Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 211014

Area Forecast Discussion
National Weather Service Aberdeen SD
414 AM CST Tue Feb 21 2017

.SHORT TERM...(Today through Thursday Afternoon)
Issued at 414 AM CST Tue Feb 21 2017

Very warm air aloft today, with 850mb temperatures 2 standard
deviations above climo, ranging between +8C in the northeast to +12C
in our south central counties. +10C is only about 2-3C below the
daily max for KABR as well, according to the SPC sounding
climatology page. Westerly flow will aid in mixing as well, with
mixed temperatures from the James valley east in the low/mid 60s and
across central South Dakota topping out in the upper 60s. Despite
the fact that it is 3am, KPHP has already warmed to 54F with a
southwest wind component. Thus, the only negative to the temperature
forecast is the degree of high clouds. Both the GFS/NAM propagate
these into northeast South Dakota by mid day and out of the CWA by
the mid afternoon, so do not anticipate these will have a long
lasting effect on the temperature forecast.

The only issue with these warm temperatures is the potential to meet
Red Flag criteria. 1/2km winds from mid day through the evening are
quite weak with the exception of over Stanley/Jones/Lyman counties,
where they approach 40kts. Mixed tool for KPHP is closer to 20G35kt,
so we could see a few spots along the far western extreme meet wind
criteria at least, though it will be harder to hit RH criteria.

With a southwest oriented jet of 130kts from California crossing the
intermountain west, and extending into the central plains states,
several of the CAMs are generating some mid level steep lapse rates
and shower activity. NAM profiles support this, though there will be
4-5kft dry layer to overcome. Added mention of rain showers tonight
thanks to the lift associated with the left exit region of this jet
and a series of weak waves evident at 500mb. Temperatures overnight
will again remain above freezing, and with warm ground temps -
shower activity will have little impact.

Low pressure moves across the Western Lakes region Wednesday, with
weak cold advection in the low levels. Models generate some light
QPF within this regime, so will leave in low pops, however NAM
profiles are more suggestive of Stratus up to 5kft thick moving
overhead and thus possibly some light drizzle. Thankfully
temperatures are still expected above freezing Wednesday.

Cold advection and cloud cover will likely result in falling
temperatures through the day Thursday, and the NAM BUFKIT soundings
suggest some drier air entraining from the northeast as this system
takes shape mainly to the south of the CWA. Still seeing GFS BUFKIT
profiles shift towards all snow by mid day, with the main focus for
accumulation I90 and south.

.LONG TERM...(Thursday Evening through Monday)
Issued at 414 AM CST Tue Feb 21 2017

The main challenge will be the storm system impacting the region at
the start of the extended. By Thursday evening, all precip will have
changed over to snow. The GFS has shifted just slightly north again,
but the ECMWF continues to take a more southerly track. Any
significant snow accumulations will be confined to the far southern
cwa, mainly along I-90. Gusty winds could lead to some areas of
blowing snow on Friday across the southeastern cwa.

Heights will remain suppressed in upper troughing through the
weekend. That said, temps will still be right around or slightly
above average with highs in the upper 20s to 30s. Monday will bring
some warm air advection ahead of a low moving off the Rockies. Temps
could climb into the lower 40s. The next best chance of any precip
will be with this low late Monday.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday Night)
Issued at 1132 PM CST Mon Feb 20 2017

Conditions are VFR right now, and skies are clear to partly
cloudy. Winds have become light and variable or picked up a light
southerly direction and speed. Guidance is still by and large fog
free. The latest wrinkle is the possibility of some patchy dense
fog. The temp/dewpoint spread has fallen to 1 to 3 degrees at KABR
and KATY and there have been hints of perhaps some light fog
trying to develop at/near these two terminals, so did introduce a
temporary 2sm IFR visby in fog late tonight/early Tuesday morning.
Otherwise, expect VFR conditions to prevail over the next 24




SHORT TERM...Connelly
AVIATION...Dorn is the U.S. government's official web portal to all federal, state and local government web resources and services.