Area Forecast Discussion
Issued by NWS Little Rock, AR

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FXUS64 KLZK 210434

Area Forecast Discussion
National Weather Service Little Rock AR
1134 PM CDT Sat Apr 20 2019


Updated to include 06z aviation discussion.

Prevailing VFR conditions expected through the TAF period. Winds
will be light and variable overnight. By mid-day Sunday, southerly
winds will begin to increase with gust approaching 20 to 25 knots
across KHRO and KPBK, elsewhere gusts will be 10 to 15 knots. High
clouds will begin to move into the state tomorrow afternoon from
the west and northwest but will not affect ceilings.


.PREV DISCUSSION...(ISSUED 605 PM CDT Sat Apr 20 2019)

Updated to include 00z aviation discussion below.


VFR conditions expected through the period with light winds
overnight. By mid-morning Sunday, southerly winds will begin to
increase and will be the strongest at KHRO.

SHORT TERM...Tonight Through Monday

High pressure over the central plains continues pushing eastward
over the Natural State this afternoon, keeping west northwesterly
flow in place. The vigorous upper level low which brought stormy
weather to a large portion of the Southeast Region through the past
several days continues moving northeast through the Tennessee Valley
and Middle Atlantic Regions. This has kept winds slightly elevated
and gusty throughout the afternoon as stronger winds mix down due to
the strong pressure gradient resulting from the aforementioned storm
system. Otherwise, clear skies and plentiful sunshine have allowed
for a beautiful day across the forecast area, with temperatures
reaching into the upper 60s and 70s.

High pressure will begin to break down on Monday as an upper level
trough moves eastward through the Northern Plains, and another upper
level low digs southeastward through the Southwest. As these upper
level features approach, we could see cloud cover return/increase
late in the period. Otherwise, temperatures will continue to
gradually warm, with lows in the 40s and 50s, and highs in the upper
70s and lower 80s.

LONG TERM...Monday Night Through Saturday

As the period begins, shortwave upper ridging will slowly begin to
migrate from the south-central CONUS east as an expansive surface
ridge holds across the eastern third of the CONUS. Fair weather will
prevail early in the week with temps running several degrees above
average area-wide. By Tuesday morning, though, an approaching upper
trough invof the Desert Southwest will spur increasing southwest
flow aloft. Return flow on the western periphery of the
aforementioned surface ridge will help drive dewpoint temps into the
upper 50s to 60s F ahead of this system with model-delivered PWAT
values on the order of 1.5+ inches.

There are still several inconsistencies apparent in the 12Z suite of
guidance, although solutions from both models do appear to show
signs of converging today. Fairly confident this will be a
progressive, albeit slower-moving system, featuring widespread
soaking rainfall that will affect most if not all of the area. Based
on today`s guidance, confidence has increased with the overall
placement of the upper and surface cyclones across the Gulf states
and the likelihood a quasi-stationary front will extend
northeastward across portions of the state. This boundary will
demarcate the northern extent of the richest boundary layer moisture
and could help focus rainfall, especially given deep layer flow will
be oriented parallel to the boundary. Sufficient MLCAPE in the 500
to 1000 J/kg range will support thunder with heavy, convective rain
possible. Based on continued model uncertainty, especially run-to-
run inconsistencies, it is too early to determine what (if any)
larger-scale flood threat may exist with this system. It would not
be unreasonable to suggest at least isolated flooding could occur
across susceptible areas... namely southern and eastern portions of
the state. Temperatures will hover near average through the middle
of the period given the abundant cloud cover and rainfall.

The upper trough and associated surface features should exit by late
Thursday into Friday, although phasing issues with northern stream
troughing cast doubt on when precisely rain will end. Did trend
faster with removing the bulk of the rain in line with the ECMWF,
but left low-end PoP in the southeastern counties as a nod to the
GFS. Temperatures will quickly moderate through next weekend as
surface ridging builds in again.



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


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