Severe Thunderstorm Warning 452, NWS Norman, OK

Area Forecast Discussion
National Weather Service Norman OK
738 PM CDT Mon May 22 2017

...UPDATE...

&&

.DISCUSSION...
Made minor adjustment to precipitation probabilities, adjusting
upward for much of central Oklahoma based on trends. 00z KOUN
sounding revealed little instability and so ongoing strong/severe
convection across southwest Oklahoma should weaken before
impacting the I-35 corridor later this evening. Latest RAP
sounding has 1,000-1,500 J/kg of MLCAPE across southwest Oklahoma
and this is supporting a few intense cells with hail being the
main concern. One anti-cyclonic mesocyclone that persisted across
eastern Beckham County eastward toward Clinton produced golf ball
size hail on the south side of Elk City. Per Bunkers shear
vectors, left movers will most east-northeast at around 25 knots
and right movers will move southeast at aruond 30 knots. Storm
intensity and the severe threat should wane as storm intensity
decreases later this evening.

Otherwise only minor adjustments were made to other fields
including wind.

BRB

&&

.PREV DISCUSSION... /issued 730 PM CDT Mon May 22 2017/

DISCUSSION...

AVIATION... /For the 00z TAFs/
Latest regional radar mosaic shows showers moving across much of
central and northern Oklahoma impacting PNC/OKC/OUN, but moving
away from GAG/WWR. In the short term, the TAF sites with greatest
concern are CSM and HBR. Thunderstorms may impact these sites
through 02-03z and could even approach LAW. Once showers move east
of the area by late evening, VFR conditions are expected. We'll
need to monitor ceilings later tonight through tomorrow morning as
some locations could briefly see MVFR conditions but confidence
was too low for inclusion at this time.

BRB

PREV DISCUSSION... /issued 314 PM CDT Mon May 22 2017/

DISCUSSION...
The main concerns are rain/storm chances/potential tonight
into Tuesday.

Ongoing isolated to numerous light showers across central and
northern Oklahoma as of 3 pm should weaken in the next several
hours as isentropic lift around 700 mb weakens. This activity
will remain rather light. Some thunder may occur with this
activity, but do not think any strong or severe storms will
occur due to limited instability (MUCAPE mainly below 600 J/kg).

Severe thunderstorm potential now through tonight still appears
to be low with decreasing confidence. Cloud cover and rain have
limited instability in most locations north of a Mangum to
Seminole line. South of this line, some sun and daytime heating
have allow temperatures to rise into 70s. A few thunderstorms may
form near and this cloud shield line in the next several hours,
though this remains doubtful due to sufficient capping. Higher
chances for severe storms appear to occur over far eastern New
Mexico into west Texas late this afternoon where the air is more
unstable. This activity will continue to move east and southeast,
which may glance western north Texas and far southwestern Oklahoma
this evening if they can organize into a complex or two. If
severe storms occur, some severe hail and wind reports, mainly on
the lower end of severe spectrum (hail less than golf ball size
and winds under 70 mph), would be possible. No severe storms are
expected north of the line mentioned above due to limited
instability.

After midnight tonight into Tuesday morning, a cold front will
move south and through the area. A few lingering weak showers and
thunderstorms may occur across the area.

Tuesday afternoon, some clearing can be expected, though
temperatures will remain on the cool side for late May. Sufficient
daytime heating may allow for isolated to scattered showers and
weak thunderstorms to form in rather chilly unstable airmass. If
storms occur, no severe storms would be expected due to limited
instability (less than 500 J/kg), however small hail up to nickels
and gusty winds up to 50 mph could result.

Tuesday night through Thursday, dry weather is expected. Thursday
will be warmer (possibly much warmer) than Wednesday.

Friday through Memorial Day, a warm/hot humid airmass may evolve
across the southern Plains Friday through early Sunday, along for
some potential for severe thunderstorms/heavy rainfall. Most
models have been consistently depicting rather high amounts of
potential instability (MUCAPE 2000-5000 J/kg), high low level
moisture (surface dewpoints in the 60s to lower 70s), and
sufficient shear (0-6 km bulk shear 30-50 kt) for severe storms
with heavy rain late Friday through early Sunday. Capping may be
strong and limit storm development. For now, kept low chances for
storms across the area Friday night into Sunday. Have low
confidence in severe storm and heavy rainfall potential during
this time frame. Slightly cooler and drier conditions may occur
with the passage of a weak cold front Sunday into Memorial Day.

MBS

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  71  55  70  48 /  60  60  20  10
Hobart OK         70  53  70  47 /  80  60  20   0
Wichita Falls TX  73  59  72  51 /  30  50  40   0
Gage OK           66  50  68  43 /  60  30  20  10
Ponca City OK     73  53  69  47 /  40  60  20  10
Durant OK         75  58  70  51 /  20  40  40  10

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

12/14

Hazardous Weather Outlook...UPDATED
National Weather Service Norman OK
827 PM CDT Mon May 22 2017

OKZ004>048-050>052-TXZ083>090-240130-
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-
827 PM CDT Mon May 22 2017

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

.DAY ONE...Rest of This Evening and Tonight...

.THUNDERSTORMS...
There is a slight risk of severe thunderstorms across portions of
southwest Oklahoma and western north Texas. There is a marginal
risk of severe storms surrounding the slight risk area.

LOCATION...
The slight risk area is along and southwest of a line from Altus
to Lawton to Waurika. The marginal risk of severe storms is
southwest of a line from Mangum to Purcell to Ardmore Oklahoma.

TIMING...
Through 11 PM

IMPACTS...
Hail up to two inches in diameter is the main threat. Wind gusts
to 60 mph is a secondary threat.

DISCUSSION...
Instability and wind shear will remain high enough across
portions of southwest Oklahoma and western north Texas for strong
to severe thunderstorms through late this evening. Thunderstorms
are expected to decrease in intensity by late evening as
instability decreases.

.SPOTTER AND EMERGENCY MANAGEMENT STATEMENT...
Storm spotter groups and emergency management personnel across
western north Texas should monitor the forecasts and prepare for
the possibility of severe weather operations this evening.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday...

.THUNDERSTORMS...
Scattered thunderstorms will persist through the day Tuesday
before ending across the area. No severe storms are expected.

There is a chance of storms again Friday night through Sunday. If
storms do occur during this timeframe, severe weather and heavy
rainfall are possible.

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

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