Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Aberdeen South Dakota
317 PM CDT Tuesday Jul 22 2014
Short term...tonight through Thursday night
Canadian surface high pressure building slowly east will continue
to bring mainly dry conditions...mostly clear skies and slightly
below normal temperatures through Wednesday. The models show the
large upper level high pressure area over the southwest US
remaining through the short term. A 500 mb ridge axis extending
northward from this upper high into central Canada will be knocked
down by a strong upper level low pressure area moving in from the
Pacific northwest and into southern Canada. Short waves coming
over the upper ridge from the west and across our region along
with an increasing low level jet Wednesday night and Thursday will bring in
chances of storms. For tonight...some of the operational models
and hi-res models were showing storms developing in the High
Plains late this afternoon and dropping southeast across western
South Dakota and maybe into central South Dakota later this evening and overnight.
Will leave out probability of precipitation for now as believe it will remain west of our
County Warning Area. Otherwise...winds will turn southeast into Wednesday and
increase some. The models also show the low level jet increasing into
Wednesday night and Thursday morning. With this focus and a return
of moisture and instability...have in decent chances of storms
for Wednesday night into Thursday. It looks like it will heat up
again out west on Thursday with highs in the 90s along and west of
the river. Some places will approach 100 degrees again southwest
of Pierre. Will keep chances of storms going into Thursday night
as a surface front moves in from the west.
Long term...Friday through Tuesday
Models continue to show a large upper low dropping south into the
Great Lakes region for the latter half of the weekend. This will
allow a shot of cooler air to drop south over the northern plains
and affecting the eastern Dakotas. After a couple warm and
seasonable days in the 80s Friday and Saturday...Sunday will see
highs more than likely drop back into the 70s for eastern portions
of the forecast area.
Precipitation chances a bit more unclear in the extended period
with no real significant waves to hang your hat on. Generally
accepted allblend pop grids at this point.
18z tafs for the kabr...Katy...kpir and kmbg terminals
VFR conditions will persist through the taf forecast period.
Towards 12z Wednesday there may be a few isolated -shra/-tsra over
western South Dakota...possibly as far east as central South Dakota. Overall
confidence in eastward extent is very low so will leave mention
out of kmbg/kpir tafs at this time.