Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 240320 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
920 PM CST Mon Jan 23 2017

Issued at 915 PM CST Mon Jan 23 2017

There is too much uncertainty at this time to make any major
adjustments to the forecast. A band of light snow continues across
far north central SD. Otherwise, most of the region is
experiencing some flurries. Models have not picked up on the band
of snow along the ND/SD border so initialization so far on the 00z
runs has been poor. The 00z run of the NAM leaves the entire
northeastern part of the state precip free for this event. Since
this is a major shift from the previous forecast will not act on
this least until there is some support from other
00z models as they update.


.SHORT TERM...(This Evening through Tuesday Afternoon)
Issued at 208 PM CST Mon Jan 23 2017

Decent system headed out across the plains tonight through Tuesday
night. The biggest challenge remains qpf/snowfall.  The 12z
deterministic models are still somewhat different with their sfc/mid
level low track, and of course with their respective pcpn amounts
and locations. The ECMWF remains the furthest south and lightest.
GFS furthest north and heavier with pcpn.  NAM is probably the least
aggressive over my cwa, and the CMC is in between.  GEFS probabilities
and plumes still suggest the operational run of the GFS is too far
north, so have sided more so with models favoring a southern track.
WWD`s latest guidance also looks closer to what we are thinking.
Less qpf across the northern cwa, but more over the south central
sections. The highest snowfall rates should occur during the day on
Tuesday, especially along the I90 corridor where models continue to
indicate better trowal/deformation zone formation. Tuesday night the
pcpn gradually tapers off from west to east over the forecast area.
Gusty winds will provide for some blowing snow, especially over the
western cwa where guidance indicates a little higher winds.
Temperatures both tonight and Tuesday will favor above normal given
plenty of clouds.

.LONG TERM...(Tuesday Evening through Monday)
Issued at 208 PM CST Mon Jan 23 2017

Much of the snow associated with the storm system will exiting
our far northwestern counties by 00Z, and continue the slow
diminishing trend and be east of the James River Valley if not out
of the entire CWA by 00Z Thursday. The main concerns initially will
be the north-northwest winds still hovering between 15 and 20kts and
gusts of 25-30kts. Fcst models are starting to come into better
agreement with the location of the sfc low over far northeastern
NE/southwestern IA at 00Z Wednesday. While the strongest pressure
rises will be well to our southwest, a 3mb 3hr change is expected in
the evening south of MBG. This will be the area where we`ll keep the
strongest winds. Blowing snow will be a concern. With snow ratios
increasing to 15:1 to near 20:1, drifting snow will also have more
of an impact. Another 2-3 inches will be possible across our
southern border Tuesday night. Elsewhere, amounts around 1 inch
will be more likely. As has been the trend the last several days, the
GFS remains on the northern side of the operational solutions, while
the ECMWF and Canadian are to the southwest. By 12Z Wednesday the
sfc low should bet set up eastern IA to southern WI.

Lingering northerly flow and the slow exit the the sfc low Wednesday
night should keep flurries or light snow showers across our far
northeastern counties.

Otherwise, mainly dry weather is figured through Monday morning as
we remain a trough set up across eastern Canada and the NE U.S...and
dominant high pressure across the western U.S. Did increase winds
Saturday, with gusts of 20-30kts possible. After highs in the low
20s on Thursday, expect high temperatures to slowly crawl back into
the 30s by Monday.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 530 PM CST Mon Jan 23 2017

Visibilities in some light snow are currently lower than model
guidance is indicating so stuck with a fairly pessimistic forecast
as the snow moves through tonight and Tuesday. MVFR/IFR vsby is
expected as snow spreads across the region. Cigs will fall to IFR
overnight and remain there through the rest of the valid TAF
period. Snow may be heavy at times near KPIR. Winds will increase
and become gusty by late Tuesday afternoon.


SD...Winter Storm Warning from 3 AM CST /2 AM MST/ Tuesday to 6 AM
     CST /5 AM MST/ Wednesday for SDZ033>037-045-048-051.

     Winter Weather Advisory from 3 AM CST /2 AM MST/ Tuesday to 6 AM
     CST /5 AM MST/ Wednesday for SDZ015>023.



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