Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 131524
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
1024 AM CDT Sun Aug 13 2017

.UPDATE...
Recent satellite and radar observations indicate one convectively
induced mid level vorticity maximum just east of Fort Smith, with
another just north of Shreveport. Precipitation continues to be
promoted, as the features move to the east. Near term
precipitation forecasts take into account expected movement of
these systems.

55

&&

.PREV DISCUSSION...(ISSUED 640 AM CDT Sun Aug 13 2017)

AVIATION...

Overall VFR flight conditions are forecast, with some ceilings,
while patchy MVFR conditions with rain and showers. Light to
moderate rain and showers, with very spotty thunder, is moving into
western AR and will gradually move east. The convection will affect
all Tafs sites. Isolated thunderstorms may also be seen, especially
over central to southern areas, and MVFR conditions are expected
with the heavier convection. Winds will be northeast to southeast at
3 to 10 mph. (59)

Prev Discussion.../ Issued 331 AM CDT Sun Aug 13 2017/

Main concerns in this forecast cycle are chances of convection
each day, any severe storm threat and the potential for heavy rain
and possible flooding or flash flooding. Temperature forecast will
remain below normal levels.

Currently light to moderate convection is moving east into AR from
the west, with the greatest over southwest AR. Embedded thunder
is seen in some of the complexes. At this time, strong to severe
storm threat is very low. The convection is associated mainly with
upper short wave energy moving through the mean upper west to
northwest flow. This upper system will keep good to likely chances
of rain over AR today. At the surface, dew point temperatures
were in the 60s with a few 70s, while temperatures were from the
mid 60s to mid 70s. Weak surface ridging was to the northeast of
AR, with a northeast to east wind flow into AR. A weak frontal
boundary was also over northern LA to north TX.

SHORT TERM...Today Through Monday Night

The forecast will start with high POPs due to in place and upper
level energy moving into AR. One main area over the north and
another over the south. This will progress eastward through the
day and forecast transitions the higher POPs from the southwest to
south central. Some heavy rain is expected with localized
flooding. Models gradually move this system east-southeast through
AR today to evening, with a gradual lowering of POPs over the
north, while staying high over the south. Tonight, a gradually
lower of overall POPs over AR as this system moves east of AR,
with the main focus over southern AR. On Monday, the weak frontal
boundary over northern LA lifts more northward into AR, while a
bit less upper short wave energy is seen in model runs, overall
POPs will be good on Monday with some interaction. Monday night,
models have the weak frontal boundary even farther north, while a
lower amount of upper lift moving through the region, an overall
lower of POPs will be seen. Again, the threat of any strong to
severe storms will be low to isolated. Due to the repeated periods
of rain, localized flooding will be possible. Flash flooding will
also have to be monitored. Temperatures will be cooler than
normal due to the clouds and rain.

LONG TERM...Tuesday Through Saturday

The period will start with some rainfall across a better part of the
state as a thunderstorm complex, or the remnants thereof, will be
centered over Arkansas. Have some 40-60 percent rain chances in the
forecast to account for this, with the highest values generally in
the northern half of the state. For Tuesday night onward, an upper
trough will shift into the southern Rockies while ridging moves
overhead. This will produce a more seasonal return flow pattern over
the mid south, pushing temperatures back up to seasonal norms and
lowering rain chances in general. Tuesday may still be below normal
depending on how much rain and cloud cover are present though, but
expect widespread highs in the low 90s for Wednesday and beyond.

While rain chances will be lower after Tuesday, the ridge aloft will
be what we lovingly refer to as a "dirty ridge." That is, with
sufficient low level moisture in place and lack of a high amplitude
or exceptionally strong upper ridge, diurnally driven isolated to
scattered storms will be possible most every afternoon and evening
from Wednesday onward. Such a pattern will favor the northern or
northwestern half of the state for afternoon convection as
disturbances in the upper flow move around the periphery of the
ridge, which should be to the south or southwest of Arkansas.

By the end of the week, the upper ridge will begin to contract or
shift towards the southwest as the upper flow across the continental
US becomes zonal in nature. This should allow a cold front to
approach the region from the northwest, with the chances for showers
and thunderstorms increasing.

&&

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

$$


Aviation...99



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