Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 221510

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
910 AM MDT SUN MAY 22 2016

Issued at 900 AM MDT Sun May 22 2016

Cold front is moving across western SD...with southeasterly winds
and dewpoints in the 50s/60s ahead of the front, and westerly
winds and 30s/40s dewpoints behind. Clouds are diminishing and
temps are already warming into the 60s. No precip on the radar so
removed PoPs this morning. Since most models are showing precip
over the area now, have little confidence in their forecasts for
this afternoon and evening. Would think storms would be most
likely to develop across central SD this afternoon, along the
front and the area of highest CAPE. However, hi-res convective
models are indicating storms initiating farther west, where there
is better shear but less CAPE. Increased PoPs across northeastern
WY and western SD, but kept highest chances over south central


.SHORT TERM...(Today Through Monday Night)
Issued at 330 AM MDT Sun May 22 2016

Current surface map shows trof/cold front across far eastern
Montana into northeast Wyoming. Convection lifting north out of
northeast Wyoming with isolated shra/tsra developing across south
central South Dakota. Upper low located in southern Alberta with
110kt jet streak lifting across Utah into Wyoming.

For today, cold front slowly slides through western South Dakota
as jet streak shifts into eastern Wyoming/western Dakotas. MLCAPE
of 2000-3000j/kg forecast along cold front, with 25-35m/s bulk
shear. Model reflectivity suggest discrete supercells developing
this afternoon, mainly east of a line from Pine Ridge to Phillip.
Large hail, greater than 2 inches, and damaging winds likely
across south central South Dakota late this afternoon into this
evening. also some potential for tornado development.
Thunderstorms will push east of the forecast area overnight. As
boundary layer flow turns southwest to west behind cold front,
drier air bring a decrease in low clouds across western South
Dakota. With the additional sunshine, high temperatures across
western South Dakota will be warmer than yesterday even with the
passage of the cold front. Dry weather expected for Monday.

.LONG TERM...(Tuesday Through Saturday)
Issued at 330 AM MDT Sun May 22 2016

Mean upper trough over the western CONUS will change little
through much of the upcoming week. Southwest flow aloft will
prevail over the CWA with periodic shortwaves and a couple of
transient upper lows passing through. Hard to pin point timing at
this point, so PoPs generally broad-brushed. The weather does
look unsettled with daily chances for storms Tuesday through next
weekend. Temperatures will be seasonal.


.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 520 AM MDT Sun May 22 2016

Areas of MVFR ceilings will linger across parts of western SD and
NE Wyoming into the morning hours. A weak surface trough over
western SD will push east this morning, with winds becoming
westerly behind it. Ceilings should become VFR across all of NE
Wyoming by mid morning, and across far western SD by late morning.
Thunderstorms are expected to develop over the area this afternoon
and evening, with the strongest storms generally east of the Black
Hills. IFR/MVFR conditions and gusty winds will be possible with
any of the showers and storms.


.UNR Watches/Warnings/Advisories...


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