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Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
529 PM MDT Wed Oct 23 2019

Discussion...(this evening through wednesday)
issued at 201 PM MDT Wed Oct 23 2019

Mean northwest flow will continue through the forecast period. Departing
clipper system will support lingering rain and snow showers over
southern South Dakota through afternoon, while continued northwest moist
flow will support rounds of weak upslope snow into Thursday
morning. Expect an additional 1-2 inches of snow in the northern
Black Hills through the night. Lingering flurries or light snow
can be expected in the northern Black Hills and the northwest South Dakota plains
Thursday morning as a band of stratocumulus pushes east across the
region. Drier air will begin to push into the forecast area with clearing
over the western half expected by afternoon. Cool temperatures can
be expected with highs in the 30s and 40s, 20s in parts of the
high Black Hills. A very deep Aleutian low will then support
massive ridging into Alaska and northwest Canada, shifting a mean deep
trough east and dislodging a large portion of modified Arctic air
southeast into the Continental U.S.. ahead of the associated low pressure system
will be dry westerly downslope flow, which will support a very
nice fall day Friday, with 60s expected for highs over much of the
fa, maybe even a few 70s where deeper mixing occurs. However,
system associated cold front will arrive Sat, with forecast models
continuing to speed this front up, typical of strong cp
air masses. There will likely be a band of rain/snow that will
shift south across the region, with the best chance of snow
expected across the western third of the fa, esp NE Wyoming where some
accums are likely. Main upper trough will dig far south into the
SW Continental U.S. With mean troughing expected over the region the first
part of the week. This swill support unsettled and very cold
conditions (for the date) with mean gefs and naefs ensembles
indicating min or near min percentiles for 700 mb temps in the Monday-
tues period. Mean ridging then looks on track for the remainder
of the week with a slow warming trend.

&&

Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 527 PM MDT Wed Oct 23 2019

Scattered snow showers with IFR/local LIFR conditions will wane
this evening, ending Thursday morning. Outside of the snow
showers, areas MVFR ceilings expected through Thursday morning. VFR
conditions then expected Thursday afternoon.

&&

Unr watches/warnings/advisories...
South Dakota...none.
Wyoming...none.
&&

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