Severe Thunderstorm Warning 233, NWS Fort Worth, TX

Area Forecast Discussion
National Weather Service Fort Worth TX
705 PM CDT Fri May 19 2017

.AVIATION...
Thunderstorms continue to erupt in two general areas both
southwest and northwest of North Texas TAF sites. The active
weather is associated with an upper low over Colorado, a shortwave
rotating around the southeast flank of the low and an approaching
cold front.

The northeasterly storm motion in the ongoing activity means that
the scattered strong to severe convection approaching Glen Rose
will begin to affect the Ft Worth area airports around 01Z or so,
then DFW and DAL shortly thereafter. For the 01Z to 03Z
timeframe, thunderstorm coverage in the Metroplex may remain low
enough to preclude a tempo or prevailing group, so will keep VCTS
going to account for the scattered activity. Forcing from the
advancing shortwave will increase as we proceed later into the
evening and prevailing TS beginning 03Z seems warranted. Storm
coverage will likely increase as the cold front moves in from the
northwest, and a tempo group from 06-09Z will be for the latest
thinking of when the front and associated line of storms move
through the DFW area.

For KACT, it appears that storms should remain west and northwest
for the time being, but should increase in the area around 06Z as
lift increases. A tempo group has been added from 09-12Z when the
front moves into the area.

30

&&

.UPDATE...
Did a quick update to account for backed flow and stronger
surface winds than previously forecast. Many locations are
gusting over 30 MPH out of the southeast, which if nothing else
will at least keep the severe thunderstorm and tornado threat
going within tornado watch 249 (which remains in effect until 11
PM). The latest indications are that the scattered convection just
west of the region will eventually approach the I-35 corridor 8
to 10 PM. Another round of storms will be possible after midnight
as the strongest forcing associated with a shortwave disturbance
arrives and a slow moving cold front moves in from the northwest.
The severe threat should continue overnight as the low level jet
develops, but the threat will likely be lower due to the loss of
diurnal instability. A locally heavy rain threat can also be
expected overnight.

30

&&

.PREV DISCUSSION... /ISSUED 225 PM CDT Fri May 19 2017/
Our slow-moving upper low continues to shift east across CO this
afternoon, with disturbances active within strong southwest flow
aloft over the western half of the state of TX. Shortwave energy
will continue to round the base of the upper low across the state
and northeast across OK through the weekend. At the surface, a
surface low was located between Midland and Lubbock, with a surface
cold front progressing southward across the OK/TX Panhandles. This
feature will be an additional player in convective developing late
tonight and lingering across Central TX later on Saturday and
possibly into Saturday night.

A corridor of enhanced isentropic lift and jet forcing aloft
remains centered from West-Central TX, northeast across the South
Plains and into southern and eastern OK this afternoon. Per latest
high res model guidance (3km NAMNEST the best on initialization
w/the HRRRx a close second), we expect our main threat through
early evening to remain west of I-35 and particularly north of
I-20. Model sounding forecasts across this area indicate plenty of
available instability(including mid level lapse rates 7-8 deg
C/km) and wind shear for severe storms containing very large hail
at times, along with damaging winds. Initial curved hodographs in
the lowest 5-10 kft do indicate a window of tornadic potential
through at least mid evening, especially with any discrete
activity, along with ample, sub-cloud instability to draw
horizontal vorticity surface upward into any rotating updrafts.

As the cold front enters our northwest CWA mid-late evening,
early indications are that discrete severe storms could congeal
into a slow, east-southeast moving QLCS or broken squall line
through the overnight hours, before weakening around daybreak
Saturday morning. The slow-movement of the cold front, along with
potential training of convection, heavier rain rates within an
area of 1.5 or greater PWATs will likely result in between 1-3
inches of rainfall along and north of I-20. We can't rule out
isolated higher amounts. Since we're so close to the event and
with some uncertainty on rainfall amounts, a Flash Flood Watch
will not be hoisted. That said, localized flash flooding is
certainly possible tonight and early Saturday, especially urban
areas around the DFW Metroplex, northeast through Sherman/Denison.

The surface cold front, assisted by storm outflow and the gradual
eastward progression of the upper low across the Central Plains
will continue to progress the front through Central TX during the
day Saturday into Saturday night. Better rain and convective
chances will accompany the cold front southward into East and
Central TX during this time. A few strong to severe storms are
possible where any instability can establish itself, though
coverage of severe weather should be much less than recent days.
In addition, better ascent and wind shear will be north of the
region, lessening the large-scale ascent across the area.
Depending on how fast the cold front moves southeast, areas of
heavy rain and flooding potential are uncertain. If the front is
slower, then more potential for heavier rains will exist. If the
front is more progressive, then flooding will be less likely
across Central Texas Saturday and Saturday night.

Drier low level air should continue to filter into the region
from the north the latter half of the weekend, as flow aloft
dampens into a westerly regime in behind the departing upper level
trough. Periodic energy moving east across Central TX may continue
some off and on showers and a few thunderstorms, but any flash
flood and severe weather threat will have ended. Weak upper
troughing and surface high pressure across the area will keep
sensible weather relatively quiet and cooler Sunday into Monday,
before the surface high shifts east.

Gradual low level moisture return will occur Monday night, ahead
of another shortwave trough aloft and associated cold front
arriving on Tuesday. Tuesday should be our next good, but brief
shot for showers and storms, though right now the thermodynamic
environment is too unknown and currently not looking overly
unstable for any severe weather. A cooler and brisk day Wednesday.
Shortwave ridging aloft and returning southerly surface winds the
end of the week will bring more seasonal late May warmth back to
the area. Rain chances look close to nil as well.

05/

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    68  81  59  82  62 /  80  50  30  10   5
Waco                70  83  61  82  63 /  60  70  60  20  20
Paris               68  79  56  80  58 /  70  60  30   5   0
Denton              65  78  55  82  58 /  80  40  20   5   5
McKinney            68  80  57  82  59 /  80  50  30   5   5
Dallas              70  82  61  83  63 /  80  50  40  10  10
Terrell             70  82  60  82  61 /  70  60  50  10  10
Corsicana           70  83  61  81  63 /  60  70  60  20  10
Temple              70  84  61  81  63 /  50  60  60  30  20
Mineral Wells       64  77  55  82  58 /  80  30  20   5  10

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

Hazardous Weather Outlook
National Weather Service Fort Worth TX
301 PM CDT Fri May 19 2017

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-201230-
Montague-Cooke-Grayson-Fannin-Lamar-Young-Jack-Wise-Denton-Collin-
Hunt-Delta-Hopkins-Stephens-Palo Pinto-Parker-Tarrant-Dallas-
Rockwall-Kaufman-Van Zandt-Rains-Eastland-Erath-Hood-Somervell-
Johnson-Ellis-Henderson-Comanche-Mills-Hamilton-Bosque-Hill-Navarro-
Freestone-Anderson-Lampasas-Coryell-Bell-McLennan-Falls-Limestone-
Leon-Milam-Robertson-
301 PM CDT Fri May 19 2017

This Hazardous Weather Outlook is for North and Central Texas.

.DAY ONE...This Afternoon and Tonight.
A few thunderstorms are expected to develop (and continue) across
western North Texas and the counties near the Red River through the
rest of the afternoon. Large hail would be a key threat with the
strongest of these cells, with tornadoes also a possibility.

This evening, thunderstorms northwest of a Paris to Dallas to
Goldthwaite line should expand significantly in areal coverage and
intensity. This activity will be forming along and ahead of a cold
front approaching from the northwest. Multiple forms of convective
mode are possible through at least midnight, producing large hail and
damaging straight line winds. The environment will also be conducive
for one or more tornadoes, particularly in areas northwest through
northeast of the Metroplex.

Thunderstorms will continue intermittently through daybreak Saturday,
resulting in the possibility of multiple rounds of heavy rain. A few
spots may receive anywhere from 2-3 inches of rainfall, which could
result in some isolated flash flooding late tonight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.
Thunderstorm chances will continue through Saturday evening,
especially south and east of the Metroplex. Some thunderstorms may be
strong or briefly severe south of a Temple to Athens line, but
widespread impacts are not expected. The unsettled weather pattern
will continue Monday and Tuesday with additional thunderstorm chances
both days.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is likely by late this afternoon and
evening...particularly along and west of I-35. Additional activations
may be required farther east late tonight as thunderstorms spread
east of I-35.

Bradshaw

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FORT WORTH TX
719 PM CDT FRI MAY 19 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0719 PM     HAIL             2 S HICO                31.95N  98.03W
05/19/2017  E0.88 INCH       HAMILTON           TX   TRAINED SPOTTER

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FORT WORTH TX
725 PM CDT FRI MAY 19 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0724 PM     HAIL             4 S HICO                31.92N  98.03W
05/19/2017  E1.00 INCH       HAMILTON           TX   LAW ENFORCEMENT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FORT WORTH TX
730 PM CDT FRI MAY 19 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0728 PM     HAIL             HICO                    31.98N  98.03W
05/19/2017  E1.75 INCH       HAMILTON           TX   BROADCAST MEDIA

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FORT WORTH TX
820 PM CDT FRI MAY 19 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0817 PM     HAIL             18.03 ENE HAMILTON      31.80N  97.93W
05/19/2017  E1.00 INCH       HAMILTON           TX   FIRE DEPT/RESCUE

            VOLUNTEER FIRE DEPARTMENT REPORT QUARTER SIZE HAIL NEAR
            CRANFILLS GAP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FORT WORTH TX
901 PM CDT FRI MAY 19 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 PM     HAIL             PURMELA                 31.48N  97.97W
05/19/2017  E1.75 INCH       CORYELL            TX   BROADCAST MEDIA

Special Weather Statement
National Weather Service Fort Worth TX
928 PM CDT FRI MAY 19 2017

TXZ100-200300-
Young TX-
928 PM CDT FRI MAY 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN YOUNG COUNTY UNTIL
1000 PM CDT...

At 928 PM CDT, Doppler radar was tracking a strong thunderstorm near
Megargel, or 9 miles west of Olney, moving northeast at 40 mph.

Nickel size hail will be possible with this storm.

Locations impacted include...
Olney.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so closely monitor for additional
information or possible warnings from the National Weather Service.

&&

A tornado watch remains in effect until 1100 PM CDT for north central
Texas.

LAT...LON 3340 9895 3340 9861 3326 9861 3317 9895
TIME...MOT...LOC 0228Z 243DEG 34KT 3338 9892

JLDunn