Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Aberdeen South Dakota
741 PM CDT Thursday Sep 18 2014
overall the forecast looks okay. Stratus developing the Central
Plains should make its way up into the eastern Dakotas late
tonight...early Friday. With high dewpoints in place the predicted
lows look pretty good. No major updates planned.
short term...tonight through Saturday night
an upper level low pressure trough and associated surface low
pressure area will make their way along the Canadian border through
Friday evening while a surface cold front pushes in behind. Until
then for tonight...expect the surface pressure gradient to stay
tight and winds to stay up mainly in the east as low level
moisture increases. Thus...expect stratus clouds to form mainly
across the east tonight with mild overnight lows around 60 to 65
degrees across the County Warning Area. With the upper level low pressure trough
sliding into the region...a jet streak will favor upper level lift
over our region into Friday night. At the surface...the winds will
decrease from the south tonight and slowly turn southwest...west
and then northwest into Friday evening as the cold front passes.
The focus/low level lift along this boundary will be weak.
Therefore...with only weak low and upper level lift along with
warm air aloft/capping...have only slight chances of
showers/storms with this system as it moves through the region.
May have to take them out completely in later forecasts as all of
the models were only showing little if any quantitative precipitation forecast. Expect the best
chance of showers/storms to be south of our County Warning Area Friday night with
better lift along the cold front. Friday should also be a very
warm day across the County Warning Area with highs in the 80s.
Friday night and Saturday will bring a slight cool down as cold air advection
dominates with highs mostly in the 70s under mostly sunny skies on
Saturday. The mixing layer will be deepening through Saturday with
increasing northwest winds. Therefore...expect breezy/windy conditions
for the County Warning Area on Saturday. A short wave trough dropping across the
eastern part of the region Saturday and Saturday night may end up
bringing some showers far east in our region. At this time...left
it dry. Saturday night will cool off as winds fall off under clear
skies as surface high pressure pushes in from the west.
Long term...Sunday through Thursday
tricky upper flow pattern appears to set up next week past
Sunday/Sunday night. Northwest flow aloft and low level cold air advection is in
play as surface high pressure builds into the region for
Sunday/Sunday night. Meanwhile...the upper circulation out over
northern California is supposed to be cut off from the rest of the
polar westerlies jet stream winds and slowly meander its way over
into the central/northern plains beneath an upper level ridge by
middle-week next week. This is a dying/occluded upper circulation
that should be spinning down over time with little if any surface
pressure reflection. Nevertheless...allblend continues to
populate extended pop grids with chance and slt chance
probabilities for precipitation. And...given the synoptic scale
set-up of return flow and notable 850hpa moisture streaming back
northward into the region...seems The Table will be set for a few
showers or storms to develop next week. As far as temperatures
go...Sunday should be the coolest day in the extended with a slow
and steady warm up right on through Thursday.
00z tafs for the kabr...Katy...kpir and kmbg terminals
VFR conditions this evening will be replaced by a deck of IFR
clouds from the south late tonight into Friday morning. Then on Friday
some improvement is expected from west to east as a frontal
boundary shifts the winds to westerly and helps usher out the low
clouds. The wind should decrease some overnight.