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Area forecast discussion...updated 
National Weather Service Aberdeen South Dakota
1232 am CDT Wednesday Apr 16 2014

Update...
06z aviation discussion updated below.

With just a few hours remaining before a vigorous upper
circulation over southern Montana/northern Wyoming works its way out onto
the northern plains...models should be converging on a precipitation
solution. That doesn't seem to be the case this evening. The 18z
GFS/NAM solutions /and now the 00z NAM solution/ all continue to
highlight a large quantitative precipitation forecast/snow accumulate bulls-eye across portions of
central and north central South Dakota through sunrise
Wednesday...but the latest output from the hourly update model
/rapid refresh model/ suggests little if any precipitation will be
falling across said area by sunrise. Assuming the rapid refresh
model has checked out for a few forecast cycles this
evening...still expecting an overall increasing trend in precipitation
returns/coverage on radar heading toward morning. Previous
thinking still holds...strong fronto-forcing/lift/instability
combo in place late tonight through Wednesday afternoon for a
mesoscale-scale heavy banded precipitation event...where p-type on the
front end of the event will be either rain or a mixture of
freezing rain and sleet transitioning to snow with 6 or more hours
of potential for moderate to heavy snow beneath a mesoscale-scale
banded feature /where ever it ends up setting up/. Tried to
highlight banded precipitation higher amounts in west-southwest update.
Breezing/windy easterly winds for a few more hours switching to
northerly and increasing on Wednesday...so along and east of the
James River Valley from late Wednesday morning through early
Wednesday evening that snow/blowing snow potential with markedly
reduced visibilities is still in place.



&&
Previous discussion...
short term...tonight through Thursday night

An interesting forecast to say the least...with precipitation type/amounts
the main problem. For tonight decent looking system over the northern
rockies will be digging south and ejecting into the northern
plains. Uvm per various Omega/q vector/frontogenesis/divergence forecasts
still looks pretty impressive across my northeastern County Warning Area after
about midnight...lasting until about noon over the far east. One
noted change between the most recent runs and past runs is the
faster change over to all snow. Both the GFS/NAM now indicate
lesser chances for freezing rain vs snow/sleet. This could add more to
accumulation totals vs previous thoughts/ideas. The good news is
the storm appears to be fairly progressive despite a closing off
700 mb low over northeast South Dakota...so improvement should occur
during the middle to later part of the afternoon as system moves
away from the region. The juxtaposition of all elements still
appears to target the upper Mississippi River valley with the
worst impacts. Nonetheless...feel an advisory is justified over
my northeast County Warning Area given occurrence of mixed precipitation type/accumulating
snow/sleet right before the start of morning travel to/from work
and school. So an advisory will be hoisted for late tonight through
the day on Wednesday over northeast South Dakota and west central
Minnesota. The rest of the forecast looks fairly tranquil as short wave
ridging builds a head of the next system. Temperatures overall
will gradually be on the rebound Post Wednesday...with above
normal temperatures possible by the weekend.

Long term...Friday through Tuesday
an upper ridge will extend across the central Continental U.S. At the onset
of the period. However...an upper low will skirt across Canada
with the associated frontal boundary sweeping across the northern
plains. Moisture profiles have middle level dry air in place
initially...but look to saturate quickly along the front.
Therefore the forecast holds slight chance to chance probability of precipitation for
light rain Saturday. Otherwise pretty quiet in the long term.
There may be some weak shortwave energy moving across the region
late Sunday and Monday...but really no model consensus with that
feature. Models do agree on an upper ridge building over the
region by early next weak however...and temperatures should return
to more seasonal values...even above normal by early next week as
model 925 mb temperatures rise into the teens...maybe even 20s by
Monday and Tuesday.



&&

Aviation...
06z tafs for the kabr...Katy...kpir and kmbg terminals

A low pressure system working into the region will cause VFR
flight Cat conditions to deteriorate into MVFR/IFR conditions over
the next 6 to 12 hours.

Basically...precipitation developing across western South Dakota in
the form of rain will spread over into eastern South Dakota/west
central Minnesota. In the process of doing so...the atmosphere
will cool off enough to see rain change over to snow...perhaps
with a small window of time when p-type switches from rain to
freezing rain/sleet before completely switching over to snow.

A band of heavy snow is still expected by late morning somewhere
over northeast South Dakota/west central Minnesota...and where
ever this occurs the most significant visby reduction from both
falling and blowing snow will occur.

Breezy/windy east to northeast winds will continue their
transition around to north-northwest winds today before gradually
subsiding later Wednesday night.




&&

Abr watches/warnings/advisories...
South Dakota...Winter Weather Advisory until 6 PM CDT this evening for Clark-
Codington-day-Deuel-Grant-Hamlin-Marshall-Roberts.

Winter Weather Advisory until 6 PM CDT this evening for Brown-
Edmunds-Faulk-McPherson-Spink.

Minnesota...Winter Weather Advisory until 6 PM CDT this evening for Big
Stone-traverse.

&&

$$
Update...mohr
short term...tdk
long term...serr
aviation...mohr

Weather.Gov/Aberdeen