Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 191728 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1228 PM CDT FRI AUG 19 2016

.UPDATE...
Issued at 1041 AM CDT FRI AUG 19 2016

Two areas of rainfall this morning to affect our cwa today. The
first area will continue to lift into northeast SD and west
central minnesota into the afternoon. The second larger area with
the main upper level trough will continue to spread into central
and north central South Dakota into the afternoon. Therefore,
adjusted weather and pops through the afternoon hours across the
cwa. Also, adjusted temperatures downward a little.

&&

.SHORT TERM...(Today through Sunday Afternoon)
Issued at 402 AM CDT FRI AUG 19 2016

Main complex of showers and thunderstorms has cleared the CWA,
leaving behind mostly dry conditions for the time being. Keeping an
eye on a vort across northern Nebraska, with rain showers associated
with it. This will continue to rotate northeast into the FSD CWA
through the morning, with showers potentially moving northeast along
the ABR/FSD CWA boundary. The morning hours will largely be dry
across much of the CWA aside from this vort moving out of Nebraska.
Although, will be watching the progression of the potent upper level
trough which is currently digging south-southeast across southwest
Canada and into Montana. Synoptic scale lift ahead of this trough
will eventually rotate into the western Dakotas later today, with a
rather large area of rain/showers progressing into the western CWA.
Models agree rather well with this scenario, and discovered the
CONSShort POP grids seemed to reflect a likable forecast. Closely
followed this for today`s and tonight`s POPs. The James Valley
region towards the northern Coteau area may actually stay dry
through the day and will have to await the arrival of the main upper
trough later this evening before showers move into the area. Now
that yesterday`s cold front has brought in lower dewpoints, the air
mass this afternoon will be much more stable. Therefore, do not
expect any severe weather and may even be difficult to get any
thundershowers going. Wx grids reflect shower chances with just
slight thunder chances.

For Saturday, the upper trough will continue to push east, but
eastern portions of the forecast area will remain in a steep lapse
rate environment with some daytime heating. Have expanded shower
chances a bit further west, although overall instability is lacking
still, so expect mostly just showers with an isolated thunder chance.

Conditions dry out Saturday night as a surface ridge settles over
the region. If skies can clear, temperatures will cool off
considerably under the chilly air mass and light winds. It would
appear at this point that low temps Saturday night/Sunday morning
will drop into the 40s. Although, favored cool spots under ideal
radiational cooling conditions may even see low to mid 40s. Sunday
looks pleasant with warm air advection ramping up. Highs will
rebound some back into the 70s and lower 80s.

.LONG TERM...(Sunday Evening through Thursday)
Issued at 402 AM CDT FRI AUG 19 2016

The overall pattern transitions between a low amplitude upper ridge
overhead initially, with an upper trof over the Pacific Northwest.
The upper low moves across southern Canada Tuesday. This will
generate southwest flow aloft, resulting in an elevated mixed layer
moving across the CWA Monday-Tuesday, with 700mb temperatures
upwards of +12 to +14C and 850mb temperatures peaking Tuesday AM
between +21 to +29C. 850mb dewpoints are only around +11C at the
peak, which would generate surface dewpoints only in the mid 50s to
possibly near 60F. The limited moisture return and elevated mixed
layer will likely hamper surface based convection. Will maintain
SUPERBLEND pops at this point, however both the GFS/ECMWF are rather
conservative with QPF along the front. We will however see
temperatures heat up into the 90s for much of the CWA during the
timeframe as 850mb temperatures are 1 to possibly 2 standard
deviations above climo.

We will see an upper trof overhead for the rest of the period, with
an initially surge in cold advection Tuesday night/Wednesday. Cool
mid/low level temperatures will persist through the end of the work
week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1225 PM CDT FRI AUG 19 2016

VFR conditions are expected through the period, except in heavier
showers where vsby may fall to mvfr. Rain showers, with perhaps
an isolated lightning strike, will move from west to east across
the region this afternoon and overnight before exiting.

&&

.ABR Watches/Warnings/Advisories...
SD...NONE.
MN...NONE.
&&

$$

UPDATE...Mohr
SHORT TERM...TMT
LONG TERM...Connelly
AVIATION...Wise



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