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Area forecast discussion...updated 
National Weather Service Little Rock Arkansas
458 PM CST Thursday Feb 11 2016

Discussion...

Updated to include the 00z aviation discussion below...

&&

Aviation...

Winds will lessen overnight...with generally less than 10 kts
expected. Some locations may see winds become variable...but
another frontal boundary will move through the state on Friday...with
nearly winds increasing once again. However...should see winds
remain at less than 10 t0 15 kts...with some higher gusts.

&&

Previous discussion... /issued 311 PM CST Thursday Feb 11 2016/

Short term...tonight through Saturday

Cold front has continued to push south and move through the state
today with winds turning out of the northeast. With the
front...temperatures varied a bit through the state despite mostly
clear skies being seen. Temperatures ranged from the middle 40s across
the north to 70 degrees in south Arkansas.

Overnight winds will become calm and temperatures will fall to near
seasonal normals with temperatures reading from the upper 20s to lower 30s.
Friday will be the last day of near normal high
temperatures...before high pressure slides south from the north
ushering in cold air for the weekend. Saturday will remain
dry...before the next system moves into the region in the long term.

Long term...Saturday night through Thursday

Saturday night...the surface anticyclone is expected to move east
over the Ohio Valley by sunrise on Sunday...keeping cold and dry air
advection in place all night across Arkansas. The air mass that
becomes advected across Arkansas does look very cold and dry with
the consensus of model guidance indicating overnight lows in the
lower to middle 20s across the state with dew points forecast to fall
into the lower teens to single digits. This Arctic air mass is
expected to remain relatively shallow in nature...but complicates
the forecast with precipitation expected to return to the region as
early as Sunday morning.

Sunday...the GFS and European model (ecmwf) indicate that a strong shortwave trough
will dive south east from the northern plains and across the upper
Midwest Sunday morning. This trough is expected to remain north of
Arkansas...but it will result in some cyclogenesis across the
central and Southern Plains. Cyclogenesis to the west will result in
a quick response to warm air advection across Arkansas throughout
the day on Sunday. The warm air advection regime is expected to tie
into some rich Gulf moisture that forecast models indicate will
spread north across eastern Texas and Oklahoma on Sunday with dew
points creeping up towards 50 near Texarkana late Sunday afternoon.

The shallow Arctic airmass in place is expected to serve as a strong
lifting mechanism as warm and moist air impinges upon the shallow
Arctic air over Arkansas. The cold and dry air represents a steep
slope on low-level isentropic surfaces...enhancing the lift
associated with warm air advection over the region on Sunday. With
the differential positive vorticity advection aloft displaced to the
north...the lift over Arkansas is not expected to be overly deep on
Sunday...however the persistent warm air advection combined with an
increasing in middle-level frontogenetic forcing will lead to several
hours of persistent shallow low to middle level lift. The lack of
support aloft may keep the middle to upper troposphere dry...limiting
precipitation efficiency if the dendritic growth zone remains
unsaturated. Regardless...persistent low-level lift with strong
positive moisture advection over the shallow cold air mass should
result in widespread light rain/drizzle for much of the state on
Sunday.

Strong warm air advection will slowly modify the shallow cold air
mass from the southwest to northeast throughout the day on Sunday.
However think that the increase in cloud cover will filter out
enough insolation to prevent significant diabatic warming near the
surface throughout the day on Sunday. With this in mind...kept
temperatures quite cool on Sunday...with temperatures struggling to
climb above freezing Sunday afternoon. With the cold start to the
day on Sunday...there is a chance that precipitation will start out
as freezing rain late Sunday morning...with locations along and
south/southwest of Interstate 40 climbing above freezing by
Sunday afternoon. Locations to the north of Interstate 40
therefore have the greatest chance at seeing some minor ice
accumulations on Sunday with light precipitation throughout the
day. Will have to keep a close eye on Sunday as any heavier
precipitation with shallow cold air could really cause some
problems on area roadways. As it is now...only light ice
accumulations are expected...and primarily on elevated
surfaces/roadways.

Sunday night and Monday morning...the first shortwave trough is
expected to continue off to the northeast resulting in a secondary
surge of shallow cold air advection south across the upper Midwest
and approaching Arkansas late Sunday night/early Monday morning. In
its wake...a second strong shortwave trough is expected to move
southeast over Arkansas late Sunday night through early Monday
morning. This trough is expected to move over the state positively
tilted...but is expected to spread strong large scale forcing for
ascent over the area. The positive tilt to the upper trough will
probably reduce the chances for convection over Arkansas without
significant differential temperature advection...however it may help
to enhance frontogenetic forcing by sharpening up the baroclinic
zone/stationary cold front across the state.

To the north of this baroclinic zone...cold air advection may cause
ongoing precipitation to change over to snow. To the south...all
precipitation should be in liquid form. The position of the
boundary is obviously critical in terms of forecasting the
accumulation of any wintry precipitation Sunday night through
Monday morning. At this time the front is expected to remain near
or north of Interstate 40...so have some minor snow accumulations
in the forecast north of the Interstate. Exact snowfall amounts
and accumulation potential will vary greatly with the position of
the front...so left the forecast more or less broad brushed until
confidence increases in the exact position of the front. Will keep
a close eye on this forecast problem in later forecasts.

Monday through Tuesday...large scale forcing for subsidence will
spread over Arkansas from late Monday morning through late Monday
afternoon. This will cause precipitation to end quickly from west to
east during this time frame. Temperatures are also expected to warm
up quite a bit behind this system as the coldest air is scoured off
to the east resulting in warm air advection despite west and
northwest winds from the surface to 850 mb. Assuming temperatures
warm up as quickly as advertised from west to east on Monday... any
wintry accumulations should quickly melt Monday afternoon. Dry
conditions are expected to continue Monday night through Tuesday
morning.

High pressure returns for the end of the long term. A cold front
will move into the region late in period...but only bringing a
wind shift and an increase in cloud cover due to a lack of
moisture. Temperatures will begin a warming trend...with afternoon
highs in the upper 50s/lower 60s.

&&

Preliminary point temps/pops...
Batesville Arkansas 27 50 23 32 / 0 0 0 0
Camden Arkansas 33 60 32 44 / 0 0 0 0
Harrison Arkansas 31 50 18 35 / 0 0 0 0
Hot Springs Arkansas 31 60 30 42 / 0 0 0 0
Little Rock Arkansas 31 56 28 38 / 0 0 0 0
Monticello Arkansas 33 57 31 40 / 0 0 0 0
Mount Ida Arkansas 30 60 28 42 / 0 0 0 0
Mountain Home Arkansas 28 48 18 32 / 0 0 0 0
Newport Arkansas 28 49 23 32 / 0 0 0 0
Pine Bluff Arkansas 32 54 30 38 / 0 0 0 0
Russellville Arkansas 29 58 27 40 / 0 0 0 0
Searcy Arkansas 27 49 24 33 / 0 0 0 0
Stuttgart Arkansas 30 51 28 35 / 0 0 0 0
&&

Lzk watches/warnings/advisories...none.
&&

$$



Aviation...62

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