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Area forecast discussion...updated
National Weather Service Aberdeen South Dakota
933 PM CDT Tue Apr 25 2017

Update...
issued at 923 PM CDT Tue Apr 25 2017

Precipitation beginning to increase across parts of the eastern
cwa, so have bumped up pops for the remainder of the night. May
need to lower pops across the west shortly as echoes beginning to
dissipate there. No changes made to winds or temperatures at this
time.

&&



Short term...(this evening through Wednesday afternoon)
issued at 328 PM CDT Tue Apr 25 2017

The main issue in the very short range will be pcpn...type and
amounts. System currently over the southern High Plains will lift
northeast tonight and Wednesday. Meanwhile, an upper
circulation/pv anomaly over western South Dakota is expected to
slowly eject northeast. Energy associated with this feature is
expected to bring a mixed bag of pcpn to the eastern parts of the
region late tnt and Wednesday. Temperatures remain relatively
warm aloft over the eastern County Warning Area in vcnty of the glacial
lakes/Sisseton hills. This is where the highest potential for any
mixed pcpn will take place in the next 24 hours. The Gem/GFS/hrrr
all show some sort of a trowal like feature forming over southeast
North Dakota tnt and early Wednesday, extending south into the
far northeast part of the County Warning Area. 300 mb progs also indicate some
potential for uvm associated with the right entrance region of
jet stream. Model blend came up with potentially an inch or more
snow over these areas, and based on sfc temps that certainly seems
possible. Later shifts will have to monitor for any mesoscale
bands that might set up. On Wednesday, slow clearing from west to
east is expected with temperatures eventually recovering nicely
west of the James Valley. Temperatures overall will be cold and
below normal through mid week.



Long term...(wednesday evening through tuesday)
issued at 328 PM CDT Tue Apr 25 2017

A ridge of high pressure extending from Canada will remain
across northeastern South Dakota and west central Minnesota through much of the
period. Light snow will be exiting the northeastern counties
Wednesday night, with little to no additional snowfall. This will be
while the 500mb trough set up from the eastern Dakotas down through
OK exits only slightly to the east. The main 500mb low will continue
to spin across northern Minnesota and Ontario into Thursday night.

The next chance of wet weather will arrive Thursday night over south
central SD, as the sfc ridge remains in place across the northeast.
With borderline temperatures, a mix of rain or snow will be
possible, transitioning to just rain during the day Friday. The GFS
has trended drier/farther south with this system, as a 500mb ridge
noses across the area, embedded within a broad trough set up across
much of the nation.

Will look for the large trough over the U.S. To stay in place, as
the main low dives across New Mexico on Saturday and begins to eject
northeastward from OK up through Iowa Sunday through Sunday night.
Will need to monitor the latest trends for this potent and rapidly
evolving system, as a prolonged period of precipitation looks more
and more likely over our extreme southeast or just to our east.
Mixed precipitation will be possible over that area late Saturday
night as temperatures fall into the low to mid 30s. Otherwise, the
GFS and European model (ecmwf) do agree on rain returning to western and central South Dakota
by late Monday night into Tuesday as the 500mb low shifts across the
upper Great Lakes and into Canada.



&&

Aviation...(for the 00z tafs through 00z Wednesday evening)
issued at 625 PM CDT Tue Apr 25 2017

IFR/MVFR cigs will remain in place across the area tonight and
into the day Wednesday. Precipitation currently occurring over the
western County Warning Area will dissipate this evening, while another area of
precipitation will affect the east tonight into Wednesday morning,
most likely in the form of light snow. Vsbys will fall into the
MVFR category with the precipitation. Cigs will likely lift to
VFR levels across the western County Warning Area Wednesday afternoon.

&&



Abr watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
&&

$$

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