Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 220851

Area Forecast Discussion
National Weather Service Aberdeen SD
351 AM CDT Sat Apr 22 2017

.SHORT TERM...(Today through Monday Afternoon)
Issued at 350 AM CDT Sat Apr 22 2017

High pressure today/tonight and Sunday will keep us dry, and as it
shifts to the south, will also be responsible for milder air moving
in ahead of a lee low. 850mb temperatures warm today from an initial
starting point of between +3 and +5C to +7 and +9C this evening -
with warm advection continuing overnight in southwest flow in the
low levels. This is ahead of a backdoor front which will bear
watching as most guidance stalls this feature just north of the
state line. Sunday 850mb temperatures increase to +9 and +15C,
however just to the north 850mb temperatures drop precipitously. If
the front tracks any farther south, current high temperatures will
need to be dropped back, however most guidance has settled on the
state line as the stalling point for this front.

A lee low develops out ahead of a weak wave. This feature will bring
moisture to the region Sunday night/Monday, although QPF will be
limited. More importantly is this low will link with the colder
airmass to the north, and by mid day Monday, colder air will be
moving in across the western half of the state.

.LONG TERM...(Monday Evening through Friday)
Issued at 350 AM CDT Sat Apr 22 2017

The 00Z suite of deterministic model solutions appear to start the
period off with a somewhat consolidated upper steering flow, namely
nearly zonal flow with very broad (baggy) longwave troughiness
forecast to be sprawled out over the western two-thirds of the
CONUS, with more than one noteworthy mid-level shortwave trof
passing through it. By mid-week, the GFS, ECMWF and Canadian models
are all suggesting some degree of split flow sets up again, which
the models typically have trouble resolving with any semblance of
comparative agreement. One primary signal that seems to be falling
out of the 00Z solutions is the chance for precip anchored on
Tuesday/Tuesday evening and then again, perhaps, right around the
tail end (or just outside the temporal range) of the current
extended forecast. Another primary signal is, compared to the 00Z
solutions of 24 hours ago, these longer range GSM solutions have
trended colder for temperatures at 925hpa and 850hpa all throughout
the period. Tuesday daytime mixing (925hpa) temps do not appear to
rise above +3C in any of the deterministic models. The 00Z NAEFS
Ensemble S.A. Table shows 850hpa temps at or below one standard
deviation below climo normal from 06Z Tuesday all the way to 12Z
Saturday before "improving" to half a standard deviation below
normal for the weekend into the first day of May. Superblend
guidance this morning generated surface winds either from the north
or with some component of northerly direction in it for the entire
forecast period (Monday night through Friday), which lends some
credibility to the idea that low level cold air, and dry air,
advection should be influencing the temperature forecast for the
whole week. Currently, Superblend guidance appears to be too warm
for pretty much the entire period, based off those 925hpa temps and
some of the various 00Z max/min T solutions and their bias
corrections when fed through the SCAVEC analysis tool. For now, was
able to collaborate a partial adjustment down in temperature for
Monday night and Tuesday.


.AVIATION...(For the 06Z TAFS through 06Z Saturday Night)
Issued at 1236 AM CDT Sat Apr 22 2017

Other than some potential for radiation valley fog toward sunrise,
it should be vfr at all terminals through Saturday.




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