Special Weather Statement, NWS Fort Worth, TX

Area Forecast Discussion
National Weather Service Fort Worth TX
323 PM CST Sun Feb 19 2017

.DISCUSSION...

Water vapor imagery shows the strong upper low spreading across
northwest Mexico and into far West Texas this afternoon. Height
falls ahead of the system spreading across much of Texas are
indicative of increasing forcing for ascent. At the surface...a
rather expansive warm sector has developed this afternoon as cloud
cover has thinned and temperatures have warmed into the 70s and
lower 80s. An effective warm front appears to be positioned from
near Graham to Denton and tailing off to the southeast from there.
South of the boundary...surface based instability has increased
to between 1000-1500 J/kg over the last couple of hours. There is
still a rather strong capping inversion in place although 20Z
analysis across North Texas suggests that it is weakening. As
stronger forcing for ascent spreads a little farther east into the
early evening hours...would expect the cap to be completely
lifted allowing for surface based convection to develop. All of
the high resolution guidance suggests that this will happen in the
next 2-3 hours (5-6 pm).

Convective initiation will most likely occur to the northwest of
the Metroplex in an area of strong low level warm advection by 22Z.
At the surface...weak troughing is noted from near Lubbock
eastward to just north of Graham. This is where low level
convergence appears to be maximized. This initial activity should
develop in an area of moderate instability beneath steep mid level
lapse rates and strong deep layer shear and will pose the greatest
potential to become severe. Initial thunderstorms are likely to be
supercellular in nature with a large hail and perhaps a tornado
threat. Low level flow isn't optimal for a more significant
tornado threat and the unidirectional wind profile suggests that
storms would tend to try to organize into line segments rather
quickly. However...low level flow may be backed near the warm
front resulting in a localized favorable shear profile for
tornadoes through this evening. This threat continues to be
highest from near Fort Worth and areas west of there across our
CWA (roughly an area from Eastland to Stephenville to Fort Worth
to Gainesville and northwest of there).

Later tonight in the 7-10pm timeframe...a more expansive area of
showers and thunderstorms is likely to develop across Southwest
Texas into Central Texas and will spread north into a linear MCS
around midnight. This should be the main area of precipitation
which will march east during the overnight hours. The severe
weather threat should diminish during this time with the loss of
heating and waning surface based instability...however...wind
fields will remain sufficiently strong for some isolated damaging
wind gusts with the strongest cells or bowing line segments. The
main threat during the overnight hours will be heavy rainfall.
Storms should be fairly efficient rainfall producers and will move
in a south to north motion...allowing for some localized training
of convection. It's in these areas that some isolated rainfall
amounts could exceed 3 inches. Minor flooding issues would likely
result especially in low lying or urban areas. The heaviest
rainfall will likely occur across areas east of I-35 late tonight
into early Monday morning. At this time...given the progressive
nature of the upper low...we'll hold off on a flash flood watch
across our area.

Precipitation is likely to continue across the eastern half of
the CWA during the morning hours on Monday before ending from west
to east around midday. There is not a substantial push of dry air
into the region behind this system...so low clouds may linger for
much of the day especially across the eastern half of the CWA.
Clouds should finally clear the region on Tuesday with
temperatures warming back up into the upper 70s and lower 80s
through mid week. A weak front will move through on Friday and
bring temps back down closer to normal but no additional
precipitation is expected.

Dunn

&&

.AVIATION...
/ISSUED 1244 PM CST Sun Feb 19 2017/
/18Z TAFs/

The surface layer was unable to cope with the sudden surge of
Gulf moisture at the coolest time of the day, and widespread LIFR
ceilings and IFR/LIFR dominated the daylight hours of the morning.
Although such conditions rarely improve so quickly this time of
year, this air mass is better suited to April than February. That
said, there remains the potential for strong/severe thunderstorms
tonight. The remainder of the afternoon will be dominated by MVFR
ceilings, and showers will develop as rich moisture arrives at
850mb. However, the deep convection will initiate across western
portions of North Texas, particularly if the low cloud deck is
able to allow some sunshine through. It still appears that these
scattered thunderstorms will have a tendency to congeal into a
line and approach the I-35 corridor around midnight. This may be
during the complex's transition from a severe threat to a heavy
rain threat, but this will not preclude thunder at the I-35
corridor TAF sites during the early morning hours Monday. Showery
rain will continue during the morning push, which should have
minimal adverse impacts.

25

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    64  71  52  77  50 / 100  50   5   0   0
Waco                62  70  51  76  48 / 100  50   5   0   0
Paris               63  68  53  73  50 /  80 100  10   5   0
Denton              62  71  48  76  47 / 100  40   5   0   0
McKinney            63  70  50  75  48 / 100  60  10   0   0
Dallas              63  71  53  77  51 / 100  50   5   0   0
Terrell             63  71  52  76  50 / 100  70  10   0   0
Corsicana           63  70  54  75  52 / 100  70  10   5   0
Temple              61  72  51  77  48 / 100  40   5   0   0
Mineral Wells       57  74  47  77  46 / 100  10   5   0   0

&&

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

Hazardous Weather Outlook
National Weather Service Fort Worth TX
348 PM CST Sun Feb 19 2017

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-201200-
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-
348 PM CST Sun Feb 19 2017

This Hazardous Weather Outlook is for North and Central Texas.

.DAY ONE...Tonight.
Thunderstorms will develop across western portions of North Texas
into the evening hours, spreading east across the region overnight.
Through this evening, some of the storms could become strong or
severe, primarily along and west of the I-35 corridor. Damaging wind
and hail will be the main hazards, but there will also be a tornado
threat.

A larger area of rain is expected to develop across the region
tonight. Minor flooding will be the primary concern overnight.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.
A large area of rain with embedded thunderstorms will be ongoing
Monday morning east of the I-35 corridor, posing some flooding
concerns. The thunderstorms and associated heavy rain will exit the
region Monday afternoon.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is likely through the evening hours, primarily
along and west of the I-35 corridor.

25

Special Weather Statement
National Weather Service Fort Worth TX
529 PM CST SUN FEB 19 2017

TXZ115-116-200030-
Palo Pinto TX-Stephens TX-
529 PM CST SUN FEB 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN STEPHENS AND NORTHWESTERN
PALO PINTO COUNTIES UNTIL 630 PM CST...

At 528 PM CST, Doppler radar was tracking a strong thunderstorm near
Necessity, or 8 miles northwest of Ranger, moving north at 30 mph.

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

Locations impacted include...
Eastern sides of Breckenridge, Necessity, Gunsight, Crystal Falls
and Possum Kingdom State Park.

LAT...LON 3295 9846 3251 9860 3251 9888 3296 9890
TIME...MOT...LOC 2328Z 195DEG 26KT 3257 9876

24-Bain

Special Weather Statement
National Weather Service Fort Worth TX
621 PM CST SUN FEB 19 2017

TXZ100-200045-
Young TX-
621 PM CST SUN FEB 19 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN YOUNG COUNTY UNTIL
645 PM CST...

At 620 PM CST, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Woodson, or 11 miles east of Throckmorton, moving
northeast at 55 mph.

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

Locations impacted include...
Olney...Murray and Newcastle.

LAT...LON 3340 9895 3339 9857 3300 9894 3301 9895
TIME...MOT...LOC 0020Z 205DEG 48KT 3313 9899

24-Bain