Area Forecast Discussion
Issued by NWS Little Rock, AR

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144
FXUS64 KLZK 210532
AFDLZK

Area Forecast Discussion
National Weather Service Little Rock AR
1132 PM CST Sat Jan 20 2018

.AVIATION...
Overall VFR and patchy MVFR ceilings will start the forecast.
Ceilings are expected to slowly lower Saturday night to Sunday
morning, with patchy IFR possible around Sunday sunrise. Patchy
drizzle or light rain may be seen in areas, as well as fog forming
in many areas. Winds will be south at 5 to 15 mph, with some higher
gusts over northwest AR. A low level jet will set up and create
areas of low level wind shear at all Tafs from the south. Winds on
Sunday will become elevated from the south at 10 to 20 mph. On
Sunday in the afternoon to evening, convection will develop and
affect all TAF sites as a system moves through the region.

&&

.PREV DISCUSSION...(ISSUED 830 PM CST Sat Jan 20 2018)
Discussion...

Overall forecast on track. Warm front has lifted north of AR, with a
warm and moist flow from the south into the state. Temperatures were
around 50 to the lower 50s north, mid to upper 50s central, and
around 60 over southern AR. Overcast skies were seen over most of
the region, some patchy fog and drizzle or sprinkles being noted in
spots. Saturday night, overcast skies will be seen in most
locations, with patchy fog, drizzle or even some light rain at
times. Lows will be mostly in the 50s. Sunday will see the chance of
convection pickup later in the day ahead of a surface front and
upper system. SPC day 2 continues to marginal risk of strong to
severe storms over western AR, then moving east, while current
models show weakening trends. (59)

Prev Discussion.../ Issued 550 PM CST Sat Jan 20 2018/
Aviation...

Overall VFR and patchy MVFR ceilings will start the forecast.
Ceilings are expected to slowly lower Saturday night to Sunday
morning, with patchy IFR possible around Sunday sunrise. Patchy
drizzle or light rain may be seen in areas, as well as fog forming
in many areas. Winds will be south at 5 to 15 mph, with some higher
gusts over northwest AR. A low level jet will set up and create
areas of low level wind shear at all Tafs from the south. Winds on
Sunday will become elevated from the south at 10 to 20 mph. On
Sunday in the afternoon to evening, convection will develop and
affect all Taf sites as a system moves through the region. (59)

Prev Discussion.../ Issued 241 PM CST Sat Jan 20 2018/
SHORT TERM...Tonight Through Monday

Moisture levels have increased significantly across at least portions
of the area early this Sat afternoon as a warm front is lifting
north over the state. Dewpts over SW AR have increased into the
50s...while north of the warm front dewpts remain in the 40s across
NE AR. Some scattered SHRA and patchy DZ have also be noted with
this moisture surge. Expect continued chances for patchy DZ and
spotty SHRA through the rest of the afternoon and into the overnight
period...with a mostly cloudy expected. Some patchy fog may also be
seen.

Breezy SRLY winds will be seen for Sun afternoon and evening as the
pressure gradient tightens with the strengthening SFC low to the
west of AR. An upper level shortwave trough will exit the Rockies
Sun afternoon...and lift ENE into NE KS by late Sun night. SFC low
pressure will continue to strengthen as this happens...with a
trailing cold front surging east through the state Sun night into
early Mon morning. Expect scattered to numerous SHRA and TSRA to
develop along a prefrontal SFC trough over ERN OK late Sun afternoon
into early Sun evening...with convection becoming more widespread
Sun night as this activity shifts east into central sections of the
state just before midnight Mon morning.

At this time...there looks to be some potential for a few strong to
possibly SVR storms Sun evening into early Mon morning across at
least some portion of the CWA. Forecast SRH values look quite
impressive Sun evening...with forecast 0-1km SRH over 400 m2/s2 just
ahead of the convection. Forecast instability looks to be the
limiting factor in the overall threat for SVR storms as there
remains limited forecast instability for SFC based convection. This
may change however...so will have to pay close attention to the
instability as the storm system approaches Sun afternoon.

Even with the uncertainty regarding instability...do think there
could be some damaging winds with the strongest storms. Given the
forecast low level SRH values...rotating updrafts will also be
possible...resulting in some potential for weak...brief tornadoes
along the leading edge of the convection. The convection will be
fairly quick moving to where the heavy rain threat will be
limited...with just some locally heavy rainfall possible. The threat
for hail will also be limited given the lack of CAPE in the hail
growth zone.

Expect drier and more stable air to move into the state for
Mon...though some breezy W and NW winds will remain possible through
Mon afternoon.

LONG TERM...Monday Night Through Saturday

No significant changes were made to the current fcst thru the PD. A
weak CDFNT wl bring a reinforcing shot of cooler Pacific air into
the region on Tuesday. Sfc high pressure will prevail thereafter
through the mid week period. Look for a slow moderating trend later
next week as the sfc high shifts Ewd and S/SELY winds return.

Clouds/low lvl moisture wl start to increase over AR on Friday ahead
of a new storm system forming over the Rockies. Rain chances wl
return to the FA Fri night and Sat as the assocd CDFNT apchs fm the
Plains States. The front itself is currently fcst to enter Wrn AR on
Sat. Current model data suggest minimal potential for any strong
convection, due to lack of instability and an elongated, positively
tilted, upr trof.

&&

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

$$


Aviation...51



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