Area forecast discussion...updated
National Weather Service Aberdeen South Dakota
839 PM CDT Tuesday Jun 18 2013
Update...
no major updates planned this evening...will keep chance thunder West
River for late tonight. Updates out soon.
&&
Previous discussion...
short term...tonight through Thursday night
With high pressure over the eastern Dakotas currently conditions
are fairly stable across the County Warning Area. Main forecast challenge will be
the area of low pressure moving off The Rockies this week and
associated thunderstorm chances.
Tonight...greatest instability continues to be across far western
South Dakota where southerly flow ahead of the trough is providing an
environment conducive to tstorm formation. The low level jet increases to
around 25 kts this evening along and west of the Missouri River.
Combined with 1500 to 2000 j/kg of cape and limited cin...isolated
strong to severe storms may drift into the area from the Black
Hills.
Wednesday...a shortwave moving across the state will help kick off
some storms by Wednesday afternoon. While it seems to be somewhat
overdone the NAM does place 4000 j/kg of cape across the east
Wednesday evening. With a low level jet increasing to 25 to 35 kts and
almost no cap storms should easily begin to fire off as soon as
convective temperatures are reached.
Thursday...this is when the forecast become much more challenging.
Models are differing on timing the progression of the low across the
region. The NAM is considerably faster than the GFS. This would
impact the areas of greatest instability and any inhibition. At
this time it appears that the east still has a good chance of
seeing severe storms. 700 mb temperatures on the GFS from +10 to +13 from
the James River east and over 3000 j/kg of cape along with a 30 knots to
40 knots low level jet may lead to an active afternoon and evening.
Long term...Friday through Tuesday
Upper pattern features southwest flow aloft during the extended
period with several waves of energy crossing the northern plains.
It looks to be a rather active time period with several chances
for showers and thunderstorms. Surface low will also become
established over South Dakota/Nebraska Friday and Saturday with ample low level
moisture surging northward into the area. Surface dewpoints could
reach and exceed 70 degrees by Friday afternoon over the eastern
County Warning Area. Plenty of instability and shear in place as well...although
700 mb temperatures soar to around +14 to +16 across the eastern
County Warning Area...slightly cooler farther west. This cap should help suppress
convection given the lack of any real strong shortwave during the
daytime. By Friday night...middle level temperatures cool a few degrees as
weak impulse pulls out of The Rockies and moves through the
Dakotas. With low level jet cranking up...could see better storm
chances Friday night into Saturday morning. Will see storm chances
through the day Saturday as well as surface low lingers across the
area and will likely be dealing with outflow boundaries and the
main synoptic boundary as well. The stronger upper wave finally
kicks east by Sunday with a surface front sliding east through the
County Warning Area. This will switch winds to a westerly direction and bring in
drier air...and also a weak surface high moving through Sunday night.
Even though small chances remain in the forecast on Sunday...it
appears the bulk of the action will be Friday through Saturday
night.
&&
Aviation...
00z tafs for the kabr...Katy...kpir and kmbg terminals
VFR conditions are expected through tonight.
&&
Abr watches/warnings/advisories...
South Dakota...none.
Minnesota...none.
&&
$$
Update...tdk
short term...wise
long term...tmt
aviation...tdk
Weather.Gov/Aberdeen
