Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 181706

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1106 AM MDT Sat Mar 18 2017

.SHORT TERM...(Today Through Sunday Night)
Issued at 224 AM MDT Sat Mar 18 2017

Strong upper trough will push into the northern plains and
support shortwave ridging into the region today. WAA per downslope
Rockies flow will support much warmer conds most places. However,
ongoing pressure falls will support SE flow over most of western
SD and will fight the breakdown of the growing temp inversion
aloft, slowing warming to a degree esp the NE zones. Hence, expect
a range of highs from lower 60s east to the upper 70s west
(warmest where flow turns SW, NE WY and far SW SD). Lee side
trough will shift east overnight tonight, supporting very mild
temps, esp in the lee of the Black Hills where downward flow
transport will continue to mix down warm air aloft. Main upper
trough will shift east across southern Canada, supporting a cold
front south into the FA Sunday, in a stalling fashion. Northern
areas will see much cooler temps, while scentral SD will see highs
in the upper 70s. Increasing ll moisture, steep lapse rates aloft
and BH elevated heating will support shra (possibly some thunder)
Sunday afternoon, with weak elevated FGEN possibly supporting a
few passing high based showers from NE WY into NW SD. Shower
chances will linger and spread east Sunday night as several weak
impulses shift east in westerly flow.

.LONG TERM...(Monday Through Friday)
Issued at 224 AM MDT Sat Mar 18 2017

Flow will remain progressive, but will become more amplified next
week. A stronger upper trough will affect the region Monday
night, with rain and snow likely over most of the area, esp the SW
half. Some light accums will be possible as enough cold air will
be in place. Unsettled and near seasonal to slightly above
seasonal temps expected much of next week, with periodic chances
for rain and snow showers and breezy conds. ECMWF/GFS progs
continue to suggest a stronger system will affect the region
toward Thur-Fri next week, with perhaps appreciable precip for a
portion of the FA, esp if the upper trough trends NW, which it now
has. Warm thermal fields continue to suggest mainly rain with
this system.


.AVIATION...(For the 18Z TAFS Through 18Z Sunday)
Issued At 1104 AM MDT Sat Mar 18 2017

VFR conditions will continue through Sunday morning. Gusty
southerly winds will develop shortly and continue through tonight
over northeast WY. A trough will push into the region tonight,
support LLWS over western SD where boundary layer decoupling
occurs. Gusty southwest to west winds may occur on the eastern
slopes of the Black Hills later tonight.


Issued At 224 AM MDT Sat Mar 18 2017

Warm dry westerly flow will support critical to near critical fire
weather conditions this afternoon over portions of NE WY. RH is
expected to drop to 10-20 percent there. Winds will shift SW over
Campbell county and become sustained at 20 to 30 mph. Have decided
to issue a red flag warning for all of Campbell county where the
strongest winds and deepest mixing are expected. Hires models do
suggest that the dry line will shift into far western Crook and
Weston counties, with a small window for red flag conds possible
there, although not widespread enough or long enough for


WY...Red Flag Warning until 7 PM MDT this evening for WYZ259-297.



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