Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 200900

Area Forecast Discussion
National Weather Service Aberdeen SD
400 AM CDT Sat May 20 2017

.SHORT TERM...(Today through Monday Afternoon)
Issued at 355 AM CDT Sat May 20 2017

Today: Light returns showing up on regional radar, however CIGS
remain fairly high and PIR ABR ATY and MBG all have dewpoint
depressions on the order of 10 to 15 degrees. That said, as the low
deepens over Nebraska, flow becomes more easterly and we should
saturate out the low levels. TROWAL moisture will wrap back into
the CWA through the majority of the today period, though the focus is
across eastern South Dakota/western Minnesota, and west river
counties will experience more hit/miss shower activity. High
temperatures in the east are unlikely to budge much today, while
more filtered sun will allow for readings to top 50 out west.

Tonight: It gets complicated. Lets address P-TYPE first. NAM has a
cool bias, however both it and the Canadian suggest some light snow
accumulation as the system treks northeast, with TROWAL moisture
continuing to wrap back into the eastern CWA. Added mention of
Rain/Snow, with the focus over the higher elevations of the Coteau.
This is just a novelty as ground/air temperatures are too warm for
snow to stick. Winds will remain breezy in the eastern CWA as the
surface low moves across Iowa/Minnesota, so despite lows in the 30s,
frost should not be a problem.  Its a different situation in western
and central counties. With such a cool airmass - 925/850mb
temperatures 2 standard deviations below climo - and cloud cover
during the day limiting warming, we expect high temperatures to
struggle into the 50s. The next question will be the degree of
clearing overnight, which is highly uncertain as we lack a well
defined high center. NAM BUFKIT profiles take much of the night to
completely dry out and GFS 500/700/850mb RH also remains high
through the evening and early overnight hours before some gaps of
drier air mix in. Thus, only expecting partial/patchy clearing.
Despite this, the cool start to the evening, along with light
winds supports a threat for patchy frost.

Sunday features continued cool temperatures and breezy northwest
winds but soundings continue to dry out, so mid/late may sunshine
should support highs in the 60s.

Sunday night/Monday: A secondary shortwave drops out of Canada.
With northwest flow, and cooling temperatures aloft - steepening
lapse rates will lead to elevated shower activity. Mixed winds in
BUFKIT soundings top out around 20-30kts.

.LONG TERM...(Monday Evening through Friday)
Issued at 355 AM CDT Sat May 20 2017

A broad mid level trough will be over the region Monday night, with
shortwave energy in the vicinity through Tuesday evening. Ridging
then sets up through Thursday night before the flow becomes
southwesterly and a series of shortwaves track across the region
through the end of the period.

At the surface, high pressure will drop southward over the western
Dakotas Monday night, then shifts eastward through the day Wednesday
ahead of a trough digging down the lee of the Rockies. As the trough
slowly shifts eastward, precipitation chances will increase by late
in the week and continue into the weekend. Instability and shear
appear to be minimal at this time, so will not include thunder and
will keep the precipitation mention as just rain showers.

Temperatures will still be a bit cool on Tuesday, with highs mainly
in the 60s. Will see a return to the 70s mid to late in the week,
with Thursday likely being the warmest day of the period. More cloud
cover and potential precipitation will bring temperatures back down
into the 60s on Saturday. Overnight lows will be mainly in the 40s.


.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1227 AM CDT Sat May 20 2017

VFR conditions are expected overnight. As rain begins to spread over
the region on Saturday, KABR/KATY/KPIR will fall to MVFR/IFR cigs.
Vsby will also be reduced in heavier showers.




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