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
FXUS63 KUNR 061634

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
934 AM MST Wed Dec 6 2017

Issued at 934 AM MST Wed Dec 6 2017

Current surface analysis shows a Canadian cold front sliding south
across the forecast area. Upper level analysis shows low pressure
over southern Hudson Bay, with large trough covering a good
portion of the US. A ridge lies along the west coast. The passing
front is bringing another round of gusty winds and areas of
snowfall. Upslope enhanced snowfall continues across the northern
Black Hills. A relatively narrow band of light to moderate snow
accompanying the front stretches from north of the Black Hills to
parts of south central SD, moving generally to the south-
southeast. A quick half inch to inch of snowfall is likely with
the band as it moves through west central and southern SD through
the early afternoon. Temps currently range from the upper teens
across northwest SD to around freezing over far southwest SD.
Temps will generally remain nearly steady or slowly fall through
the day in most areas as colder air pushes in. The gusty winds
will persist through much of the afternoon, gradually tapering off
around sunset.

Have made minor adjustments to the forecast through the afternoon,
mainly raising pops and adding some blowing snow potential across
the area with the band of snow pushing through the next few
hours. Current headlines look OK at this time.


.DISCUSSION...(Today Through Tuesday)
Issued at 334 AM MST Wed Dec 6 2017

Upper level analysis has highly amplified flow with large trof
across the central and eastern CONUS, and sharp ridge along the
West Coast. Fast northerly flow continues over the Northern
Plains. Skies are cloudy across the Northern Plains, with next
upper shortwave dropping south across the forecast area at the
moment. Light snow is on the increase. At the surface, weak
clipper system is dropping south through the Dakotas at the
moment. Temperatures are mainly in the 20s and lower 30s. Winds
are out of the northwest at 20 to 35 mph with gusts to 45 mph.

Clipper system and associated cold front will drop south through
the forecast area this morning, bringing continued light snow for
much of the area, along with gusty northwest winds. A wind
advisory is in effect for much of the SD plains through this
afternoon. Not expecting much more than an inch of snowfall across
the plains today, but with the winds and some previous snow on the
ground, there will be some areas of reduced visibility with
blowing and drifting snow. Across the Black Hills, upslope
enhanced snow will produce accumulations of 4 to 6 inches, with
locally 8 inches expected. A Winter Weather Advisory continues
across this area through 11pm tonight. Temperatures will remain
below average today, with highs only expected in the upper 20s to
lower 30s. Light snow will end early this evening as the clipper
system shifts southeast, and skies will become partly to mostly
cloudy. A cold night is on tap, with lows mainly in the teens.

Strong north to northwest flow will persist through Friday as the
main upper trof sets up across the eastern CONUS, and the West
Coast ridge builds into the Great Basin area. North to northwest
winds will stay windy during the daytime hours for the next
couple of days, and there will be decreasing chances for light
snow over the northern Black Hills on Thursday. Towards the end
of the week, a gradual warming and drying trend is expected as the
western upper ridge shifts eastward.


.AVIATION...(For the 12Z TAFS Through 12Z Thursday Morning)
Issued At 411 AM MST Wed Dec 6 2017

A series of disturbances will move through the region in the next
24 hours, bringing some snow and flight restrictions to parts of
the region. An arctic front will push back to the west and
support snow showers over much of the area today, especially the
northern Black Hills. Expect flight conditions to trend lower with
MVFR/IFR over much of the area this morning thorugh afternoon. Local
LIFR conditions are expected around the Black Hills and northeast
Wyoming. It will also be windy across most of the area with gusty
northwest winds.


SD...Winter Weather Advisory until 11 PM MST this evening for SDZ024-

     Wind Advisory until 5 PM MST this afternoon for SDZ001-002-

WY...Winter Weather Advisory until 11 PM MST this evening for WYZ057.



AVIATION...7 is the U.S. government's official web portal to all federal, state and local government web resources and services.