Area Forecast Discussion
Issued by NWS Little Rock, AR

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848
FXUS64 KLZK 271216 AAA
AFDLZK

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
616 AM CST Mon Feb 27 2017

.DISCUSSION...

Updated for the 12z aviation discussion below.

&&

.AVIATION...

Between a saturated low level air mass, and showers and
thunderstorms, flight categories will be a mess today. Generally
speaking, expect mainly low-end MVFR ceilings to prevail through
the period. Visibility should remain mostly above 6SM except
within convection. Expect -SHRA or possibly some -TSRA to be
nearby central and southern terminals through through 17-18z, with
a lull afterwards lasting through the evening hours. Another round
of scattered SHRA with ocasional embedded TSRA is expected across
the southern half of the state tonight. Have tried to account for
this with TEMPO groups after 00z.

&&

.PREV DISCUSSION...(ISSUED 349 AM CST Mon Feb 27 2017 )

SHORT TERM...Today Through Tuesday Night

A stationary boundary is situated from northeast Texas across the
Arkansas/Louisiana border and into northern Missippi this morning. Showers
with embedded isolated thunder continue along this boundary this
morning, supported by a 100kt subtropical jet and low amplitude
shortwave trough over the region. This trough will be east of
Arkansas by shortly after daybreak and convective activity will
wane as the morning wears on. Another weak disturbance will move
over the state late this afternoon and evening and may kick off a
few more showers over the forecast this evening and into the first
part of the overnight hours. Confidence is not terribly high with
this time frame though so only have 20-30 percent rain chances
tonight.

The biggest concern in the short term is Tuesday and the potential
for severe storms. A deep western trough will begin to shift east
from the Sierras late tonight, exiting the Rockies by Tuesday
afternoon. Ahead of this trough, the aforementioned stationary
front will have shifted north as a warm front through Arkansas,
placing us squarely in the warm sector of the developing storm
system. From an ingredients standpoint, the recipe for severe
storms looks to be in good shape. Surface based instability across
a large portion of the forecast area will be upwards of 1,000
J/Kg Tuesday afternoon and evening. Speed shear will be more than
sufficient for organzized severe storms, with bulk shear upwards
of 50-60kt across the entire state and 0-1 and 0-3 helicity values
more than sufficient for supercells and even tornadoes. The
question is whether convection will fire in the warm sector
Tuesday afternoon and evening, or whether it will be primarily
along/ahead of the cold front that enters the state Tuesday night.
At this point, it appears there is a strong chance for at least a
few storms Tuesday afternoon and evening, before evolving into a
linear convective mode Tuesday evening into the overnight period
as the cold front accelerates into Arkansas. The best chances for
severe storms will likely be across the northern part of the
state, coincident with the best shear/instability/lapse rates.
This is where SPC has continued to advertise an Enhanced Risk
area in the convective outlook.

While there is still some uncertainty regarding how this event
will evolve, the overall setup is supportive of very strong
storms. At this point I would encourage individuals to continue to
closely monitor this forecast.

LONG TERM...Wednesday Through Sunday

Frontal boundary will be moving out of eastern Arkansas during the
morning hours Wednesday, with showers/storms coming to an end. High
pressure will follow the front, with temperatures much closer to
seasonal averages.

By the end of the week, the high will move east, with return flow
setting up. Aforementioned front will back to the north over the
weekend, with showers/storms developing by Sunday.

&&

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

$$


Aviation...64



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