Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 192001

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
201 PM MDT Mon Mar 19 2018

.DISCUSSION...(This Evening Through Monday)
Issued at 159 PM MDT Mon Mar 19 2018

Broad trough over the region aloft will continue to shift east
tonight. Dry air has advected into the region with drizzle/snow
ending over the western 2/3. Light snow will continue over
scentral SD into this evening, waning toward late evening. Some
freezing drizzle will also be possible there as the mid levels dry
and the low levels remain saturated for a bit with lingering low
level lift. Some patchy fog will also be possible over the SD
plains late tonight. Otherwise, another backside compact impulse
many support a few snow showers across NE WY and then NW SD late
tonight into Tue morning, with some isolated snow showers possible
further south into western SD. Diurnal heating under a lingering
cold pool will support some slight chances for rain/snow showers
from the BH southeast Tue afternoon. Dry weather will prevail Wed
as upper level ridging commences.

Western CONUS trough re-loading will occur toward the end of the
week with local WAA and height rises. This will likely support WAA
rain/snow Thur night (with chances shifting NE in this period).
Deep western CONUS trough will eventually shift east this
weekend, with precip chances increasing across the Northern
Plains, possibly supporting a decent storm system if the trough
ejects in large wave packets.

Temperatures will remain around or below seasonal norms for the
next few days, heavily influenced by the snow pack in place on the
SD plains and lack of sig deep southerly flow. Decent melting
should occur in this period with the warmest temps expected over
the sw third where any snow pack will erode the fastest.


.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1106 AM MDT Mon Mar 19 2018

Conditions will gradually improve from west to east through the
afternoon and evening hours as cigs rise and snow tapers off.
However, far northern and eastern portions of our area may remain
MVFR/IFR through tonight, with lingering low stratus expected. VFR
conditions should prevail at KGCC/KRAP by late this afternoon.

Tonight, some FG/BR may develop, particularly within low-lying
areas. For now, it does not appear that this will significantly impact
TAF sites, though minor reductions to vsbys are possible overnight
into Tuesday morning.




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