Area Forecast Discussion
Issued by NWS Rapid City, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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

FXUS63 KUNR 211035

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
335 AM MST Wed Feb 21 2018

.DISCUSSION...(Today Through Tuesday)
Issued at 335 AM MST Wed Feb 21 2018

Current surface analysis shows high pressure centered over
northern NE, with arctic airmass in place across the region. Upper
level analysis shows near zonal flow across the region right now,
with a shortwave trough over the western states and a stronger
trough along the British Columbia coast digging south into the
Pacific NW. Across our area, skies are clear with relatively light
winds. Temps range from zero to 20 below across much of the area,
with sheltered valley locations likely even colder. Wind chill
values are mostly in the 15 below to around 30 below zero range
right now.

Cold weather will stay in the area through late week, though there
will be a gradual moderation in temperatures through the period.
Highs today will rise into the teens across most of the area, though
it will likely be a struggle to the north of the Black Hills. Some
20s can be expected across the northern and eastern slopes of the
Black Hills, as well as parts of northeast WY and far southern SD,
as milder air aloft builds in from the southwest. Winds will be
light south to southwest this morning then become southeasterly in
most areas later today behind exiting high.

Clouds will increase tonight as southwesterly flow aloft develops
ahead of digging western US trough. That will help to keep temps
milder tonight, especially from northeast WY to southern SD. A
shortwave moving out of the trough will bring a good chance for snow
across central and eastern portions of NE and SD on Thursday. The
western edge of the pcpn will likely move across south central SD,
with up to 2 inches of accumulation, higher amounts generally toward
Tripp County.

Otherwise, mainly dry weather is still expected across much of the
area through the weekend. The latest GFS is showing a shortwave that
could bring a chance of snow late Friday and Friday night, but
previous runs of the GFS had it passing south of the area and it is
not supported by most of the other models. Will have some pops over
south central SD Friday night for now, but chances could be expanded
further west in later forecasts. Temperatures by Saturday and Sunday
will be closer to average levels, but significant snowpack in most
areas will limit warming potential for a while, especially across
the plains. Mainly dry weather should continue into the early part
of next week, but we could see a more unsettled pattern returning by
the middle of next week as a large scale trough is forecast to
develop across the western US.


.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 1028 PM MST Tue Feb 20 2018

VFR conditions are expected through Thursday afternoon across
most of the area, including at TAF sites. Patchy low-level smoke
remains possible near the Black Hills overnight due to prescribed
burns from earlier Wednesday.

Near the end of the TAF period, BR/FG will likely develop across
portions of the area due to continued south and southeasterly flow
over widespread snowpack. Confidence is currently low in associated
impacts at TAF sites, but we will need to monitor the potential
for reduced cigs/vsbys after 00z, particularly at KRAP.


SD...Wind Chill Advisory until 9 AM MST /10 AM CST/ this morning for

WY...Wind Chill Advisory until 9 AM MST this morning for WYZ054>058-



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