18Z Monday Afternoon)
Issued at 1213 PM CDT Sun Mar 18 2018

Mostly IFR cigs are expected through the period, with some IFR
vsbys possible with fog and snow later tonight, and on Monday.
KPIR/KMBG will see the pcpn first, with KABR/KATY not getting much
snow until Monday.




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