Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 271128

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
428 AM MST Mon Jan 27 2020

.DISCUSSION...(Today Through Sunday)
Issued at 312 AM MST Mon Jan 27 2020

While the latest model solutions are generally in line with each
other, they are painting a much different picture than solutions
that were presented yesterday at this time.

The latest surface analysis shows high pressure located over the
eastern Dakotas/Nebraska and a surface trough is deepening to the
east of the Rockies in response to an upper trough approaching
from the west. This has resulted in a large area of low stratus
over most of the South Dakota side of the forecast area and parts
of northeastern Wyoming, with patches/areas of fog. Due to the
abundant low level moisture in place over the area, and
frontogenesis along the NW-SE oriented surface boundary, some
precipitation will develop as the upper trough affects the area
later today and tonight. While most of the precipitation is
expected to fall as light snow, there may be some periods of
rain, drizzle or light freezing drizzle. While much of the area
may see some light snow later today and tonight, the best chance
for any accumulation will be over parts of northeastern Wyoming,
the Black Hills and far southwestern South Dakota where the low
and mid-level frontogenesis will be strongest. An inch or two of
snow accumulation is possible in those areas, however due to the
timing, mainly during the afternoon/early evening, the
accumulation will be mainly on grassy surfaces and over the higher
terrain. Most other places will see only a dusting to 1/2 inch as
the system moves eastward across the area tonight.

Slightly warmer weather remains on track for Tuesday and
Wednesday with perhaps a few showers over the higher terrain of
the Black Hills due to diurnally enhanced mixing and a few weak
impulses crossing the area. A better chance for more widespread
showers looks possible on Thursday as a stronger impulse crosses
the region. Overall, mild and unsettled flow will persist through
this week, with very warm temps becoming more likely by the end of
the week as a potent shortwave ridge develops ahead of the next
arctic intrusion.


.AVIATION...(For the 12Z TAFS Through 12Z Tuesday Morning)
Issued At 422 AM MST Mon Jan 27 2020

MVFR/IFR ceilings will continue across the western SD plains and
parts of the northeast WY plains through much of the day, with
stratus briefly leaving the KRAP vicinity during the afternoon.
VFR conditions expected across higher elevations through the
afternoon. A cold front will push through late in the afternoon.
This will bring gusty northwest winds and IFR conditions with
light rain and snow showers across northeast Wyoming and far
western South Dakota through the night.




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