Area Forecast Discussion
Issued by NWS Rapid City, SD
FXUS63 KUNR 252115
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
315 PM MDT Tue Apr 25 2017
.DISCUSSION...(This Evening Through Tuesday)
Issued at 315 PM MDT Tue Apr 25 2017
Current surface analysis shows low pressure over southeast WY,
with frontal boundary south and west of the forecast area. Upper
level analysis shows low pressure over the Black Hills, starting
to move eastward. Large trough covers the western half of the US.
KUDX radar showing light snow over much of northeast WY, the Black
Hills, and onto the western SD plains. Temps remain steady in the
upper 20s to mid 30s with north-northeast winds in most areas.
Snowfall amounts have generally ranged from 2 to 5 inches over far
northeast WY to the northern Black Hills and adjacent plains.
Amounts of 6 inches or more have been reported over portions of
the Bear Lodge Mts and the Sundance area, with an inch or more of
liquid pcpn in these areas.
The storm system will begin to pull away from the area and weaken
late today and this evening. Light snow will continue to gradually
taper off through the early evening hours. Any additional
accumulations will mainly be less than an inch, so will allow the
warning and advisories to expire at 3 PM. Pcpn will generally be out
of the area by midnight, with skies staying mainly cloudy into the
overnight. There will be some breaks in the clouds toward morning
across western areas. Lows will be in the 20s, with some teens
possible in sheltered and snow covered areas. Would not be surprised
to see patchy valley fog late tonight/early Wednesday.
Wednesday looks to be the dry day of the week as the area will be
between weather systems. Skies will become partly cloudy with high
temperatures in the 40s, some upper 30s across the higher Black
Hills. Winds will be relatively light from the north, except light
and variable across much of northeast WY. Will see some increasing
clouds late Wednesday night with lows in the 20s and lower 30s.
Unsettled weather will return for Thursday through at least the
early part of the weekend. Chances for showers will increase from
the south and west across northeast WY, the Black Hills, and
southwest SD on Thursday, with highs in the 40s and lower 50s. Some
differences are noted between the medium range models on how far
north and east the more significant pcpn will make it into the area
as the system slides down the east slopes of the Northern Rockies.
The latest trends from GFS and EC have been to push pcpn further
north and east compared to yesterday. Will continue to keep the
highest pops over portions of northeast WY into southwest SD
Thursday night into Friday. Temperatures look to be cold enough for
some snowfall overnight into Friday and at least some light
accumulations, especially across the higher elevations of these
The weekend looks mostly decent at this point, but still on the
cooler side, with temps below average. Temps will likely get back to
near average levels early next week, but some unsettled weather
looks to return. Will have chances for showers in most areas each
day, with Tuesday looking to have the better potential right now.
.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1113 AM MDT Tue Apr 25 2017
Widespread IFR/LIFR conditions ongoing across nern WY into
western SD due to snow. Conditions will slowly improve from west
to east late this afternoon and evening as snow ends. MVFR (local
IFR) cigs will hang on most of the night with improving conds late
Wed morning and afternoon.