Area Forecast Discussion
Issued by NWS Rapid City, SD

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908
FXUS63 KUNR 202024
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
224 PM MDT Thu Apr 20 2017

.SHORT TERM...(This Evening Through Friday Night)
Issued at 222 PM MDT Thu Apr 20 2017

Current surface analysis shows an area of low pressure over the
Great Lakes region with high pressure centered over eastern Wyoming
and the western Dakotas. Upper level analysis has a ridge over the
northern plains with a trough extending down the west side of the
Rockies. Skies are mostly clear with a few high clouds making their
way into northeastern Wyoming and southwestern South Dakota. High
temps so far today have reached into the 50s to low 60s. Winds have
begun to diminish and are from the north and east at speeds of 5 to
15 mph.

Clouds will increase from the west tonight as the next system
crosses the Rockies. Latest models are in fairly good agreement with
precipitation chances staying confined to northeastern Wyoming and
far southwestern South Dakota through Friday night/Saturday. Showers
will begin later tonight across northeastern Wyoming, reaching into
parts of southwestern South Dakota by morning. East-southeast winds
will expand across the rest of the forecast area tonight, possibly
allowing patchy fog to develop from the Black Hills eastward late
tonight into early Friday. Low temperatures overnight will be in the
30s.

Chances for showers will persist across northeastern Wyoming and
into the Black Hills and far southwestern South Dakota on Friday.
Some light snow could mix in with any showers early Friday,
especially over the higher elevations in the hills. Skies will be
mostly cloudy across much of the area on Friday, with the most sun
expected toward northwestern and central South Dakota. Highs will
range from the upper 40s to mid 50s across northeastern Wyoming and
the Black Hills to the upper 50s to around 60 over northwest to
central South Dakota. Showers will linger Friday night, mainly
across northeast Wyoming.

.LONG TERM...(Saturday Through Thursday)
Issued at 222 PM MDT Thu Apr 20 2017

A few showers will likely stick around into Saturday morning across
northeast Wyoming and possibly the Black Hills before high pressure
builds in and pushes the lingering energy out of the area. An upper
ridge will set-up across the western CONUS for the weekend, allowing
warmer and drier conditions to return. Highs on Saturday should
reach into the mid 50s to mid 60s with even warmer conditions on
Sunday when highs reach into the upper 60s to mid 70s.

Next week looks to be on the cool side with daily chances for
showers. Overall, high temperatures will be near average early in
the week, dropping below average mid to late week. Models are
beginning to show an upper low crossing the northern plains late in
the week, possibly bringing significant precipitation. Colder air
with this system could bring some overnight/morning snow depending
on the timing.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 222 PM MDT Thu Apr 20 2017

Areas of MVFR CIGS will continue over parts of northwestern South
Dakota through this evening. Scattered -SHRASN with areas of MVFR
cigs are expected over northeastern Wyoming and parts of far
western South Dakota tonight and Friday morning. Areas of IFR cigs
in stratus and fog are expected over the rest of western South
Dakota late tonight/early Friday.

&&

.FIRE WEATHER...
Issued at 222 PM MDT Thu Apr 20 2017

Green-up appears to be in full swing as the vegetation condition
comparison for mid April indicates the entire forecast area has
increased vegetation for this time of the year. However, high
temperatures on Sunday in the upper 60s to mid 70s combined with
gusty southerly winds and minimum relative humidity values of 20 to
25 percent may result in some fire weather concerns.

&&

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

$$

SHORT TERM...MLS
LONG TERM...MLS
AVIATION...10
FIRE WEATHER...MLS



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