Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 120457

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1057 PM MDT Sun Mar 11 2018

.DISCUSSION...(This Evening Through Sunday)
Issued at 246 PM MDT Sun Mar 11 2018

Current surface analysis shows high pressure centered over the
western Dakotas, with clear skies and light winds across the area.
Upper level analysis shows shortwave ridge over the high plains,
with a weak shortwave over ID and western MT. Temps are in the 30s
across much of the area, with some lower 40s over portions of
northeast WY and southwest SD.

Upper level ridging will dominate the weather over the next several
days, with a significant warming trend in most areas by midweek. For
tonight, there could be patchy fog from far northeast WY into
northwest and central SD, especially in valley locations. Lows will
mostly be in the teens, with some 20s over parts of northeast WY.
The weak shortwave to the west will pass mostly to the southwest of
the area on Monday, with just some mid and high clouds pushing
across western and southern portions of the CWA. Highs on Monday
will be in the mid 30s to upper 40s. Ridge builds even stronger
across the Rockies behind exiting wave, with highs well above
average in most areas for Wednesday and Thursday. We are looking at
highs in the 50s and 60s for most areas, warmest generally across
the southwest SD plains, where a few spots could at least approach
70. Heavier snowpack areas of northwest SD are more likely to stay
in the 40s for highs on those days.

Ridge is forecast to shift east of the region by Friday, with some
cooler air returning behind a passing cold front. Large scale trough
will push into the western US late week, with southwesterly flow
developing behind exiting ridge. This should at least bring a more
unsettled pattern for Friday and the weekend. Models have been very
inconsistent on how this trough will evolve as it moves east through
the Rockies and eventually into the Plains, but at least occasional
chances for rain and snow are looking more likely. Some runs have
been showing the potential for a more significant system to impact
at least portions of the region toward the latter part of the
weekend, but again the run to run consistency between the various
medium range models has been poor to this point.


.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1057 PM MDT Sun Mar 11 2018

Lowered vsbys due to FG/BR may develop tonight within low-lying
areas of the SD plains. Otherwise, conditions will remain VFR
across the area through Monday afternoon. Monday night, light
upslope flow may again lead to some FG/BR development over the SD
plains and on the east side of the Black Hills after 00z.




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