Severe Thunderstorm Warning 798, NWS Norman, OK

Area Forecast Discussion
National Weather Service Norman OK
1231 PM CDT SAT SEP 17 2016

.DISCUSSION...
Aviation discussion for the 18 UTC TAFs is below.

&&

.AVIATION...
Overall, VFR conditions are expected to continue. The timing and
locations of TSRA remain very uncertain.

MVFR conditions near KWWR and KGAG are expected to become VFR by
20 UTC.

ISO-SCT SHRA/TSRA will likely affect western and central Oklahoma
with timing generally 19-03 UTC. A line/complex of storms are
forecast to impact all TAF sites for a 1-3 hour period 02-09 UTC.
Variable gusty winds, hail, and brief IFR or lower conditions are
expected with any TSRA.

Patches of IFR or lower conditions may form after TSRA generally
after 06 UTC. Did not mention due to low confidence of occurrence.

MBS

&&

.PREV DISCUSSION... /issued 1130 AM CDT SAT SEP 17 2016/

UPDATE...
Some uncertainty as to how/when showers/storms will affect the
area this afternoon and tonight, mainly due to the line of storms
moving east across the Panhandles and the scattered activity
ongoing in West TX. If this activity maintains itself, especially
the line of storms, into the fa then showers/storms could be
affecting parts of the area earlier than previously forecasted.
Otherwise, isolated/scattered showers/storms will be possible
across portions of Western OK/W N TX later this afternoon and
evening. While that is going on, an MCS could develop and then
move into and across portions of the fa later this evening and
overnight. Unfortunately many of the models don't have a great
handle on the current activity and in some cases not really
showing it at all so confidence on how things will play out is
low.

What can agree on is that some of the storms could be strong to
severe with large hail and strong winds. Heavy rain will also be a
concern through early Sunday.

Made some adjustments to grids to show current thoughts but some
updates will likely be needed as the day progresses and hopefully
the situation becomes more clear. All updates out soon.

PREV DISCUSSION... /issued 647 AM CDT SAT SEP 17 2016/

AVIATION...
17/12Z TAFs. LIFR conditions will be seen across northern and
western Oklahoma terminals through at least 14-15Z with gradual
improvement through 17-18Z. VFR conditions expected thereafter
before TSRA expected to affect region, first across northwest and
western Oklahoma terminals toward and after 03Z, and spread
eastward over rest of terminals toward and after 06Z. Isolated
nature of TSRA this morning and afternoon will preclude mentioning
in terminals.

PREV DISCUSSION... /issued 412 AM CDT SAT SEP 17 2016/

DISCUSSION...
Potential for dense fog advisory for northern and central portions
of Oklahoma being complicated by stratus development and effects
from ongoing convection. Right now it appears that most of the dense
fog will be confined to areas near and north of the Oklahoma-Kansas
border and also over northeast portions of Oklahoma. We will be
monitoring need for advisory just south and east of stratus deck
that covers the northwest third-or-so of Oklahoma.

Forecast next 24-36 hours still remains a challenge with overall
weak forcing and diffuse boundaries remaining over and near the
region. Scattered storms over far northern Oklahoma near diffuse
surface front and region of weak warm advection forecast to continue
through sunrise but weaken as it progresses slowly east and
southeast. Convection out near Lubbock forecast to shift slowly east
into western north Texas region through the morning hours. Main
model of choice is the Texas Tech WRF which has the best handle on
current convective trends. This particular model also much less
aggressive with late morning and afternoon convection near broad area
of lower level convergence associated with mentioned front. However,
with enough signal in other models, we will keep low pops going
through the day for isolated/scattered convective potential. Much
more widespread rain activity progd to move into western portions of
Oklahoma this evening and progress east and southeast over much of
the region overnight and Sunday morning. Operational NAM and Texas
Tech WRF slightly farther north than most other models and will be
considered with higher pops into central and north central Oklahoma
than model initializations yield. As far as severe weather is
concerned, any storm that develops this afternoon and/or affects the
region through the evening hours will exist in an environment with
enough shear and instability to yield severe weather potential.
Toward and after midnight, the impacts will be primarily strong wind
gusts and heavy rain.

After the anticipated MCS tonight and Sunday morning, primarily dry
forecast with above average temperatures and humid conditions most
of next week. Rain chances return mainly to western and northern
portions of Oklahoma by late week.

&&

.OUN Watches/Warnings/Advisories...
OK...None.
TX...None.
&&

25/17

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