Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
529 am MDT Tuesday may 21 2013
Short term...today through Wednesday night
issued at 236 am MDT Tuesday may 21 2013
Current surface map places low over eastern South Dakota...with
trough extending west through western South Dakota. Widespread showers
continue to wrap back into western South Dakota. Upslope
enhancement across the northern Black Hills with steep low level
lapse rates. Temperature in the higher elevations of the Black
Hills in the lower 30s...with dot web cam by O'Neil Pass showing
snow accumulating on the grassy areas. Showers will continue
through the day. Another inch of rainfall possible across the
northern Black Hills. Gusty northwest winds on the plains of
western South Dakota have been near low end of advisory criteria.
Will leave advisory in effect through this morning.
Upper low begins to shift eastward tonight/Wednesday in response
to strong upper low moving into the Pacific northwest. Increasing
heights and subsidence will bring an end to the showers Wednesday
morning.
&&
Long term...Thursday through Monday
issued at 236 am MDT Tuesday may 21 2013
Weak ridging pushes east over the region on Thursday...with surface
low developing over western Wyoming. A tight pressure gradient will be
in place to the east of the low across eastern Wyoming...eastern Montana...and
the far western Dakotas. Gusty southeasterly winds can be expected
during the day...especially across northeastern Wyoming and far
northwestern South Dakota. Will keep a slight chance for a shower or
thunderstorm over the Black Hills in the afternoon. Warmer air will
continue to build into the area...with highs in the upper 60s and
lower 70s in most areas.
The ridge axis pushes east by Friday...resulting in southwest flow
aloft for the rest of the extended as an upper low stalls across the
Pacific northwest. Temperatures will generally be above average
through the Holiday weekend...with highs in the 70s and lower 80s.
Low level moisture will increase as south to southeast winds
persist. Daily chance for showers and thunderstorms can be
expected...with chances likely increasing late in the weekend. This
still looks like it could be an active period for severe weather
across the Black Hills area and eastward onto the South Dakota plains...
especially Sunday and Monday...as surface low develops over the
eastern Montana/northeastern Wyoming area. This will depend some on the timing
of the disturbances passing through. Models are in fairly good
agreement keeping this pattern in place for the County Warning Area through the end
of the month.
&&
Aviation...for the 12z tafs through 12z Wednesday morning
issued at 527 am MDT Tuesday may 21 2013
Occasional rain showers will continue this morning across much of
western South Dakota and far northeastern Wyoming...with MVFR/IFR conditions
generally persisting across most of the forecast area. VFR
conditions have developed at kgcc and should stay that way through
the afternoon. A more steady rain is expected to continue across the
northern Black Hills through the morning. Showers will begin to
decrease in coverage this afternoon and evening from west to east
as low pressure finally starts to push awat from the region. Gusty
northwesterly winds will continue through the morning...then start
to slowly decrease this afternoon. General MVFR/IFR ceilings should
remain or redevelop across much of the area tonight.
&&
Unr watches/warnings/advisories...
South Dakota...Wind Advisory until noon MDT today for sdz001-002-012-013-026-
030-031-072-073.
Wyoming...none.
&&
$$
Short term...7
long term...26
aviation...26
