Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 210509 AAA

Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
1109 PM CST Fri Jan 20 2017

Expect VFR conditions to persist into the overnight hrs...but this
will change near sunrise as moisture levels increase. This will
result into some FG and DZ across some SRN sites. Rain chances will
then return by the afternoon hrs...with some TSRA also possible.
These increased precip chances will persist into Sat evening.

.PREV DISCUSSION...(ISSUED 325 PM CST Fri Jan 20 2017)

SHORT TERM...Today Through Sunday

In the near term, forecast is right on track as low and mid level
clouds have diminished greatly over the CWA. Some high cloud
cover, associated with the upper jet, will persist- preventing
maximum insolation. That said, temperatures will still rise to the
60s and 70s during the day Friday... nearing 20 degrees above
average, but still a few degrees below record values.

A variety of convective weather is possible Saturday night into
Sunday as an upper wave pattern amplifies and a strong, deepening
low approaches the state. Convective initiation will begin around 00z
Saturday as an impulse ejects out ahead of the main low. Upscale
growth of the convection should be healthy under strong mid/upper
level diffluence. Models have trended warmer and moister with the
low level environment, however, GFS is still persistent with a
low level stable layer across the northern portions of the CWA. As
such, convection may be elevated initially before quickly becoming
surface based.

With the deep low moving close to the state, fairly cold air in
the mid levels will result in some fairly steep mid-level lapse
rates between 6.5 and 8 C/km. With freezing levels between 700 and
800mb, hail is the main threat with this system. Limited
streamwise vorticity at the surface, with a marginally unstable
near-surface layer- both the threat for wind and tornadoes is low,
but not non- existent. The greatest threat would be further to the
southeast and along the surface boundary, where low level helicity
may be enhanced.

By Sunday morning, the deep low will be located almost directly
over the state. Even after the surface cold front moves through
the region, convection may follow as a result of continued steep
mid- level lapse rates. As such, the threat for hail may continue
a bit into Sunday morning and early afternoon, before cooler/drier
low/mid level air filters into the region.

LONG TERM...Sunday Night Through Friday

Extended models are in decent enough agreement initially but begin
to diverge as the period lags on. Biggest differences arise with the
placement of a large H5 trough by midweek with the GFS giving it
more of a negative tilt and places it further west versus the ECMWF.
That being said, will take a middle of the road approach as overall
the period looks to be fairly quiet.

Period initiates with the system that will be bringing the wet
weather to the area over the weekend pulling out. The parent low
will be over the SE Conus with the trailing cold front located over
the SE part of the state for a chance of precipitation in the
evening hours.

In its wake, NW flow aloft will develop with temperatures close to
normal. The pattern will remain progressive in nature as the
aforementioned trough digs into the western Conus and upper ridging
builds over the area with temperatures back in the 60s.

A fast moving boundary will bring a slight chance of showers to
mainly the east early Wednesday with the upper flow buckling in its
wake. Seasonably cool air and dry conditions will return to the
area for the remainder of the period.


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


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