Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 200442

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1042 PM MDT Thu Oct 19 2017

.DISCUSSION...(This Evening Through Thursday)
Issued at 240 PM MDT Thu Oct 19 2017

Broad upper ridge covers much of the CONUS, with mostly sunny to
partly cloudy skies over the northern plains. At the surface, weak
lee trof extends across Montana into northeast Wyoming and western
South Dakota. Southwesterly winds are generally around 10-15 kts,
and some areas are gusting to 25-35 kts. Temperatures at 3 PM are
in the mid 70s to mid 80s.

Very warm and dry weather will continue into Friday, with highs
in the mid 70s to mid 80s again. Some locations may come close to
records on Friday. Southwesterly winds will be gusty again across
northeastern WY into western SD.

An upper level trof will cross the Rockies Friday night with a
strong cold front moving through the northern Plains. West to
northwest winds will be gusty Friday night at 20 to 35 mph with
higher gusts. South central SD may see some light rain showers
Friday night into Saturday, but most places will remain dry.
Northwest winds will become strong again on Saturday, especially
across northwestern SD, and highs will cool to the 50s and lower
60s. Sunday will be dry and warmer as upper ridging builds behind
the trof. However, a fast-moving wave Sunday night could bring
another chance for light rain/snow to the area into Monday. Models
are still showing another upper ridge building over the west
coast early to mid week; however, towards the end of next week the
ridge breaks down and another upper wave moves through the
northern Plains, with potentially much cooler air.


.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1039 PM MDT Thu Oct 19 2017

VFR conditions will continue through the period. Gusty south-
southwest winds will continue tonight across northeast Wyoming.
Low level wind shear is expected across the plains of far
southwestern and south central South Dakota tonight. Expect gusty
SW winds most places Friday. A strong cold front will push into
the region, with winds veering NW and becoming gusty for period.
ISOLD TS will be possible ahead of the front Fri evening across
scentral SD.


Issued At 240 PM MDT Thu Oct 19 2017

Minimum RH will be very low again on Friday, ranging from 15%
across northeastern WY to 25% across much of western SD. Gusty
southwest winds are expected to re-develop across northeastern
WY, as well as the Black Hills and northwest South Dakota Friday
afternoon. With low RH and frequent gusts of 25+ mph across
this area, and a strong cold frontal passage Friday evening, have
issued another Red Flag Warning for Friday afternoon and evening.


SD...Red Flag Warning from noon Friday to midnight MDT Friday night
     for SDZ260>262.

WY...Red Flag Warning from noon Friday to midnight MDT Friday night
     for WYZ259-297>299.



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