Area Forecast Discussion
Issued by NWS Rapid City, SD

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KUNR 140447

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1047 PM MDT Tue Mar 13 2018

.DISCUSSION...(This Evening Through Tuesday)
Issued at 206 PM MDT Tue Mar 13 2018

Latest upper analysis shows a high amplitude upper ridge over the
Rockies and the high plains. At the surface, most of the great
plains are under the influence of high pressure, creating
southeasterly winds over the forecast are tonight. As a result,
there may be some patchy fog again tonight, especially over the
snow covered areas over northwestern South Dakota.

The upper ridge will be located over the forecast area on
Wednesday, bringing mostly sunny skies and warmer temperatures.

Wednesday night into Friday morning, latest models remain in
decent agreement, now bringing colder air into the region along
the precipitation.

The upper ridge will break down Wednesday night into Thursday as
an upper trough deepens over the northwestern CONUS.
Southeasterly flow aloft will increase in response to pressure
falls ahead of the upper trough. This should setup a band of
upslope stratus and potential light mixed precipitation on the
northwestern SD plains late Wednesday night into Thursday
morning. A sharp temperature gradient is expected again Thursday
afternoon with continued colder temperatures over the snowpack and
residual low clouds. The lead shortwave, some models are showing a
closed upper low, ejects into the central plains Thursday night
into Friday with inverted trough extending northeastward into
southeastern Montana. Models are showing vigorous lift and plenty
of moisture. Temperature profiles aloft indicate a wintry mix of
precipitation is possible. The potential exist for several inches
of snow over parts of northeastern Wyoming, the Black Hills and
southwestern South Dakota due to synoptic scale lift and low
level frontogenesis by midday Friday, as well as some light glaze
due to freezing rain.

Quieter weather is expected Saturday, but then another shortwave
will eject from the upper trough, spinning into an upper low
somewhere near/over the CWA. Another chance for several inches of
snow present with heavy snow not out of the question.


.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 1047 PM MDT Tue Mar 13 2018

Areas of BR/FG will bring MVFR/IFR conditions to portions of the
northwestern SD plains overnight. Some of this BR/FG may linger
through midday Wednesday, but generally, VFR conditions are
expected Wednesday morning through evening across the area.

With weak upslope flow developing over the SD plains Wednesday
night ahead of our next low pressure system, BR/FG will likely
again be an issue. For now, think any impacts to cigs/vsbys at
KRAP will be after 06z Wednesday night.




AVIATION...Sherburn is the U.S. government's official web portal to all federal, state and local government web resources and services.