Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 182038

Area Forecast Discussion
National Weather Service Aberdeen SD
338 PM CDT Thu May 18 2017

.SHORT TERM...(This Evening through Friday Afternoon)
Issued at 338 PM CDT Thu May 18 2017

Starting to see some scattered light returns on radar approach the
southwest CWA. Expect these light showers to affect the southwest
counties late this afternoon and into the evening as the main upper
low moves very little. Models continue to suggest mainly the
southern half of SD being affected by precipitation through the day
Friday, as the main upper low is still over CO by Friday afternoon.
Tapered off POPs a bit across the northern counties based on these
latest trends.

As for temperatures, lows tonight will likely drop off into the
upper 30s over northern areas where longer duration of clear skies
are expected before the mid and high level clouds move in. Not
confident in widespread frost given the current forecast lows and
the arrival of high clouds late tonight. There will also be a steady
northeast breeze through the night. That said though, would not be
surprised to see some patchy areas of frost in low-lying areas, but
don`t feel it will be widespread enough to warrant a headline given
the expected conditions.

Friday`s highs will remain very cool, especially across southern
areas where precipitation will be. Highs will likely be stuck in the
40s, with some 50s across northern areas.

.LONG TERM...(Friday Evening through Thursday)
Issued at 338 PM CDT Thu May 18 2017

A deep upper trough will pull out of the region on Sunday. With the
trough settled over the region Friday and Saturday, expect much
cooler than average temperatures to hang around. Additionally, a sfc
low will team with a lobe of the upper low to draw some precip into
South Dakota on Saturday. While instability looks limited, the
additional clouds and precip across the east will keep temps in the
40s for daytime highs.

Temps will recover on Sunday as skies clear and heights rise aloft.
The recovery will be short-lived, however. Another upper trough will
move into the Dakotas on Monday and linger through Wednesday.
Forecast temps are likely 10 to 15 degrees too high on Monday when
both the ECMWF and the GFS bring in precip on shortwave energy.
Tuesday is more uncertain since the ECMWF dries out SD, but the GFS
keeps continued precip and 850mb heights around +4C across the east.
Northerly flow and cloud cover, if not showers, could keep temps
suppressed east of the James valley. Cooler temps and more shower
potential seem to be trending on the latest model runs.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1239 PM CDT Thu May 18 2017

MVFR CIGs continue at KATY but look to be clearing out and/or
becoming SCT VFR later this afternoon. Otherwise, VFR conditions
will prevail through the rest of the afternoon and overnight
hours. Mid and high level clouds will gradually increase from the
south tonight as a storm system approaches. By Friday morning, low
end VFR CIGs are expected at KPIR, with -RA moving in also. By mid
morning, expect CIGs to go MVFR with -RA continuing.




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