Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 220935
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
235 AM MST Sun Jan 22 2017

.SHORT TERM...(Today Through Monday Night)
Issued at 215 AM MST Sun Jan 22 2017

Water vapor shows weak w/sw flow aloft across the nrn plains with
trof moving onto the west coast. Weak sfc pres gradient and light
winds early this mrng across the cwfa.

Will see some areas of fog this mrng across the region given the
light winds and minimal temp/dp spreads. Otherwise...mostly sunny
skies expected with temps similar to yesterday. S/SW winds
increase tonight across nern WY into the Blkhls as upper ridge
axis shifts overhead.

On Monday, upper trof will begin moving into the Rockies with sfc
low developing over WY/CO and shifting into wrn portions of the
cntrl plains late in the day. Lead impulse could bring some light
snow by aftn mainly to areas north of I-90.

Monday night...Upper trof begins to exit the Rockies with sfc low
deepening over the cntrl plains. Widespread light snow will
develop from nern WY through the Blkhls into nwrn SD with an inch
or two of accumulation by Tuesday morning. Northerly winds will
begin to increase late Monday night and could lead to some blowing
snow.

.LONG TERM...(Tuesday Through Saturday)
Issued at 215 AM MST Sun Jan 22 2017

Long wave trough will be located over the Rockies and high plains
Tuesday morning, then track relatively quickly across the plains
Tuesday and Tuesday night. Still a lot of differences between the
various models with regard to upper low formation, along with
track and timing. GFS continues to be the quickest and furthest
north with a developing low, bringing widespread snowfall across
the area, while the EC is a bit further south and initially slower
with developing snowfall. Latest Canadian run has diverged some
from previous runs and looks to be more of an outlier, along with
the NAM, which is much more open with the trough and splits the
flow. EC may be the most preferable right now, but confidence is
rather low on any particular solution at this point. Will keep the
forecast relatively consistent with previous one and go with
likely pops Tuesday, then have pops decrease from west to east
across the area Tuesday night. Still looks like potential snowfall
of 2 to 6 inches over a good portion of the forecast area from
Monday night through Tuesday evening. Brisk northerly winds
Tuesday into Tuesday night will likely produce some areas of
blowing and drifting snow on the plains, especially east of the
Black Hills.

Beyond this system, relatively quiet weather is likely for the
rest of the week as dry northwesterly flow develops on the east
side of a building ridge over the west coast. Colder than average
temperatures can be expected midweek, with a gradual warmup late
in the week and especially over the weekend as the ridge nudges
eastward.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 215 AM MST Sun Jan 22 2017

Patchy IFR/LIFR conditions will linger over the area this
morning, especially over northeast WY and into the southwest SD
plains. Otherwise, VFR conditions can be expected today into
tonight.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

SHORT TERM...Johnson
LONG TERM...26
AVIATION...26


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