Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 210154 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
854 PM CDT Sun May 20 2018

Issued at 839 PM CDT Sun May 20 2018

Trends in the most recent few model runs of the Rapid Refresh/HRRR
models still depict an area of low clouds (currently noted over se
SoDak) to begin spreading/expanding northward into this cwa later
tonight, mainly after 11 PM CDT as low level winds begin to switch
around to a south-southeast direction. This change in direction
will also aide in some surface/near-surface moisture transport up
into this cwa overnight. The increase in cloud-cover and low level
moisture should help keep temperatures from tanking overnight.

UPDATE Issued at 640 PM CDT Sun May 20 2018

See below for an aviation forecast discussion for the 00Z TAFs.


.SHORT TERM...(This Evening through Monday)
Issued at 337 PM CDT Sun May 20 2018

A broad upper level trough of low pressure currently over Nebraska
will lift northeastward tonight through Monday morning. Increasing
cloud cover can be expected for most of the CWA tonight. Based on
several CAMS, along with support of the NAM/GFS, have increased pops
late tonight through Monday for our far eastern CWA. While pcpn
should depart to the east by 18Z, cloudy skies may remain over the
eastern CWA with cooler temperatures possible. High temperatures
east of the James Valley may only reach the low to mid 60s.
Temperatures should reach the mid 70s elsewhere.

.LONG TERM...(Monday Night through Sunday)
Issued at 337 PM CDT Sun May 20 2018

The models were consistent and agreed well through the long term
with the upper level flow and surface features affecting our region.
The main issue will be the large upper level low pressure area over
the southwest U.S. and its affect on our region from Monday night
through Thursday night. There will be a couple short wave troughs
coming off this upper low and across our region through Wednesday.
This main upper level low pressure area will then weaken as it moves
northeast and east across the northern part of our region/southern
Canada into Friday. Until then warm, moist, and unstable air will be
advecting into our region on south to southeast winds. Each short
wave trough and warm frontal boundary push north/LLJ increase will
interact with this air bringing several rounds of showers and
thunderstorms. Otherwise, the last good round of showers/storms will
be Thursday night as a surface cold front pushes from west to east
across the region. The air behind this front will be drier and only
a little cooler through the weekend as northwest to north winds
prevail. Overall, Friday through Sunday looks to be mainly dry with
only a few showers/storms possible as upper level ridging builds in.
Highs through most of the period will be in the 80s which is from 5
to 15 degrees above normal.


.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 640 PM CDT Sun May 20 2018

KPIR/KMBG are forecast to be VFR for the next 24 hours. However,
will monitor conditions across central/north central South Dakota
for potential sub-VFR stratus/fog development mainly between 07Z
and 13Z Monday.

KABR/KATY are forecast to be VFR to start, but should see a drop
to sub-VFR cigs at least at KATY later tonight after 06Z and
persisting through much of the day Monday. It`s not so clear cut
at KABR, as this terminal could be on the fringe of low clouds
overnight. KATY could see isolated to scattered off-and-on showers
overnight, too, as an area of low pressure lifts up across the




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