Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Aberdeen South Dakota
1256 am CDT Friday Oct 31 2014
see below for an updated aviation forecast discussion.
High pressure dropping over the region...with much of the eastern
part of the County Warning Area now under clear skies. Still quite a bit of cloud
cover over the west...but it is getting pushed south rapidly...and
expect it to be out of the County Warning Area by midnight or so. No changes made
to winds or temperatures at this time.
short term...tonight through Saturday night
cold Canadian high pressure continues to sag south...with
northerly winds transporting much cooler and drier air into the
region. There is still a swath of stratus working southward
across the Dakotas this afternoon however...and this stratus
could have huge impacts on low temperatures tonight. The stratus is
eroding nicely on the front and back edges and is moving southward
pretty quickly. Plus with the extremely dry air moving
south...model 850 mb dewpoint depressions are on the order or 40
to 50 degrees...it should allow for clearing tonight...especially
across the eastern County Warning Area. This should be an optimal radiational
cooling set up...and low twenties and teens are forecast early
Friday morning. This all falls under the disclaimer that skies
Temperatures will remain well below normal Friday as well.
Additionally...the pressure gradient begins to tighten across
western South Dakota as the surface high moves east and the next
low pressure system approaches. BUFKIT soundings suggest wind
speeds across our County Warning Area will remain under advisory criteria for
Friday...although the far northwest County Warning Area could come close.
Alternatively...the pressure gradient shifts east and tightens
further on Saturday...a difference of around 20 mb across the
state...so a Wind Advisory may be needed across the County Warning Area on
Saturday. Given the persistent dry conditions and dead fuels
across the region...this may be a fire weather concern as well.
Long term...Sunday through Thursday
good agreement concerning upper level features through the
extended. Initially...flow is dominated by ridging aloft...with
an upstream shortwave. Thus...low level flow will be dominated by
warm air advection with 850 mb temperatures +1 to +2 Standard
deviations above climatology. Westerly low level flow from along and
west of the Missouri Valley suggests temperatures back into the
60s...while the rest of the County Warning Area struggles with a more
southeasterly component. West/northwest flow follows with cooler
temperatures till the next wave develops around middle week.
Best forcing with any of these features ends up north and south
of the County Warning Area...so for the most part the trend continues to be a dry
06z tafs for the kabr...Katy...kpir and kmbg terminals
An area of MVFR ceilings will exit the western County Warning Area between 06z and
08z...leaving clear skies over the entire County Warning Area for the remainder of
the overnight hours. Strong northerly winds within the lowest
2000ft above ground level /while surface winds are basically light and variable/
lends support to low level wind shear potential for the next few
hours at kabr and Katy. Southeasterly winds will increase into
the 15 to 25 miles per hour range across the western County Warning Area Friday afternoon and
evening...affecting kmbg and kpir. VFR conditions will prevail
through the day Friday.