Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 191804 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
104 PM CDT Fri May 19 2017

Issued at 1254 PM CDT Fri May 19 2017

See below for an aviation forecast discussion for the 18Z TAFs.

UPDATE Issued at 859 AM CDT Fri May 19 2017

Made a few minor tweaks to the today period forecast. Increased
skycover all the way to overcast everywhere and will leave it that
way until satellite shows breaks in the cloud-cover. This has
resulted in the shaving off of a degree or two most everywhere on
today`s high temperature forecast. Also, based on current
radar/satellite loop, and forecast reflectivities in all the hi-
res CAM output, adjusted the rest of today`s pops coverage/timing
and associated "trace to less than one-tenth of an inch" qpf
forecast accordingly. Still looks like rain will have a tough time
(per 12Z KABR RAOB) reaching all the way to the ground today as
it tries to work northward given all the remarkably dry air in
place between the surface and 500hpa. Probably a good cut-off for
the rain-no rain line by late this afternoon is U.S. Highway 212.
Updates are out.

UPDATE Issued at 625 AM CDT Fri May 19 2017

See updated aviation discussion below.


.SHORT TERM...(Today through Sunday Afternoon)
Issued at 339 AM CDT Fri May 19 2017

Scattered light returns continue to move northwards across the
forecast area, associated with mid level ascent/moisture, but also
struggling to overcome the fetch of low level dry air, with dewpoint
depressions upwards of 20 degrees F. Thus, have scaled back POPs for
most of the morning/today periods. Temperatures have stabilized due
to the broad area of mid/high clouds, and with the cloud cover
today, expect that high temperatures will be within 5-10 degrees of
current readings. Current high forecast is not far off of record low
high temperatures thanks to 925mb temperatures 2 standard deviations
below climo.

Tonight, the upper low begins to move out of Colorado, with the
surface low deepening across Kansas. The Canadian high pressure
center also migrates towards southeast Canada as well. Best upper
forcing still won`t arrive until Saturday however, and that is when
blended guidance jumps into the higher orders of POPs. The focus for
TROWAL precipitation will mainly be along and east of the James
valley region. The NAM during that time has a cold bias, and
profiles suggest the freezing level gets fairly close to the
surface. SREF and GFS are a couple of degrees C warmer. Blended
guidance supports mainly rain, though again with such low freezing
levels, can`t rule out some flakes making it to the surface or a
light accumulation of wet snow. Ground temperatures are warm enough
that any snow will melt off fairly quickly. Again, current high
temperature forecast is a few degrees off record low high

Precipitation and cloud cover continue into Saturday night. With
such cold daytime temperatures, will need to address the frost
potential in future updates. The most likely part of the CWA at risk
is central and western counties, where clearing and a weak gradient
are more likely to be prevalent.

.LONG TERM...(Sunday Evening through Thursday)
Issued at 339 AM CDT Fri May 19 2017

A broad upper level trough will be over the region Sunday night
through Tuesday night. The remainder of the period will feature
northwest flow aloft as a ridge builds over the Rockies.

Sunday night looks dry under the influence of weak high pressure. A
frontal boundary associated with low pressure spinning over the
Great Lakes will drop over the region Monday, likely becoming the
focus for precipitation. High pressure moves through again on
Tuesday before another low pressure system drops out of Canada and
skirts the area to the east. Cannot rule out a few showers with that
system before high pressure and dry conditions return at the end of
the period. Little in the way of instability, and shear is minimal
during the times precipitation is expected, so will keep the
precipitation mention as just rain showers for now.

Temperatures will still be a bit cool early in the period, with
highs in the 60s Monday and Tuesday, then will see a return to near
normal temperatures, with highs in the 70s Wednesday through Friday.
Overnight lows in the 40s will be common.


.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.




SHORT TERM...Connelly
LONG TERM...Parkin
AVIATION...Dorn is the U.S. government's official web portal to all federal, state and local government web resources and services.