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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota
250 am MDT Friday Mar 27 2015

Short term...today through Saturday night
issued at 248 am MDT Friday Mar 27 2015

Western Continental U.S. Ridge will shift east in the period
supporting much warmer weather over the region. Ll baroclinic zone
and associated passing impulses and ensuing light precipitation...will
shift east and wane this morning...with mainly dry conds through the
remainder of today. Compact but strong Pacific upper level trough will
shift quickly east tonight through Sat...with shortwave ridging
ahead of this feature. Upper level trough and associated surface cold
front will push into the region Sat night...supporting very windy
conds and chances for rain showers.

Today...ll fgen and associated forcing will push east across the
eastern forecast area this morning. Weak forcing and dry ll profiles will
support only light precipitation...mainly flurries. Surface warm front will
shift east with gusty northwest winds developing this afternoon. Weak
passing upper level impulse/lingering Pacific moisture/and steep lapse
rates may be enough to support a few instability rain showers across the bh
and southeast. Have included some slight chance probability of precipitation for this.
Otherwise...dry conds expected most places. Highs will generally be
in the 60s.

Sat...shortwave ridge and associated thermal ridge will pass over
the forecast area...with increasing westerly flow. This will allow for a very
warm day with 70s most areas and a few 80s in the Lee of the bh/S.
Upper trough and associated cold front will push into the region Sat
evening. Limited...but sufficient ll moisture may allow for a few
scattered-isolated rain showers with possibly a ts across the far north closer to the
best upper level support early evening. Better chances for
rain showers/isolated ts will develop later in the evening as the main lobe of
lsa will advection across the region. The best chances for precipitation will be
across the far north given the track of the upper wave...which will
take most of it/S associated lsa/uvm across ND. Limited probability of precipitation over the
southern 2/3 of the forecast area given limited moisture/forcing. The biggest
impact from this system will be winds. Strong pressure rise couplet
coupled with cold air advection/steep ll lapse rates/and potential shower outflow
will support very strong gusty northwest winds along the surface front. Wind
gusts in excess of 60 miles per hour look possible...especially across northwest South Dakota and in
the Lee of the bh/S. Have adjusted winds up.

Long term...Sunday through Thursday
issued at 248 am MDT Friday Mar 27 2015

Upper level ridge rebuilds over the northern plains
for Sunday through Tuesday...with dry conditions and well above
average temperatures expected. A strong shortwave trough will slide
across southern Canada with the southern end of the trough clipping
northern portions of the forecast area Tuesday night...with some
showers possible. A surface cold front will accompany this upper
disturbance...with winds shifting to the northwest and becoming very
breezy. Upper flow transitions to northwest for the end of the
week...with models showing a few more weather disturbances moving
through. Precipitation chances increase across the area after Thursday.

&&

Aviation...for the 12z tafs through 12z Saturday morning
issued at 248 am MDT Friday Mar 27 2015

Mainly VFR conditions are expected through Saturday
morning. A weak weather disturbance will produce mostly cloudy skies
today with a few light sprinkles moving through the Black Hills area
during the afternoon. Brief MVFR ceilings and visibilities will be
possible in the vicinity of showers.

&&

Fire weather...
issued at 248 am MDT Friday Mar 27 2015

Warm temperatures with dry westerly flow will support
potential critical fire weather conds Saturday afternoon across
NE Wyoming and southwest South Dakota. Minimum relative humidities of
15 to 20 percent with westerly winds of 20 to 30 miles per hour are currently
forecast. There is the potential for even lower relative
humidities Saturday afternoon. In addition...a strong cold front
will support even stronger winds Saturday evening...along with a
wind shift. Winds may gust to around 60 miles per hour with the cold front
passage. Isolated thunderstorms will be possible across portions
of northeast Wyoming Saturday evening. There is some uncertainty
with respect to the degree of wind speeds as well as minimum relative humidity.
Given these concerns...a Fire Weather Watch has been issued for
Sat afternoon/evening.

&&

Unr watches/warnings/advisories...
South Dakota...Fire Weather Watch from Saturday afternoon through Saturday
evening for sdz262>264.

Wyoming...Fire Weather Watch from Saturday afternoon through Saturday
evening for wyz259-297-298.

&&

$$

Short term...jc
long term...15
aviation...15
fire weather...jc

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