Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 150214 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
914 PM CDT Thu Sep 14 2017

Issued at 912 PM CDT Thu Sep 14 2017

Beginning to see cloud cover increase across much of the area, so
made some adjustments to account for that. No changes made to
winds or temperatures at this time.


.SHORT TERM...(This Evening through Friday Afternoon)
Issued at 302 PM CDT Thu Sep 14 2017

An area of low pressure is currently located over south central SD
with a cold front just north of Watertown. Warm 700 mb temps of +10C
are capping convection along the front. A weak upper level
shortwave currently over northwest SD will bring light showers to
our northwest through this evening.

The main upper level trough is located over the desert southwest.
This trough will lift northward tonight which will bring
increasing chances for showers and thunderstorms for locations
along and west of the Missouri Valley by Friday morning. There is
a potential dry slot moving into the eastern CWA during the mid
morning hours. If the dry slot does develop and skies clear off,
then highs in our eastern CWA will be warmer than expected.
Clearing skies and destabilization will play an important role in
strong storms. Went conservative with the severe threat as the
signal is not clear enough.

The western portion of the CWA should see a decent amount of
rainfall from this storm system. ESRL`s Extreme Probability page
shows accumulated pcpn for this CWA in the 90-95th percentile from
0Z Friday to 0Z Saturday. The western Dakotas are in the 99th
percentile for accumulated pcpn.

.LONG TERM...(Friday Evening through Thursday)
Issued at 302 PM CDT Thu Sep 14 2017

Pcpn chances/temps are the main issue during the time period. All
the preferred models are indicating a negative PNA pattern across
the conus, meaning west conus troffing, with east conus mid level
ridging. As for the deterministic details, the models are in fair
agreement until post 120 hours. After that time period, shortwave
and frontal timing becomes significantly different. Needless to
say, won`t change to much during that time period given the
disparities, and will stick fairly close to model blend. However,
did bump up overnight lows some Tuesday and Wednesday morning
given LLJ across the forecast area. Rain chances appear to be
mostly confined to the early part of the forecast (early this
weekend), as well as toward the middle of next week as energy
lifts out of the western trof northeast across the region.
Temperatures will favor below normal Saturday and Sunday, but then
should trend back above normal next week as warm air once again
flows north into the Northern Plains.


.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 624 PM CDT Thu Sep 14 2017

VFR conditions will prevail across the area this evening. A
frontal boundary will move across the area overnight into the day
Friday, and will likely be the focus for shower, and possible
thunderstorm, activity. Cigs will fall to IFR levels across the
CWA late tonight and are expected to remain in place through the
day Friday. Periods of MVFR vsbys will be possible with the




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