Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 220011 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
611 PM CST Sat Jan 21 2017

Issued at 610 PM CST Sat Jan 21 2017

Dense fog advisory has been issued for the eastern portion of the
CWA, mainly along the Sisseton Hills region. The advisory is in
effect until noon Sunday.


.SHORT TERM...(This Evening through Sunday Afternoon)
Issued at 218 PM CST Sat Jan 21 2017

Similar to yesterday afternoon, drier air has again moved across our
far southwestern counties. After another brief reprieve from the
widespread fog this afternoon, conditions are looking to degrade
again overnight. This will be most likely over our east, where
temperatures in the low to mid 30s today has resulted in snow melt
and, as a result, additional low level moisture. Areas along the MO
river will be on the edge of these very low visibilities too.
Meanwhile across the James Valley, a majority of the area should
have visibilities stay around 2SM or greater through the rest of the
period. Uncertainty is high though.

The best chance of any drizzle or freezing drizzle will be over our
northeastern areas. This will be thanks to the exiting sfc low over
southern MN that still has a trough extending up across that area
into early this evening. While the sfc high exits to northern
WI/upper MI tonight, a ridge of high pressure will be slowly
building into our region tonight and be across the western half SD
by the end of the day Sunday. Icy conditions/untreated roadways will
again be possible overnight into Sunday morning over all but the
northeast corner of the CWA, where temperatures should remain
above freezing overnight.

.LONG TERM...(Sunday Evening through Saturday)
Issued at 218 PM CST Sat Jan 21 2017

A somewhat active pattern for the extended. The long wave pattern
across the conus has been fairly progressive as of late, and that
should continue for the majority of the period. However, toward next
weekend the pattern looks as if it will shift toward a positive PNA
setup, featuring a west coast ridge and central/eastern CONUS trof.
Meanwhile, the main system to deal with is a storm ejecting out of
the desert southwest Monday night and Tuesday. That storm will move
across the Central/Northern plains Tuesday through Wednesday. A
fairly weak trowal structure does appear to set up over especially
southern South Dakota Tuesday, spreading into southern MN Tuesday
night. This is also the favored area for enhanced UVM per left exit
region of H3 polar jet. For now am forecasting up to 3 inches of
snow over southern portion of the CWA. Models have been waffling
somewhat with the track of this system, thus snow total forecast
confidence is not particularly high. Once the system gets on
shore, perhaps there`ll be more consistency and agreement between
the various long term NWP models. Temperatures will start the
period above normal, but then will trend toward normal mid week
behind the departing storm. However, above normal temps look
possible again by next weekend as a mild airmass gets pulled east
off the high plains.


.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 527 PM CST Sat Jan 21 2017

IFR cigs and vsbys in fog expected again tonight across the far
eastern portion of the CWA. MVFR/VFR conditions will be more
common across the central and west. Vsbys will improve across the
east after sunrise on Sunday, but the low cigs will remain
through the day.


SD...Dense Fog Advisory until noon CST Sunday for SDZ007-008-011-

MN...Dense Fog Advisory until noon CST Sunday for MNZ039-046.



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