Area Forecast Discussion
Issued by NWS Aberdeen, SD
FXUS63 KABR 300207 AAB
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
907 PM CDT SUN MAY 29 2016
Issued at 855 PM CDT SUN MAY 29 2016
The synoptic-scale set-up overnight tonight favors late night
elevated shower/thunderstorm development. Mid-level waa is in
effect while a low level jet developing up into central and south
central South Dakota will continue to pump low level moisture
northward into the region. Only needed to make minor
modifications to pops/wx grids as precipitation chances were
already mentioned for the overnight. The 18z nam /and to a lesser
extent the 18z gfs/ showcased as much as 750-1000j/kg of elevated
CAPE tonight on the nose of the low level jet /forcing for
ascent/, as the LLJ gradually works northward across the cwa.
Would not be surprised if a couple storms became strong to
marginally severe, mainly at or after 07z tonight.
UPDATE Issued at 641 PM CDT SUN MAY 29 2016
See below for an updated aviation forecast discussion.
.SHORT TERM...(This Evening through Monday Afternoon)
Issued at 329 PM CDT SUN MAY 29 2016
Surface high pressure will exit the region to the east
tonight...ahead of an approaching low pressure system and associated
upper level shortwave. There may be a few showers or storms across
the western and southern CWA this evening ahead of the
system...though some of the models have backed off considerably on
this. Therefore...will keep pops fairly low. Attention then turns to
Monday when the system will begin to push across the state. The
front looks to be situated over the western CWA at 00Z
Tuesday...with most of the reflectivity models showing a line of
storms over the Missouri river. The atmosphere will become very
unstable quickly on Monday...with MUCAPE values in excess of 3000
J/KG by 18z. Lapse rates of 6.5 to 7.5 C/km and the beginnings of a
25 to 35 knot low level jet will also begin by midday. Dewpoints of
55 to 60 degrees will be approaching from the south. One limiting
factor will be marginal deep layer shear values of only 25 to 35
knots...but low level shear around 15 knots may make up for that.
Slight risk has been issued by SPC...so will introduce low pops in
the morning...then increase them significantly during the afternoon
hours...especially across the west with large hail and gusty winds
likely being the main storm threats.
Low temperatures tonight will be in the lower to mid 50s...with
highs on Monday in the upper 70s to lower 80s.
.LONG TERM...(Monday Evening through Sunday)
Issued at 329 PM CDT SUN MAY 29 2016
Severe weather should be rolling across eastern SD Monday evening as
the front pushes east. Models are in good agreement of a linear
system moving across the east during during this time and as
expected SPC has the area in slight risk.
The main system will kick through by Tuesday morning with the dry
slot in place across the forecast area. northwest winds will
increase behind the front and conditions will be relatively dry.
However, as the low moves across North Dakota Tuesday night and
Wednesday area could see a few shower/thunderstorms in the wrap
around moisture. Wednesday will be the coolest day of the week.
After the system ejects by Wednesday night, the mean ridge across
the west will rebound with rising heights across the forecast area.
There does appear to be any good forcing mechanism in place for
storms into next weekend. Expect warming temps and mostly dry
conditions into the weekend.
.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 641 PM CDT SUN MAY 29 2016
Except for IFR visbies/cigs in heavy thunderstorms tonight and
Monday, VFR will be the prevailing weather conditions across all
four terminals during the TAF valid period. The table will be set
for isolated to scattered night-time /elevated/ showers and
thunderstorms across central and northeast South Dakota from late
this evening /appx 04z/ through mid-morning on Monday /appx 15z/.
While most of tonight`s convective activity will be sub-severe, a
few storms could produce hail. There is a greater probability for
scattered to numerous strong to severe thunderstorms later in the
afternoon and on into the evening hours on Monday.