Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Little Rock Arkansas
542 PM CST Thursday Dec 12 2013
moisture will gradually increase tonight...with precipitation
expected around 12z across the west. Have added a fzrapl mix
across the north and west...changing over to all rain by middle day.
Across the central and southeast...kept mix as rapl for just a few
hours. All rain is expected for this taf cycle. MVFR conditions
will prevail...but did include some scattered IFR conditions. Low level wind shear
is possible tonight into Friday morning.
Previous discussion... /issued 225 PM CST Thursday Dec 12 2013/
Short term...tonight through Sunday night
latest surface analysis shows surface high pressure sitting
basically on top of the forecast area. Temperatures have responded
into the upper 30s to upper 40s as a result with near full sunshine.
Attention will now turn to a closed upper low sitting over over
Southern California and clearly visible on moisture channel imagery
at this time.
System will be kicked to the east fairly quickly over the next day
or so by a fast moving Pacific trough. These two systems will merge
into one resulting in rather unsettled conditions for the forecast
area starting Friday and lasting through middle day Saturday. Models
remain in agreement as far as the timing is concerned and basically
slow down its arrival somewhat and all precipitation will be removed
from the tonight period and pushed back several hours over the east
during the day Friday.
The slower onset on the precipitation will allow temperatures to
warm just enough to bring mainly a rain event to the area. Model
forecast soundings do show dry air over the area early Friday and
wet bulb effect could bring some sleet to central sections of the
state with thermal profiles indicating some freezing rain across the
north. GFS solution remains the most aggressive with this winter
precipitation scenario while NAM/sref not so much. As a
result...will continue to hold onto some wintery precipitation but a
changeover to just rain is expected with perhaps a brief period of
winter weather across the north early Saturday as the system pulls
Only minimal ice accumulations/impacts are expected... the
GFS does pan out...a Winter Weather Advisory may be necessary across
parts of the north but this would be up to later shifts to decide.
Precipitation will come to an end Saturday night before another
shot of colder air returns but it appears to be short lived this go
around with temperatures rebounding nicely in the extended period.
Long term...Monday through Thursday
the extended forecast will be characterized as dry with near normal
temperatures. Monday has the surface high pressure system off to the
south with a south wind flow back in to Arkansas...helping warm
temperatures back much closer to normal values. Tuesday to possible
Wednesday has a weak cold front sagging into Arkansas but brings little
with it but some clouds and a wind shift to the area. The upper west to
northwest flow takes much of the cold air and keeps it north and moves it
east of Arkansas. The surface high pressure behind the front moves quickly
east to southeast...and a light south flow comes back to Arkansas later Wednesday to
Thursday...helping temperatures rebound. Thursday still is dry with
warming temperatures while a developing surface low pressure system
develops over the Western Plains and gradually moves east. This
system will effect the weather for Friday...with possible
precipitation. Used a blend of Euro and GFS...but a solution closer
to GFS at this time.