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Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
459 PM MDT sun Apr 30 2017

Discussion...(this evening through sunday)
issued at 159 PM MDT sun Apr 30 2017

Mean troughing will continue over the region through mid next
week with a few systems bringing chances for precip. Deep closed
low over the Southern Plains will slowly progress east/northeast.
Precip shield from the this system continues to try and shift northwest
into the forecast area. However, very dry air in the ll/S continues to fight
top down saturation with precip drying up over far eastern
scentral South Dakota. Have cut pops there trough tonight, with only a very
slight chance mention retained for the southeast half of trip County.
Attention turns to the next system which will impact the region
tonight into Monday. Sat trends indicate a cu field over southeast Montana and
hrrr has consistently indicated a few shra over northern Campbell
County late this afternoon, although dry air in the ll's will
again fight any showers, with virga more likely. Pac system will
advect into the region tonight and may support a few rain/snow
shra over the western half in a weak fgen regime. Better chances
(although not great) for precip will arrive Monday afternoon. The
associated cold pool from this system will support steep ll lapse
rates Monday afternoon, generating some small cape over the
region, enough to support a few showers perhaps a few ts, esp
across northwest South Dakota. It will also be quite breezy Monday given strong
linked flow aloft and expected deep mixing, windiest across northwest South Dakota
where adv winds are expected. Have added northwest South Dakota to a wind adv for
this where sustained winds of 25 to 35 mph with gusts to 50 mph
are expected, esp in/near any convective shra. A stronger system
will then arrive tues, supporting a decent chance for rain showers
and possibly a ts, esp across the SW half. A few snow showers
will also be possible tues evening above 6 kft with any lingering
activity.

After tues, the pattern begins to shift with massive ridging
progged over the western Continental U.S.. this will support much warmer
conds and dry weather the remainder of the week, with 70s and 80s
expected toward the end of next week. Forecast models are progging
another large closed low over the West Coast next weekend, which
would sustain the ridge in place into next week, keeping conds
quite warm here.

&&

Aviation...(for the 00z tafs through 00z Monday evening)
issued at 456 PM MDT sun Apr 30 2017

VFR conditions are expected for most areas through the period. The
exception will be for some MVFR conditions with showers that move
through the Black Hills area from 09-16z, with perhaps spotty MVFR
conditions across northeastern Wyoming during the same time. This will
be in association with a weak storm system that passes through
the area late tonight and Monday. Also with this storm will be
gusty northwest winds of 30-45 kt for most areas on Monday.

&&

Unr watches/warnings/advisories...
South Dakota...Wind Advisory from 10 am to 7 PM MDT Monday for sdz001-002-012-
013-025-026-031-072-073.

Wyoming...none.
&&

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