Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 181730

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1030 AM MST Mon Dec 18 2017

.DISCUSSION...(Today Through Sunday)
Issued at 322 AM MST Mon Dec 18 2017

Low amplitude ridging sits across the much of the western CONUS and
is building into the region. Warmer air is advecting into the
northern plains, which will bring much warmer temperatures to the
CWA than yesterday. Highs will reach the upper 30s and 40s across
northeast Wyoming and the Black Hills, while temps reach the 50s
across the western SD plains. A series of waves pushing across the
west/northwest flow will weaken the ridge late today into tonight,
bringing a cold front to the area. This frontal passage may see some
light rain or snow develop along the initial boundary push across far
northwest SD, but this will be short lived this evening. Precip is
not expected across the rest of the CWA. Frontal boundary will stall
across the area Tuesday and Wednesday with a wide range of max temps
both days. Highs across northwest SD will be in the upper 30s both
days while southwest SD will see highs in the upper 40s Tuesday and
upper 50s Wednesday. Deep upper trough is still progged to cross the
western CONUS Wednesday into Thursday with a surface low pushing
across Wednesday. The surface low will depart Wednesday, while a
secondary low develops across the central Plains. Large scale ascent
will bring a widespread area of snow Wednesday night into Thursday.
Models have been trending slightly upward with expected snow
amounts, now reaching into the 2 to 4 inch range. Will continue to
keep an eye on model trends. Highs Thursday into Friday will be in
the teens and 20s, but then the next cold front late Friday will
bring continued chances of light snow along with much colder
temperatures through the end of the week. Highs during this period
could be in the single digits and teens.


.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1028 AM MST Mon Dec 18 2017

There is a slight chance of rain or snow over far northwest South
Dakota this evening with local MVFR conditions. Otherwise, VFR
conditions expected across the area through Tuesday morning.




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