Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 252337 AAA
AFDLZK

Area Forecast Discussion...Update for Aviation
National Weather Service Little Rock AR
535 PM CST Sat Feb 25 2017

.Aviation...

Overall VFR flight conditions will be seen in the next 24 hours.
Winds will be light from the northwest to north, become light and
variable later this evening and overnight. Winds on Sunday will be
southeast at 5 to 15 mph. (59)

&&

.Prev Discussion.../ Issued 248 PM CST Sat Feb 25 2017/
.Short term...Tonight through Sunday night.

High pressure remains centered along the Red River at this time.
Light northerly flow around this feature has kept temperatures in
check with readings generally in the mid 40s to lower 50s which is
actually below normal for one of the few times of late.

The high will move overhead tonight and with clear skies and little
winds, temperatures will drop below freezing across a good part of
the state. Will continue the thinking of the previous shift and just
issue a special weather statement to highlight this. The thinking
remains that we are so far removed from our climatological normals
for the final freeze and we are still likely to see several more
nights of below freezing temperatures before the end of the season.

The high will be located over the Tennessee Valley by morning with
light southerly flow already returning on its backside. Moisture
will be increasing during the day with precipitation chances on the
increase as the day progresses. Precipitation chances will ramp up
considerably Sunday night as a fast moving shortwave trough passes
overhead. Strong overrunning and warm air advection pattern with an
approaching warm front will result in widespread showers. Pattern
not overlay favorable for thunderstorms but some elevated convection
is possible for isolated storms.
&&

.Long term...Monday through Saturday

A fast moving shortwave trough will continue moving off to the
northeast of Arkansas Monday morning. The large scale forcing for
ascent associated with this upper trough combined with a strong
low- level warm air advection pattern will result in numerous
showers with isolated thunderstorms across Arkansas from Sunday
night into Monday morning. As the shortwave trough moves
northeast, the coverage of showers and storms is expected to
decrease Monday morning. Upstream, a large upper trough is
expected to move south over southern California on Monday, causing
the jet stream to move north and tilt away from zonal flow aloft
towards southwest flow aloft over the central conus. This should
result in an acceleration of the warm air advection pattern
bringing a warm front north from the ARKLATEX area towards central
Arkansas late Monday afternoon and evening. The strength of the
warm air advection pattern will play a large role in thunderstorm
chances and their potential impact on Arkansas Monday afternoon
and evening.

The GFS and ECMWF continue to show a moderate warm air advection
pattern on Monday favoring a later return of the warm front moving
north across the state. Both models indicate the warm front moving
north after sunset Monday, limiting the opportunity for
thunderstorms that develop near the warm front from becoming well
organized and severe.

The 12z NAM today advertised an aggressive warm air advection
pattern causing the warm front to lift north from near the Louisiana
border towards central Arkansas from 21z to 00z. The faster motion
of the warm front brings the warm front north when its warmer than
the GFS and ECMWF solution indicate. This results in the NAM
advertising over 2000 j/kg of MLCAPE along the warm front where deep
layer bulk shear is expected to be around 50 kts. The thermodynamic
and kinematic environment certainly supports the possibility for
supercell thunderstorms in this environment, but a strong lifting
mechanism is the primary missing ingredient. If a thunderstorm was
able to initiate near the warm front, it would certainly pose a
threat for damaging winds and very large hail. If the storm were to
become organized and cross over the warm front, it could pose a
tornado threat as well.

At this time, upped our chances for storms a bit Monday afternoon to
account for the possibility for some strong storms near the warm
front Monday afternoon and evening. The severe weather threat is
limited by a lack of strong lift, and by the potential that the warm
front simply doesn`t move north fast enough to allow for instability
as high as the NAM is advertising today. We will advertise at least
a low chance for severe storms Monday afternoon and evening,
primarily focused on southern Arkansas. Will closely watch the
timing of the warm front as we get closer to Monday to determine if
the risk for severe storms increases or decreases.

Tuesday, the NAM/GFS/ECMWF all indicate that the "warm sector" will
be in place across Arkansas by Tuesday afternoon. The consensus of
guidance is that MLCAPE values will climb to 1000 to 1500 j/kg with
deep layer bulk shear increasing to 50-60 kts over the state. This
will result in a more widespread threat for severe storms across
Arkansas Tuesday afternoon. However, similar to Monday afternoon`s
limitation, there is a lack of strong lift to cause storms to
develop in the first place. The thermodynamic and kinematic
parameters support a threat for severe storms if anything is able to
develop across Arkansas Tuesday afternoon, but it is possible that
storms hold off until the southern California upper trough arrives
Tuesday night into Wednesday morning.

Tuesday night - Wednesday, the southern California upper trough is
expected to send strong large scale forcing for ascent over Arkansas
starting around midnight Tuesday night. There will still be some
threat for severe storms as the strongest lift arrives Tuesday
night, however with several hours to cool off/stabilize the lower
atmosphere, the severe weather threat is expected to be dampened.
Large hail and damaging winds would be the primary threats with any
severe storms during this time. A broken line of thunderstorms is
expected to develop along a cold front Wednesday morning, and
accompany the front southeast across the state through early
Wednesday afternoon. Rain chances will decrease Wednesday afternoon
from northwest to southeast as drier air filters into the region
behind the front.

Wednesday night through Saturday, another cool and dry air mass will
build across Arkansas behind Wednesday`s front. Temperatures may
fall to freezing again Wednesday night across north and northwestern
Arkansas as skies clear out. With upper level high pressure in place
for the remainder of the week, a cool and dry air mass is expected
through the end of the week. Temperatures will be closer to seasonal
normals, and rain chances will be very low through the end of the
week.
&&

.PRELIMINARY POINT TEMPS/POPS...
Batesville AR     29  55  42  61 /   0  20  70  30
Camden AR         30  64  50  73 /   0  10  70  50
Harrison AR       28  53  38  62 /   0  20  40  30
Hot Springs AR    30  58  45  65 /   0  20  70  50
Little Rock   AR  30  59  45  66 /   0  10  70  40
Monticello AR     32  63  52  71 /   0  10  60  50
Mount Ida AR      28  58  44  65 /   0  20  70  40
Mountain Home AR  27  54  38  61 /   0  20  50  30
Newport AR        29  55  42  61 /   0  20  70  40
Pine Bluff AR     31  61  48  67 /   0  10  70  50
Russellville AR   28  57  43  64 /   0  20  60  30
Searcy AR         27  57  42  64 /   0  10  70  30
Stuttgart AR      31  59  46  65 /   0  10  70  40
&&

.LZK Watches/Warnings/Advisories...NONE.
&&

$$

56/Cavanaugh



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