Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 171726 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1226 PM CDT Thu Aug 17 2017

Issued at 1224 PM CDT Thu Aug 17 2017

See updated aviation discussion below.

UPDATE Issued at 1014 AM CDT Thu Aug 17 2017

No major changes made to the forecast this morning. Still some
lingering cloud cover over the far eastern CWA on the back side of
the low pressure system that brought rain to the area yesterday.
The rest of the area now seeing mostly sunny skies. No changes
made to winds or temperatures at this time.


.SHORT TERM...(Today through Saturday Afternoon)
Issued at 335 AM CDT Thu Aug 17 2017

Rain is slowly exiting the CWA with just the western fringe still
affecting Big Stone and Traverse counties. Cloud shield continues to
advance eastward as well, although a stubborn low cloud deck is
being revealed as nearly stationary over the Coteau, underneath
the departing mid clouds. Will continue to monitor for fog
potential, but with still a bit of a breeze, it may be tough. A
few hours ago, many of the hi-res models were showing lowered vsby
in the Coteau, so ran with this and inserted some patchy/areas of
fog mention in the grids. Perhaps they were picking up on moist
upslope flow into the Coteau - seemed reasonable so added fog
mention. Although the past couple runs of a few of the hi-res
models have backed off a bit on fog. Nonetheless, still have some
mention of it in the forecast through early morning. May have to
keep an eye on central SD, where hi-res models were not showing
anything, but where it actually makes more sense. Because here,
winds are actually light under the ridge axis and low levels are
still moist. KMBG has recently dropped to 6SM.

For later today, expect the clouds across the east will have pushed
off and it appears to be a mostly sunny day across much of the area
with warmer temps ranging from the upper 70s to the upper 80s. A
nice warm-up after the cooler readings of past days. Will be
watching upper level shortwave energy moving into the western
Dakotas this afternoon. Hi-res CAM solutions show scattered showers
and storms moving into the western CWA by late afternoon or close to
00Z this evening. Instability is minimal but there is a bit of shear
to work with. Expect scattered activity to move eastward across the
CWA through the overnight hours as the shortwave continues moving
east. Lingering shortwave energy will drop southeast across eastern
portions of the CWA on Friday, with continued chances for showers
and thunderstorms.

Conditions dry out Friday night and Saturday with a warm/hot air
mass moving into the region. It`s been a while since this warm of an
air mass has moved into the area as 850 mb temps look to rise into
the +20s Celsius by 00Z Sunday. With favorable south to southwest
mixing winds, temps look to warm quite nicely into the 80s and 90s.
Stayed fairly conservative with highs on Saturday - sticking close
to SuperBlend where otherwise this synoptic pattern might suggest
going higher. All the recent rain and wet soils across the area may
hold temps at bay and prevent highs from overshooting guidance like
we see in extended dry patterns.

.LONG TERM...(Saturday Evening through Wednesday)
Issued at 335 AM CDT Thu Aug 17 2017

The upper pattern will evolve over the course of the long term from
mostly zonal flow with an upper trough across western Canada and a
second trough across the eastern CONUS, to a slight trough across
the central CONUS early next week, followed by increasing ridging
in the western CONUS for the second half of the work week. A
surge of hot air at the end of the short term will bleed over into
overnight temperatures to start the extended, with the front
across the area and south/southwest low level flow across the
eastern half of the state. The front will stall over the region,
with high pressure to the north. Low level flow shifts to easterly
Sunday, and a weak wave in zonal flow will allow for the
development of a lee low on the tail end of this feature late
Sunday. We see favorable placement of a low level jet Monday AM,
along with the right entrance region of a jet streak in North
Dakota. Guidance blend pops at 40-60 percent is fine for a day 3/4
warm front elevated convection event. Due to zonal flow aloft,
this will also be a short lived episode of precipitation with
mainly dry conditions thereafter.

Temperatures for the upcoming week will be defined by cooler air
dislodged out of Canada into the eastern half of the CONUS, and
hotter air building out west, and the CWA in between.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1224 PM CDT Thu Aug 17 2017

For the most part, VFR conditions will prevail across the area
through midday Friday. The exception will be across parts of the
western and southern CWA this evening, when showers and
thunderstorms may develop and slide southeast. Brief periods of
MVFR vsbys in rain are possible with any thunderstorms that




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