Scientific Forecaster Discussion
fxus64 klzk 260851
Area forecast discussion
National Weather Service Little Rock Arkansas
350 am CDT Fri may 26 2017
Short term...today through Saturday night
Surface low pressure was centered over north-central OK early this mrng.
As a result, S/southeasterly wind flow was noted over AR, with predawn temps
mainly in the 60s. Low lvl moisture/clouds wl cont to advect into
the region today as the sfc low slowly moves closer to the state.
Much of the area wl rmn dry today, except ovr north Arkansas where a
developing warm front could set off widely scattered shra/tsra. Appears
wind speeds wl rmn below lake Wind Advisory criteria today.
The aforementioned surface low wl weaken as it passes north of Arkansas
tonight. An assocd frontal bndry wl become nearly stationary to the
north of Arkansas heading into Sat as the upr flow pattern rmns zonal. A
series of upr impulses wl track along the stalled fnt heading into
the weekend, providing a focus for additional convection.
Convective trends for the Sat/Sat ngt timeframe rmn problematic.
Model data cont to indc a strong capping inversion in place ovr much
of the forecast area on Sat, even with SBCAPE values in the 3-4k j/kg range Sat
aftn/early evening. Instability wl also be enhanced Sat aftn with
sfc temps warming well into the 80s and dewpoints in the lower and
Will all that said, it still appears that convection wl form to the
northwest of Arkansas Sat evening as the front begins to make a push to the southeast.
This scenario would favor a complex of storms eventually working
into Arkansas later Sat night into sun, with damaging winds being the
primary concern. However, the models this mrng have slowed down the
progression of the front into AR, which would tend to shift the
focus of organized convection just beyond this fcst pd.
Long term...Sunday through Thursday
The cold front will be dropping slowly southeast into the state at the
start of the long term period...which is a tad slower than in
previous Med-range model guidance. Looks like convection will be
ongoing on Sun morning along/ahead of the front over the northern/northwestern
third of the County Warning Area. While the overall severe wx threat will be lessening
during Sun morning...a few strong to severe storms may remain
possible...especially if a mature complex and associated cold pool
is progressing over portions of the County Warning Area. Damaging winds will be the
primary threat with the strongest storms on Sun morning.
As the front progresses southeast across the County Warning Area sun...redevelopment of
rain showers/thunderstorms and rain will be possible during the afternoon/early evening hrs
sun along/ahead of the cold front. Depending on the speed of this
front by this time...the best chances for seeing strong to severe
storms will shift to the southeastern half to third of the state...where
instability will have increased with daytime heating. Depending on
the resulting storm Mode...cape profiles suggest very large hail and
damaging winds as the primary severe wx threats given the thick cape
profile and dry air in the hail growth zone. This will be especially
true for any cluster or isolated cells. If the storm Mode
transitions to a bowing line segment or organized complex...damaging
winds will then be the primary threat. The tornado threat looks
limited at this time given the low level shear profiles...but an
isolated tornado could still be seen.
Expect the front to drop southeast of the state by late Sun night and Mon
morning...with the precip chances decreasing. Generally dry
conditions will be seen for Tue into Tue night...but chances for
rain showers/thunderstorms and rain return for late Wed into Thu as a new upper level
shortwave trough approaches from the west.