Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 300858

Area Forecast Discussion
National Weather Service Aberdeen SD
358 AM CDT Sun Apr 30 2017

.SHORT TERM...(Today through Tuesday Afternoon)
Issued at 358 AM CDT Sun Apr 30 2017

Continue to watch evolution of storm system across the Southern
Plains early this morning. Models continue to bring this storm
system northward through the day, although precipitation onset has
slowed by several hours. Also, models have shifted the QPF back to
the east again, but still hitting the I-29 corridor the hardest.
Precip chances in the James River valley look a bit less now.
Looking upstream, several obs across western KS down into northern
TX have temps in the 32 to 34 degree range with widespread snowfall.
That air will be heading up this way for tonight. After computing
the latest input of QPF, snow ratios, hourly temps, etc., am still
coming up with rather hefty snowfall amounts across the Prairie
Coteau region pushing 8 inches. This seams reasonable given the
dynamics and persistent upslope flow we`ll be seeing. Interesting
development though, since the onset of precip is a bit later today,
it gives more time to warm up today. Therefore, the temp drop this
evening may be delayed some, which ended up bringing snow totals
down a tad outside of the higher terrain features. Initially, storm
total snow grids seemed a bit on the low side over the Coteau, so
fudged snow ratios a bit higher to get the desired results of
heavier accums. Will see how this all pans out but feel the setup is
in place for warning criteria snowfall in a localized area around
the Prairie Coteau. Have therefore upgraded three counties to a
Winter Storm Warning, where the effects of upslope and terrain
features should yield a longer duration of snowfall. Elsewhere,
looking for generally 1 to 5 inches of wet, slushy snowfall.
Buffered the warning with an advisory to highlight these lesser
amounts. Gusty north to northeast winds will bring lowered
visibility within areas of heavier snowfall. System looks to be out
of here by Monday evening.

Will also be watching a couple additional upper level waves dropping
southeast across the area Monday and Tuesday, further west from the
main storm system. These system look to affect mainly the western
Dakotas Monday, with the second system affecting western and central
areas of the Dakotas. Looking at threat for showers and maybe even a
few thunderstorms as we will be developing some steepening lapse
rates thanks to the pool of cool air aloft sitting over the Northern

As for temperatures, highs were increased today, especially for
western areas as the slower onset of thicker clouds and precip will
allow for more warming. Highs were also increased a bit Monday and
Tuesday, again mainly for western areas as 925/850 mb temps are
rather mild and look warmer than what we have been seeing as of
recent when we have been able to realize temps around 60 degrees or
even into the low 60s.

.LONG TERM...(Tuesday Evening through Saturday)
Issued at 358 AM CDT Sun Apr 30 2017

Upper troughing with embedded shortwave activity will bring some
showers to the region for the start of the extended Tuesday night
and Wednesday. Upper ridging will begin to build in late Wed night
and Thursday. With dry conditions expected through the weekend
daytime heating will be given ample opportunity to make the high
temps soar. By the weekend, 850 mb temps in the lower 20s C will
advect into the western cwa. Forecast highs in the upper 60s to
upper 70s Thursday through Sunday could well be underdone. Would not
be surprised to see some 80s by next weekend if these trends


.AVIATION...(For the 06Z TAFS through 06Z Sunday Night)
Issued at 1149 PM CDT Sat Apr 29 2017

VFR conditions will continue for all sites except KATY through the
TAF period. At KATY, expect rain to move in during the early
evening hours and as temperatures cool through the evening, it
will change over to snow. Latest model trends delaying the start
of the precip and lower ceilings so have trended that directions
will this issuance and expect IFR conditions after 06Z.


SD...Winter Weather Advisory from 10 PM this evening to noon CDT
     Monday for SDZ008-022.

     Winter Storm Warning from 10 PM this evening to noon CDT Monday
     for SDZ020-021-023.

MN...Winter Weather Advisory from 10 PM this evening to noon CDT
     Monday for MNZ039-046.



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