Area Forecast Discussion
Issued by NWS Little Rock, AR
FXUS64 KLZK 211712 AAB
Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
1212 PM CDT Tue Mar 21 2017
Have updated the forecast to adjust for current trends and
increase POPs and cloud cover across the NRN half of the state
through this afternoon. Otherwise...not expecting many changes
further south...with highs once again in the 80s in this region of
the state. Cooler conditions are expected north of this front
across NRN AR due to precip and increased cloud cover.
Have also updated to include the 18Z aviation discussion below...
VFR conditions are ongoing early this afternoon...even as some
SHRA/TSRA move over NRN sections of the state. A cold front will
drop south through this evening and overnight...with some SHRA and
TSRA possible along and behind this front. Expect lowering CIGS
behind this front as well...which will likely continue through the
end of this TAF period.
PREV DISCUSSION...(ISSUED 400 AM CDT Tue Mar 21 2017)
SHORT TERM...Today through Wednesday Night
Nearly stationary fntl bndry was draped acrs NRN AR early this mrng.
Other than a wind shift behind the fnt, there was no significant chg
in airmass on either side of it. Predawn temps were generally in
the the mid 50s to the mid 60s.
The short term models rmn in good agreement this mrng regarding fcst
trends ovr the next 24 to 48 hrs. The aforementioned fnt wl be the
focus of SCTD convection later today/tngt as a new upr lvl impulse
moves EWD acrs the area.
Clouds and rain chcs wl keep highs temps mainly in the 70s ovr the
NRN counties today. Meanwhile, contd SWLY winds and plenty of
sunshine wl result in another day of unseasonably warm temps with
highs in the lower and mid 80s.
The fnt wl eventually work further SWD acrs AR later tngt and on Wed
as another upr impulse drops SEWD into the FA. Best lift assocd with
the upr system wl be ovr NRN AR, with likely POPS in the fcst. Have
contd to indc a dcrsg trend in the rain chcs further to the S.
Incrsg NELY winds behind the fnt wl usher much cooler air into AR
later tngt and on Wed. Due to the shallow nature of the cooler
airmass, expect a good amounts clouds on Wed with little in the way
of rain chcs. Highs on Wed wl be a good 15 to 25 degrees lower than
today. Small rain chc wl return to mainly WRN AR later Wed night as
the fnt begins to lift back NWD into AR. This wl be in response to a
new storm sys forming over the Plains States.
LONG TERM...Thursday through Monday
The long term period looks to be a fairly active one, with a strong
line of thunderstorms forecast to move through Friday evening, and
two other systems forecast for the first half of next week.
The much talked about, and primary, concern for this forecast period
though is the system for Friday. Models are still in good agreement
with regard to forecasting a strong line of storms moving into
western Arkansas during the late afternoon or early evening hours.
Expect the initial line of storms to be east of the forecast area
by, or shortly after, daybreak Saturday morning. Like previous
shifts, high PoPs are in the forecast but have not gone quite 100%
yet. It will rain, but due to possibility of timing changes, will
leave it shy 100% for now.
Regarding severe chances, the thinking remains that this will be
primarily a wind threat situation with a squall line moving through.
Guidance continues to indicate only marginal instability along/ahead
of this line, with less than 1,000 J/kg of MU CAPE forecast.
However, cross sections from across the state reveal models
forecasting upwards of 70kt winds below 10k ft AGL and 50-60kts of
bulk 0-6km shear. Despite marginal instability, shear will be
sufficient enough for some damaging winds. While it`s hard to say
there will be no spinups along the line for possible QLCS type
tornadoes, the overall threat for tornadoes is on the low side. The
same goes for hail.
Behind the line, on Saturday, more convection will be possible. The
combination of cooling aloft and some partial clearing of skies will
result in surface-based instability climbing upwards of 1,000 J/kg.
Will maintain shower & thunderstorms mention for Saturday as a
result. Coverage should be scattered in nature, and there may even
be some hail, though the severe threat will be low.
The upper trough responsible for the Fri/Saturday convection will
shift east of the region by Saturday evening. Short-lived and weak
upper ridging will build overhead on Sunday but another shortwave
trough will approach from the west Sunday evening and should bring
scattered showers and thunderstorms back to Arkansas late Sunday
night into Monday morning. Another trough will follow on Tuesday.