Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 192053
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
353 PM CDT Fri May 19 2017

.SHORT TERM...(This Evening through Saturday Afternoon)
Issued at 352 PM CDT Fri May 19 2017

Forecast challenges include evolution of cloud cover overnight and
its effects on temperatures and frost potential, as well as areal
coverage/timing of precipitation and precipitation amounts late
tonight and on Saturday.

Currently, skies are mostly cloudy to overcast and temperatures have
climbed into the 50s for most areas in this CWA. Where localized
areas of light rain continue, temperatures are still in the mid to
upper 40s. Winds are running generally out of the north or east at
about 5 to 15 mph.

Have had a tough time getting rain to reach all the way down to the
ground today, what with all the dry air in place below 12kft. It`s
far more probable that the area of low pressure lifting out of
Colorado will overcome this dry air to produce some widespread
measurable by Saturday morning over the eastern half of South
Dakota, including this CWA. But first, will need to closely monitor
satellite/skycover trends this evening to see if the clouds thin out
or dissipate over north central South Dakota where the coldest
possible temperatures (in the mid to upper 30s per CoOp Obs) could
set up for a third night in a row. Based on the forecast conditions
tonight, the frost smart-tool generated "areas of frost" over Corson
County for more than 3 hours late tonight/early Saturday morning.
With BIS forecast office issuing a frost advisory for tonight
bordering South Dakota, opted for a Frost Advisory for Corson
County.

By 12Z Saturday, most GSM output and pretty much all the available
hi-res CAM solutions were generating a northward and westward-
pivoting band of rain working into this cwa, which then hangs out
over the cwa all day Saturday. Precipitation amount forecast
guidance has much of northeast SoDak picking up between 0.50in-
0.75in of rainfall from this system. Further west (west of the James
River valley), amounts taper off to more like a tenth of an inch to
0.25in of rainfall heading towards the Missouri River valley.
Temperature recovery will be difficult to come by on Saturday,
except over portions of north central SoDak where little to no rain
is forecast.

.LONG TERM...(Saturday Evening through Friday)
Issued at 352 PM CDT Fri May 19 2017

The period begins with a surface low pressure system moving into the
Great Lakes region. Showers will likely continue on the backside of
this surface low and associated upper level trough Saturday night
through Sunday. Eastern and northeastern SD has the best potential
of seeing pcpn Saturday night. A few areas could see light snow
Sunday morning. Patchy frost will be possible west of the James
River Sunday morning assuming clouds are able to clear. While the
surface pressure pattern is fairly weak on Sunday, model soundings,
especially the NAM, suggests deep mixing with gusty winds possible.

A weak area of low pressure will track across the region Monday
through Monday night. This system will have limited instability with
weak showers and thunderstorms possible. Upper level ridging and a
surface high pressure will build into the region Tuesday and
Wednesday with dry conditions expected. The surface high pressure
drifts southward by Thursday with much above normal temperatures
possibly moving into the region. All the Raw model guidance suggest
highs on Thursday will warm into the 80s. These readings are 5 to 7
degrees warmer than Superblend. Thus have increased highs on
Thursday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1254 PM CDT Fri May 19 2017

With the exception of KPIR, expect VFR conditions to prevail
across the area over the next 6 hours, and probably for much of
the next 18 hours. Areas of light rain (and subVFR cigs) will
continue to affect KPIR this afternoon. KATY may see a little bit
of this light rain for a few hours by late afternoon persisting
into early this evening. At or after 12Z Saturday, KPIR, KABR and
KATY will likely see subVFR cigs spreading over them as light
rain begins to sweep north and west across the region. Vsbys
could also briefly dip below VFR with the precipitation Saturday,
especially at KATY.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory from 2 AM to 8 AM MDT Saturday for SDZ003.

MN...None.
&&

$$

SHORT TERM...Dorn
LONG TERM...SD
AVIATION...Dorn



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