Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 202314
AFDTSA

Area Forecast Discussion
National Weather Service Tulsa OK
614 PM CDT Fri Oct 20 2017

.AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
VFR elements to prevail for the first portion of the TAF period.
WS to ensue at all sites from 03z through mid morning. MVFR cigs
to develop overnight ahead of the next system that will impact the
NE sites just beyond this TAF issuance. Cigs should rise some by
afternoon with strong mixing in place...however MVFR cigs are
expected to prevail at all sites for the last half of the period.
Strong southerly sfc winds again tomorrow...with gusts between
20-25 kts at most sites except KFSM.



&&

.PREV DISCUSSION... /Issued 250 PM CDT Fri Oct 20 2017/

DISCUSSION...
Main forecast concerns are the severe thunderstorm and heavy rain
potential, especially across eastern Oklahoma, tomorrow evening
and into early Sunday morning.

Early this afternoon, a few light showers continue across portions
of western Arkansas, in association with a fast moving disturbance
ahead of the main upper level wave currently located over the
western United States. Additional activity could develop later
tonight and into tomorrow morning as low level moisture continues
to increase across the region, along with the developing low
level jet. Steepening mid level lapse rates will provide an
isolated thunderstorm threat tonight. The low chance of showers
and thunderstorms will continue through most of the daylight hours
tomorrow.

Tomorrow afternoon, thunderstorms will develop along the
approaching cold front across parts of Kansas, southwestward into
western and central Oklahoma. The expected line of thunderstorms
may sneak into portions of northeast Oklahoma by early evening,
but most of the region will be affected toward mid to late evening
and into early Sunday morning. CAPE values ahead of the front
should be in the 2000-3000 J/kg range. Deep layer shear will be
sufficient for severe hail, especially with early, more isolated
development, but conditions remain more favorable for damaging
winds associated with more linear structures. While leading edge
QLCS tornado potential will be nonzero, forecast low level shear
parameters do not seem overly supportive of a large threat.
Overall, the severe thunderstorm threat should maximize across
portions of Oklahoma and diminish some once the line moves into
Arkansas.

Locally heavy rainfall will also be a concern, with storm totals
averaging between 1 and 2 inches and isolated amounts possibly
approaching the 3 to 4 inch range. Widespread flash flooding does
not look likely at this point, but rainfall amounts of this
magnitude could lead to an increased potential in a few locations.

Some showers and thunderstorms may linger across parts of far
eastern Oklahoma and western Arkansas into Sunday before the upper
trough and cold front finally clear the area later in the day.
A secondary cold front will move through the area late Monday and
into Tuesday, with no precipitation chances associated with it.

A stronger push of cold air is looking more likely toward the end
of the next work week and into next weekend. Some moisture
recovery may occur ahead of this system to produce a few showers
ahead of it on Friday. The bigger story, however, is the
potential for sub-freezing temperatures for portions of the area
into next weekend. We may be looking at Frost/Freeze Headlines at
this same time next week.

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&

$$

SHORT TERM...99
LONG TERM....99
AVIATION...23


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