Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 211123
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
623 AM CDT Sat Apr 21 2018

.SHORT TERM...(Today and Tonight)
Issued at 320 AM CDT Sat Apr 21 2018

We remain on the northern periphery of a slow moving closed low
tracking across the Central Plains. Ceilings remain at or above
8kft, and returns across the area are light so mostly virga. The
slow motion of the system, combined with light winds at cloud level,
means we will remain under cloud cover through the majority of the
day and into the overnight hours. This means temperatures will
struggle with the lack of insolation, though given morning temps in
the upper 30s and low 40s it shouldn`t be too much of a stretch to
reach 50. Readings overnight should remain mild though some clearing
could allow a few locations to bottom out into the 20s.

.LONG TERM...(Sunday through Friday)
Issued at 320 AM CDT Sat Apr 21 2018

At the start of the long term period, the area will be between
the upper low moving east out of the Central Plains and a surface
low located in central Saskatchewan.  The surface low in
Saskatchewan will move east to Hudson Bay through Monday while
slowly dragging a surface trough west through the western Dakotas
and into the CWA on Monday. Overall, should be a couple nice days
on Sunday/Monday. Expect some clouds along that trough on Monday
(likely along the SD/ND border and another separate area near
Sioux Falls left over from departing upper low) but also the
warmest air of the season ahead of it (850mb thermal ridge ahead
of trough). Expect highs to be the warmest of the season on
Monday and rise into the mid-upper 60s and a few degrees warmer
than Sunday.

Compared to yesterday, the shortwave driving the Monday night and
Tuesday system appears to be more diffuse in the deterministic
models, in addition to becoming separated from the main flow and
shortwave trough moving into the Great Lakes.  This is leading to
lower confidence both on timing and precipitation amounts as the
shortwave now looks to drop more to the southeast Monday night
into Tuesday. This recent trend is leading to a significant
spread in the ensemble members on the amount of precipitation
with the system.  GEFS plumes showing anywhere between 0.08 and
1.57 inches at KPIR and no real clustering.  00Z ECMWF EPS
probabilities are generally in line with the deterministic
solution and keeping the QPF over the western half of SD and runs
the 50 percent probability of 0.1 inch of QPF running from
Pollock to Huron and higher percentages to the west (around 70-80
percent in Jones county). With the uncertainty, will follow a
general model consensus for PoPs/QPF and fine tune as things come
into better agreement over the next couple days. One other trend
is towards the lack of a defined closed surface low (still in
GFS/CMC deterministic runs) which leads to less confidence in
strong winds on Tuesday. If the closed low occurs, could see
gusts towards 30-35kts for a few hour period, otherwise values
will stay below 30kts.

After Tuesday, we transition to a northwesterly flow regime as
an upper ridge is in place over the Rockies and a series of
troughs move through eastern Canada and the eastern CONUS. This
will sweep a couple cold fronts across the area, the first on
Wednesday night and the next one towards the start of the
weekend. Still looks like there will be limited moisture
associated with the frontal passages, so only expect a brief
period of clouds and no precipitation. Temps will likely be near
or even slightly above normal for most days, although Thursday
behind the front will be slightly below normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday Morning)
Issued at 621 AM CDT Sat Apr 21 2018

VFR conditions for all terminals. Some light sprinkles at KPIR can
be expected for the next hour or two. Winds will be primarily from
the south/southeast today/tonight.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

SHORT TERM...Connelly
LONG TERM...SRF
AVIATION...Connelly


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