Severe Thunderstorm Warning 663, NWS Norman, OK

Area Forecast Discussion
National Weather Service Norman OK
247 PM CDT Sun Aug 16 2020

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(This evening through Monday)
Issued at 247 PM CDT Sun Aug 16 2020

There are three ongoing mechanisms for convection across the area
this afternoon. Convection is ongoing and developing along and
north of an outflow boundary across central into northwest
Oklahoma. The radar mosaic suggests an MCV north of the outflow
boundary, which may explain why convection is occuring well behind
the outflow boundary (i.e., another source of ascent).

This outflow boundary is merging with a remnant (somewhat
diffuse) boundary across south central Oklahoma (especially on the
western flank of the old boundary where northeasterly winds are
gustier). Additional showers and thunderstorms are developing
along this remnant boundary across southeast Oklahoma. Finally,
upslope flow across the High Plains is resulting in convection in
the Texas panhandle. These areas of convection will continue
through the evening hours (with a slow south and eastward
progression).

While effective bulk shear is marginal, moderate to high
instability (MLCAPE ~4000-4500 J/kg) will favor pulse-type severe
thunderstorms that could produce marginally severe hail and
downbursts (i.e., damaging wind gusts) with the most intense
cores. If storms can coalesce and develop any substantial cold
pools, that would also increase the potential for damaging wind
gusts.

Mahale

&&

.LONG TERM...
(Monday night through next Saturday)
Issued at 247 PM CDT Sun Aug 16 2020

Through the extended forecast, a highly-amplified mid-level ridge
will remain across the western United States (centered near the
Four Corners region). As a result, the hottest temperatures will
remain to the west of the Southern Plains. Temperatures will be
slightly cooler/less hot and dew points slightly lower than recent
days.

Northerly flow aloft across the Southern Plains may result in
occasional complexes of thunderstorms to approach at least
Northern Oklahoma (around the eastern periphery of the ridge).
Therefore, low probabilities were included for many of the
overnight/early morning hours across northwest/northern Oklahoma.
The highest probabilities for convection would be when embedded
shortwave troughs approach from the north (enhancing the effective
bulk shear), but predictability/timing on these waves is
uncertain. Nevertheless, most of the period should be dry with
seasonable temperatures.

Mahale

&&

.AVIATION...
(18Z TAFS)
Issued at 1245 PM CDT Sun Aug 16 2020

Widely scattered thunderstorms across northern Oklahoma
continue to build slowly southward. Through 20-21Z WWR/OKC
appear to have the best opportunity of being impacted by
thunderstorms with MVFR conditions (mainly visibility). By mid
to late afternoon, other storms may develop along a surface
boundary in southern Oklahoma.  Models suggest most storms
will remain away from most TAF sites. This evening and overnight,
mainly VFR conditions are anticipated with a chance to slight
chance of storms.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  70  91  68  89 /  10  10   0   0
Hobart OK         69  94  68  93 /  20  10   0   0
Wichita Falls TX  71  93  71  94 /  30  20  10   0
Gage OK           66  92  64  92 /  30  10   0   0
Ponca City OK     67  91  66  88 /  10  10   0   0
Durant OK         72  94  71  95 /  30  10   0   0

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Heat Advisory until 7 PM CDT this evening for OKZ031-032-039>043-
     045>048-050>052.

TX...None.
&&

SHORT TERM...10
LONG TERM....10
AVIATION...06

Hazardous Weather Outlook...UPDATED
National Weather Service Norman OK
334 PM CDT Sun Aug 16 2020

OKZ004>048-050>052-TXZ083>090-172045-
Harper-Woods-Alfalfa-Grant-Kay-Ellis-Woodward-Major-Garfield-
Noble-Roger Mills-Dewey-Custer-Blaine-Kingfisher-Logan-Payne-
Beckham-Washita-Caddo-Canadian-Oklahoma-Lincoln-Grady-McClain-
Cleveland-Pottawatomie-Seminole-Hughes-Harmon-Greer-Kiowa-Jackson-
Tillman-Comanche-Stephens-Garvin-Murray-Pontotoc-Coal-Cotton-
Jefferson-Carter-Johnston-Atoka-Love-Marshall-Bryan-Hardeman-
Foard-Wilbarger-Wichita-Knox-Baylor-Archer-Clay-
334 PM CDT Sun Aug 16 2020

This hazardous weather outlook is for portions of northern...
western...central...and southern Oklahoma...and western north
Texas.

.DAY ONE...Through Tonight...

.Heat...
Heat index values of 105 to 110 are expected in southern Oklahoma
and western north Texas this afternoon.

.Thunderstorms...
There is a marginal risk of severe thunderstorms across most of
Oklahoma and all of north Texas through around 10 PM. In
Oklahoma, the marginal risk of severe storms is southwest of a
line from Medford to Guthrie to Holdenville. The strongest storms
will be capable of producing hail to the size of half dollars and
wind gusts of 60 mph. These thunderstorms will move south and
southeast.

.DAYS TWO THROUGH SEVEN...Monday through Saturday...

.Thunderstorms...
Scattered thunderstorms will continue over western and
southwestern Oklahoma, and north Texas into Monday morning. A few
strong storms will be possible.

Low thunderstorm chances return to northwestern and western
Oklahoma late Tuesday night through early Wednesday morning, and
again late Thursday night through early Friday morning.

Get graphics and more details at weather.gov/norman...and follow
our weather forecast office on Twitter and Facebook.

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