Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 170520 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1120 PM CST Fri Feb 16 2018

Issued at 526 PM CST Fri Feb 16 2018

Forecast is on track this evening. No major changes are planned.


.SHORT TERM...(This Evening through Saturday)
Issued at 214 PM CST Fri Feb 16 2018

Forecast challenges tonight and Saturday include temperatures and
snow chances.

Currently, under the effects of some filtered sunshine and 10 to 20
mph southerly winds, temperatures are warming into the teens and
20s. Some parts are warming into the lower 30s this afternoon.

Late tonight (mainly after 09Z), precipitation chances start ramping
up across the far western/northwestern forecast zones as the low
pressure system, as seen in water vapor loop over Montana and Idaho,
trucks on over into the northern plains region. Precipitation
chances (weak forcing/lift) appear to be diminishing as the system
moves toward nern Nebraska and nwrn Iowa late in the day on
Saturday. WPC guidance combined with NationalBlend, SuperBlend, and
ECAM qpf amounts yielded a blanket of generally less than 0.05in of
qpf across the western two-thirds of the CWA between late tonight
and the end of the day Saturday. Factor in snow ratios and the
thermal profile where snow would form/grow for said timeframe and
the result is generally a trace to less than a half inch of snow
potential for tonight/Saturday.

As for temperatures, even though winds shift around to the
west/northwest late tonight into Saturday, and weak caa sets up on
Saturday, the wind direction is a good mixing wind direction. Low
level thermal progs (and increased cloud cover) support temperatures
remaining above normal tonight and near normal on Saturday.

.LONG TERM...(Saturday Night through Friday)
Issued at 214 PM CST Fri Feb 16 2018

The sfc ridge (extending from the high over eastern NE) will quickly
exit into MN Saturday night as low pressure organizes to our west.
The sfc low over northern WY 06-09Z Sunday is expected to move over
southwestern SD before daybreak, with a trough extending to
southeastern SD by 18Z Sunday as the parent low moves across eastern
CO. The 12Z GFS has a deeper/more defined low tracking across the
state (with more instability across ND). There is still plenty of
time for changes with this one. However, light snow/freezing drizzle
look possible along the ND/SD border during the day Sunday.

While the 12z run of the NAM focuses the highest
precipitation/snowfall Monday morning through early Tuesday evening
over our northwestern 4-6 counties, most of the forecast models
highlight our west central to southeastern counties. Will continue
with that theme, and limit the influence of the NAM. Excluding the
NAM, there is impressive consistency has been shown for Sunday night
into Monday morning with the last few model runs, indicating that
our west central to southwestern counties have the best chance of
seeing headline worthy snow totals. Continue to highlight the
potential in the HWO and social media graphics. Expect precipitation
to expand in time, through much of Tuesday, closer to the 12Z ECMWF.
At the current time, based on our latest probabilistic snowfall
experiment graphic, we`re looking at the probability of seeing 6" or
more snow in the 10-30 percent range, except in the 40 percent range
over western Stanley County. Will not be issuing any headlines yet.
However, some (potential Advisory) headlines may be needed for at
least our southwestern counties.

High pressure over MT and western ND Monday afternoon is expected to
sink across western and central SD Tuesday night into Wednesday,
with an extended period of dry weather anticipated Tuesday evening
through at least Thursday evening. No significant changes from the
general model consensus. Expect temperatures to rebound to near
normal for Thursday and Friday of next week.


.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1119 PM CST Fri Feb 16 2018

VFR conditions are expected through the period.




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