Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 212036

Area Forecast Discussion
National Weather Service Aberdeen SD
336 PM CDT Sun May 21 2017

.SHORT TERM...(This Evening through Monday Afternoon)
Issued at 331 PM CDT Sun May 21 2017

A broad upper level trough over Minnesota will continue impacting
the eastern CWA through this evening with mostly cloudy skies and
breezy northwesterly winds. Further west, diurnal showers and
thunderstorms have developed and should mainly affect areas west of
the Missouri River before diminishing upon sunset. The biggest
question for tonight is whether or not frost forms in the low lying
areas of the James River valley and points east. Several areas west
of the Missouri River valley saw low temperatures last night in the
lower 30s, which could be possible for the James River valley
tonight. That said, increasing clouds ahead of our next storm system
could keep temperatures from falling. Will continue with the mention
of patchy frost and fog tonight where the previous forecast

Models have been very consistent with an upper level shortwave
tracking across the region on Monday. Much like today, there should
be enough instability around for scattered thunderstorms to develop,
mainly south of Highway 212. The SREF prob thunder also highlights
the southern CWA. Much like the current convection out west, some
thunderstorm on Monday may feature gusty northwesterly winds.

.LONG TERM...(Monday Evening through Sunday)
Issued at 331 PM CDT Sun May 21 2017

Starting out Monday night in a profoundly elongated upper level
longwave trof/closed low system (stretches from the Dakotas to
Quebec Province), with a shortwave actually traveling west and south
toward the region. Plenty of cloud cover and cold conditions (10 to
20 degrees below climo normal one more time) setting up with
intermittent light rain/drizzle expected across the eastern third of
forecast zones between late Monday night and Tuesday evening.
Collaborated Tuesday high temperature as a target of opportunity and
lowered highs a solid 3 to 5 degrees throughout and east of the
James River valley. High pressure then builds into the region from
the west-northwest, drying and warming things up for mid week.
Models all seem to agree on track/timing of some strong polar-jet
directed shortwave energy slamming into the Pac-NW early in the week
and then slowly working east along the northern tier states through
the rest of the week before running into this large blocky pattern
over eastern No-Am and nearly stalling over south central Canada by
week`s end. This low pressure energy will help to shift the flow
pattern around to more of a west or southwest trajectory by
Thursday, and work to keep it that way through the weekend. This
will also allow for periodic passages of mid-level shortwaves/precip
chances through the region between late Wednesday night and
Saturday. Based off the 12Z deterministic and ensemble solutions, it
appears temperatures will finally climb their way back to around
climo normal from the middle of the week all the way through the


.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
Issued at 628 AM CDT Sun May 21 2017

VFR conditions can be expected through the valid taf period. The
gusty northwesterly winds will subside later this evening. Another
storm system crossing the region on Monday will bring sct showers
and thunderstorms. At this time, KPIR will have the best potential
of seeing thunderstorms.




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