Special Weather Statement, NWS Tulsa, OK

Area Forecast Discussion
National Weather Service Tulsa OK
1236 PM CDT Thu May 27 2021

.DISCUSSION...

The 18Z TAF forecast discussion follows...

&&

.AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
Scattered storms, eventually transitioning into a storm complex,
will sweep across the TAF sites thru 04Z this evening. A mix of
MVFR and VFR cigs will see tempo IFR conditions in heavy rain
producing storms with gusty winds possible. Eventually a cold
front will bring a wind shift to the north by early Friday with
periodic MVFR/IFR cigs possible. A return to VFR cigs is possible
toward the very end of the forecast period across E OK.

Lacy

&&

.PREV DISCUSSION... /Issued 1124 AM CDT Thu May 27 2021/

DISCUSSION...

Forecast has been updated this morning based on the latest trends
in the data. Model soundings this morning were weakening the cap
fairly quickly today, likely due to ascent from warm
advection/isentropic lift evident on 305K surface. 12Z OUN
sounding showed very steep mid level lapse rates and large CAPE,
with decent deep layer shear. Low level shear is still fairly
weak. Storms are already ongoing across NE OK, evidence of
weakening cap. More storms to develop later today as daytime
heating continues, even with quite a bit of cloud cover, as very
rich low level moisture is in place with low 70s dewpoints. Very
large hail and damaging winds main threats. Tornado potential
should be localized and focused along outflow boundaries, though
given the time of year and the environment, the potential does
exist for a strong tornado. Storms eventually congeal into an MCS
and plow southeast with wider swaths of damaging wind potential
becoming main threat. A QLCS tornado threat will exist on any
bowing structures that surge to the east to northeast. With
multiple rounds of storms possible along and north of I40 thru
tonight, a flash flood watch has been issued.

Lacy

PREV DISCUSSION... /Issued 548 AM CDT Thu May 27 2021/

.UPDATE...

AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.

Convective forecast is slightly clearer than with the last TAF
set, with most data settling in on the late afternoon/evening
development moving from north to south across the area. Will keep
the idea from the 06Z TAFs, outlining a TEMPO group window
featuring near severe wind gusts and IFR conditions within a
larger prevailing group with a VCTS mention. Recent data do,
however, continue to show isolated to scattered early afternoon
development and will slightly widen the time window for the VCTS
mention as a result. MVFR conditions and a shift to more north to
northwesterly winds will occur in the wake of the complex,
although VFR conditions should begin to return to the NE OK
terminals late in the period.

PREV DISCUSSION... /Issued 323 AM CDT Thu May 27 2021/

DISCUSSION...
Certainly not a clear cut situation today, as ongoing storms to
our north, convective outflow boundary(s), and a potential
convectively induced MCV over southwest OK muddle the early day
convective chances. The more recent HRRR runs maintain some weak
convection across parts of northeast OK this morning, with some
strengthening possible later this morning as storms move into
parts of northwest AR.

Assuming that the morning convection isn't too disruptive, expect
an extremely unstable (SBCAPES 3500-4000 J/KG) and uncapped
atmosphere south of a frontal boundary draped across southeast KS
into northwest OK this afternoon. Convection will likely develop
by early afternoon along the boundary in KS, with some discrete
storm development into parts of northeast OK by mid-afternoon. The
forecast instability and increasing bulk shear will support
supercells with the initial activity, with very large hail,
damaging winds and a few tornadoes possible. Storms will likely
develop into one or more clusters by late afternoon, and then
propagate south/southeast through the forecast area during the
evening/overnight hours. The primary threat during this time will
be damaging winds, with at least a low chance of leading edge
tornadoes. The MCS is expected to push south of the forecast area
late tonight.

May have some scattered showers/storms across southeast OK on
Friday, near and to the north of the frontal boundary across
northern TX. Otherwise, cooler and drier conditions are expected
through the weekend as surface high pressure builds into OK/AR.
May see some morning lows in the 40s both Saturday and Sunday
mornings across parts of far northeast OK and northwest AR, with
highs in the 70s areawide.

The western U.S. upper trof will slowly slide into the Plains by
early next week, with rain chances returning and lingering for
much of the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
TUL   82  59  73  53 /  90  90  10  10
FSM   87  67  80  56 /  50 100  10  10
MLC   84  63  76  56 /  30 100  20  20
BVO   81  55  72  49 /  90  60   0   0
FYV   81  59  74  48 /  80 100  10   0
BYV   81  59  72  48 /  80 100  10   0
MKO   83  61  73  53 /  70 100  10  10
MIO   80  56  70  48 /  90  90   0   0
F10   82  61  73  53 /  70 100  10  10
HHW   84  67  80  60 /  10  90  30  20

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...Flash Flood Watch through late tonight for OKZ054>072.

AR...Flash Flood Watch through late tonight for ARZ001-002-010-011-
     019-020.

&&

AVIATION.....30

Hazardous Weather Outlook
National Weather Service Tulsa OK
453 AM CDT Thu May 27 2021

ARZ001-002-010-011-019-020-029-OKZ049-053>076-281000-
Adair OK-Benton AR-Carroll AR-Cherokee OK-Choctaw OK-Craig OK-
Crawford AR-Creek OK-Delaware OK-Franklin AR-Haskell OK-Latimer OK-
Le Flore OK-Madison AR-Mayes OK-McIntosh OK-Muskogee OK-Nowata OK-
Okfuskee OK-Okmulgee OK-Osage OK-Ottawa OK-Pawnee OK-Pittsburg OK-
Pushmataha OK-Rogers OK-Sebastian AR-Sequoyah OK-Tulsa OK-Wagoner OK-
Washington OK-Washington AR-
453 AM CDT Thu May 27 2021

This Outlook is for Northwest and West Central Arkansas as well as
much of Eastern Oklahoma.

.DAY ONE...Today and Tonight.

TORNADO.
	RISK...Elevated.
	AREA...Mainly northeast Oklahoma.
	ONSET...After 3 pm.

SEVERE THUNDERSTORM.
	RISK...Significant.
	AREA...Eastern Oklahoma and northwest Arkansas.
	ONSET...Late morning to early afternoon.

	AREA AT GREATEST RISK...Northeast Oklahoma by late afternoon.

FLASH FLOOD.
	RISK...Limited.
	AREA...Eastern Oklahoma and northwest Arkansas.
	ONSET...This afternoon.

HEAVY RAIN.
	RISK...Elevated.
	AREA...Eastern Oklahoma and northwest Arkansas.
	ONSET...This afternoon.

DISCUSSION...
Thunderstorms may develop as early as late morning across parts
of northeast Oklahoma and northwest Arkansas. Given the increasing
instability, a few of these storms could be severe.

The more significant development is expected across southeast
Kansas into parts of northeast Oklahoma by mid to late afternoon.
These initial storms will pose a risk of tornadoes, damaging
winds and very large hail. Storms should eventually develop into
a complex and push southeast across the area Thursday evening
and overnight. Damaging winds will become the primary threat,
although there will be at least a low chance of tornadoes along
the leading edge of the line of storms. The severe weather threat
will end from north to south overnight.

SPOTTER AND EMERGENCY MANAGEMENT ACTION STATEMENT...
Activation of the Regional Spotter Network Expected.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.
FRIDAY...Thunderstorm Potential.
SATURDAY...No Hazards.
SUNDAY through WEDNESDAY...Thunderstorm Potential.

EXTENDED DISCUSSION...
Showers and thunderstorms may linger into early Friday across
portions of southeast Oklahoma. Severe weather is not expected.

After and dry and cool weekend, shower and thunderstorm chances
return by early next week.

weather.gov/tulsa contains additional information.

Special Weather Statement
National Weather Service Tulsa OK
1230 PM CDT Thu May 27 2021

OKZ054>056-271815-
Osage OK-Nowata OK-Washington OK-
1230 PM CDT Thu May 27 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN OSAGE...NORTHERN
WASHINGTON AND NORTHWESTERN NOWATA COUNTIES UNTIL 115 PM CDT...

At 1229 PM CDT, a strong thunderstorm was located 4 miles southeast
of Chautauqua, moving east at 40 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations in or near the path include...
Copan...                          Wann...
Hulah...                          Wah Sha She State Park...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

A Tornado Watch remains in effect until 700 PM CDT for northeastern
Oklahoma.

LAT...LON 3700 9564 3682 9566 3689 9622 3700 9621
TIME...MOT...LOC 1729Z 273DEG 34KT 3698 9611

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Special Weather Statement
National Weather Service Tulsa OK
1241 PM CDT Thu May 27 2021

OKZ057-058-063-271815-
Craig OK-Delaware OK-Ottawa OK-
1241 PM CDT Thu May 27 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN CRAIG...NORTHWESTERN
DELAWARE AND SOUTHWESTERN OTTAWA COUNTIES UNTIL 115 PM CDT...

At 1241 PM CDT, a strong thunderstorm was located over Vinita, moving
northeast at 30 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations in or near the path include...
Miami...                          Vinita...
Grove...                          Fairland...
Afton...                          Bernice...
Narcissa...                       Bernice State Park...
Ottawa...                         Twin Bridges State Park...

This includes Interstate 44 between mile markers 278 and 307.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

A Tornado Watch remains in effect until 700 PM CDT for northeastern
Oklahoma.

LAT...LON 3688 9479 3664 9466 3658 9500 3658 9501
      3657 9501 3654 9519 3667 9528
TIME...MOT...LOC 1741Z 247DEG 25KT 3662 9515

69