Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 031427 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
927 AM CDT Mon Oct 3 2022

Issued at 921 AM CDT Mon Oct 3 2022

No changes planned to the today period forecast. Plenty of clouds
around again today, with some isolated/scattered coverage of
mainly showers ongoing.

UPDATE Issued at 624 AM CDT Mon Oct 3 2022

See updated aviation discussion below.


.SHORT TERM...(Today through Tuesday Afternoon)
Issued at 314 AM CDT Mon Oct 3 2022

The main challenge in the short term period is precipitation
chances. An upper level low that has been spinning over the Northern
Rockies for the past few days will finally begin to eject eastward
today, with the main shortwave energy reaching the Dakotas/Nebraska
by the end of the day Tuesday.

At the surface, an elongated area of low pressure and associated
frontal boundary currently extends from central North Dakota to
eastern Colorado. This boundary will very slowly track eastward, and
will extend from northwestern Minnesota to southwest Kansas by late
Tuesday afternoon. This boundary, in association with the
aforementioned upper level shortwave energy, will be the focus for
scattered rain showers, keeping unsettled conditions going through
the entire short term period. The models are indicating about 500
J/kg of MUCAPE over mainly central South Dakota both this afternoon
and Tuesday afternoon, so cannot rule out some thunderstorm
activity, however no severe weather is expected.

High temperatures today will be in the 70s, with lows tonight mainly
in the 50s. Highs on Tuesday will be in the upper 60s to lower 70s.

.LONG TERM...(Tuesday Evening through Sunday)
Issued at 314 AM CDT Mon Oct 3 2022

Main concern in the long term is the high confidence of at and below
freezing temperatures expected Thursday overnight into Friday
morning, which will put an end to the growing season. Otherwise,
cooler than average temperatures continue for the end of the week.

Clusters are in agreement for the start of the long term with a
highly amplified 500mb ridge across the western US. This puts our
CWA in a strong northwest flow downside this ridge with a positively
tilted trough to our east/northeast. Within this flow, ECMWF
indicates the shortwave trough/cutoff low, that has been slow moving
to our west and its sfc cold front, will finally be pushing through
the CWA Wednesday, indicated by the models. NBM indicates slight-
chances (15-44%) of showers and thunderstorms east of the Missouri
River through Wednesday ~18Z. The s/w will be to our east Thursday
with the overall main pattern remaining the same into
Thursday/Friday. Cluster ensembles seem to diverge a bit towards day
7 with another trough moving over this ridge that would flatten it.
At this point only half of the ensembles show this. Surface maps
from GFS/ECMWF indicate a 1036mb high swinging down behind the
shortwave Wednesday-Thursday from the north. This high, along with
continuing northwest flow aloft, will make for some chilly
temperatures for the end of the week with overall highs up to 20
degrees below our average!

We will see a ~30-40 degree drop between Wednesday highs and lows as
the cold front pushes through. NBM highs for Wed are expected in the
70s with overnight lows in the mid/upper 30s to the lower 40s across
the CWA. Thursday highs only expected in the upper 40s to the lower
50s. Overnight lows Thursday into early Friday are forecasted to be
the coldest night with temps at or below freezing. NBM indicates
lows in the mid 20s to the lower 30s across the CWA. ECMWF/GFS (as
of now) indicate 925mb temps ranging from -1 to +3 degrees C and ~-3
to +1 degrees C at 850mb by 12Z Friday, which backs up this strong
CAA. Agreement between models this far out gives a higher confidence
that this will be the end of the growing season on Friday morning.
Temps look to rebound a bit heading into the weekend as this surface
high pushes southeast with sfc winds out of the south. NBM highs for
the weekend will top in the mid 60s.

Lastly, with the passing of the strong cold front and incoming
strong high, I did a blend of NBM 4.1/90th Wed 18Z-Friday 00Z as a
steeper pressure gradient looks noted by the deterministic models
with drier air moves in. Inverted V soundings up to ~850-700mb look
apparent by GFS bufkit both Wed and Thursday afternoon.


.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
Issued at 624 AM CDT Mon Oct 3 2022


For the most part, VFR conditions will prevail across the area
today and tonight. Scattered showers, and a few thunderstorms,
are possible this afternoon and evening. Breezy south winds will
occur across the area today, with some gusts in excess of 25 knots
possible. Winds will become light and variable tonight.




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