Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
529 PM MDT Wednesday may 22 2013
Short term...this evening through Thursday night
issued at 241 PM MDT Wednesday may 22 2013
20z upper level analysis shows a low over Iowa and the
northwest Continental U.S....with a ridge moving into the northern plains. Low
clouds are draped over South Dakota...but have been eroding since
late morning. Areas of drizzle have accompanied the fog/low
clouds...with radar picking up on very light returns. The surface
high is working its way into the area. Winds are light and
temperatures are in the middle 40s to 50s.
Winds will become east to southeast tonight as the surface high
moves eastward. Patchy fog is expected across the foothills and
southern County Warning Area as the light easterly winds push moisture against the
hills. However...southeast winds will be stronger across northeast
Wyoming and northwest South Dakota as a surface low begins moving in
and the pressure gradient tightens. Low clouds are expected across
northeast Wyoming...but the stronger winds should preclude fog
formation there. Lows will be in the lower 30s to lower 40s.
On Thursday...southeast winds will increase across the area. The
strongest winds of 25-35 kts gusting to near 50 kts are expected
across northeast Wyoming and northwest South Dakota. At this point
it looks like a high-end Wind Advisory for these locations...so
issued a Wind Advisory for northwest South Dakota. The strongest
pressure falls will be across Wyoming...and so later shifts will
need to determine if a High Wind Warning is necessary for northeast
Wyoming. Highs Thursday will be mainly in the 60s...with 50s in the
Black Hills.
Winds will gradually decrease Thursday evening...but some locations
may remain breezy overnight. As the low approaches the
region...conditions will become favorable for showers and
thunderstorms across southern South Dakota beginning overnight
Thursday. Moisture convergence...along with a low-level jet and
750-1000 j/kg MUCAPE develop across southern South Dakota by 12z
Friday...so added a slight chance of showers and storms there. Lows
will be in the lower 40s to lower 50s.
&&
Long term...Friday through Wednesday
issued at 241 PM MDT Wednesday may 22 2013
Upper low over the Pacific northwest starts to push to the northeast
slightly towards the end of the week into the weekend while upper
ridge axis over the plains works towards the Midwest. This will
result in southwesterly flow aloft bringing daily chances for
showers/thunderstorms. Chances continue into early next week as trough
with upper low deepens and starts sliding east. Temperatures will
remain above average.
&&
Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 527 PM MDT Wednesday may 22 2013
Low ceilings will re-develop tonight...particularly over northeastern
Wyoming and far western South Dakota. Patchy fog is also possible.
Conditions will improve Thursday morning...though gusty
southeasterly winds will develop.
&&
Unr watches/warnings/advisories...
South Dakota...Wind Advisory from 9 am to 9 PM MDT Thursday for sdz001-002-
012>014-025-026-031-072-073.
Wyoming...none.
&&
$$
Short term...pojorlie
long term...77
aviation...10
