EF0 tornado, South Bend to Graham Muni Arpt, Texas, March 18, 2020

Area Forecast Discussion
National Weather Service Fort Worth TX
742 PM CDT Wed Mar 18 2020

.SHORT TERM... /NEW/
/Tonight through Thursday Night/

The main concern in the short term will be the threat for severe
storms and heavy rain/flash flooding.

A non-trivial short term forecast is shaping up across the area.
Our 2100 UTC FWD RAOB indicate a pretty stout cap near 15 C just
above 850mb. Large scale ascent certainly acted upon this cap and
most if not all inhibition was gone along the I-35 corridor per
our 0000 UTC RAOB. In house convective parameters indicated,
however, that a wedge of slightly more stable air did exist
between the Metroplex and the Big Country and this may explain
recent trends in the Eastland/Stephens County storm as they
appear to have become a bit less surface based. In the near term,
it's probable that the threat will transition more to large hail.
If storms are able to become more surface based, the damaging
wind and tornado risk will increase. The damaging wind threat may
materialize with activity moving out of the Concho Valley, but
we'll need to monitor trends.

The evolution of convection through the evening hours
unfortunately remains somewhat nebulous. Short term CAMs have
struggled, but overall think that the coverage of activity will be
limited (at least across our North Texas counties) as we await
stronger forcing for ascent from Mexico. I've confined the
greatest PoPs to areas near and west of a Goldthwaite to Fort
Worth to Gainesville line through at at least 0300 UTC or 2200
CDT. During this time, the 925-850mb LLJ will increase upwards of
35-45 knots. This will result in a sizable increase in the
hodograph with 0-1 km shear near 30 knots per some forecast
soundings. MLCAPE values remain near 1500 J/kg. 0-3km CAPE values
are generally less than 100 J/kg and some forecast soundings do
indicate some slight inhibition just above the surface (which
could keep activity slightly more elevate). The lack of higher
0-3km CAPE and slight warming aloft coupled with the lack of
strong/focused ascent makes me believe that perhaps the window for
a high impact severe weather event may be closing (though not
completely shut). *IF* storms can overcoming the warming aloft,
realize the instability and increasing low level shear, there will
be the potential for damaging straight line winds (possibly close
to 70mph), large hail and potentially a tornado or two. As such,
we'll let Tornado Watch #54 continue before making any changes.

Later tonight, a conveyor of 55-65 knot mid-level flow will nose
in from the southwest. Strengthening low level WAA will help
result in the proliferation of additional showers and storms (and
we may be seeing the start of that across the Big Country/Concho
Valley). Given the deep layer shear and instability, there will be
an attendant severe weather risk with this activity, but it'll
largely be confined to that of damaging winds and large hail. The
tornado risk will remain non-zero, however.

In addition to severe weather, there will be a heightened risk
for heavy rain and flash flooding. The 0000 UTC FWD RAOB noted a
PWAT of around 1.63 in and given that MRMS indicates 4-5" of rain
has fallen in the last 24 hours across parts of the area
(Stephens/Palo Pinto County). Given the antecedent conditions,
runoff efficiency will likely be near 100% and I anticipate that
any additional rain will prompt some short fused flood warning
products.

Bain

&&

.LONG TERM... /Issued 321 PM CDT Wed Mar 18 2020/
/Thursday Through Next Tuesday/

Well, after our first round of active weather the past 24 hours,
the second round coming in tonight will extend through the
morning hours Thursday area-wide, with lingering lower rain/storm
chances in the East on Thursday afternoon. Thursday morning will
see a similar set up to the previous morning, with a weakening
storm cluster moving east across predominantly areas north of
I-20. Some low coverage of morning showers and isolated storms may
also be ongoing across parts of Central Texas in the warm sector.
There will still be a low risk of severe weather -- that being
primarily damaging winds, along with small hail and frequent
lightning. The higher end concern, however will be the pockets of
heavier rainfall and yes, more flooding, including instances of
flash flooding within the current Flash Flood Watch area that
continues through 7 PM from the DFW Metroplex to the Red River
Valley. These areas continue to remain supersaturated after
several rounds of heavier rainfall the past 1-2 weeks, including
the primer we experienced early today.

By afternoon, a pre-frontal surface trough will surge in from the
west and just in advance of a cold front surging southward down
the Central High Plains of Eastern CO/Western KS. Though a
reprieve in the heavier early morning rainfall likely comes to end
with a brief lull during the late morning/midday hours, it
appears renewed, mostly scattered convective development will be
possible along and ahead of the surface trough and with the
ejection of the main mid level shortwave exiting out of the
Central Rockies. If the convective mid-upper level anvil debris
from the morning system can warm and disperse and allow for ample
daytime heating by afternoon, a strong to severe storm cannot be
ruled out in advance of the surface trough. Of course this will be
conditional on our environment recharging with any afternoon
insolation and weakening large-scale subsidence from the morning
complex and heavy rainfall. That said, may areas should warm well
into the 70s to even lower 80s.

The cold front will arrive during the overnight hours Friday
morning with lingering convective chances briefly across our East
Texas counties on Thursday evening. However, just as our northern
stream begins to dampen and quiet down, the subtropical jet
stream then becomes active and draw mid-upper level tropical
moisture from the equatorial Pacific. Periodic, though subtle,
mid level impulses will ripple across Central and South Texas
Friday through much of the weekend. Though temperatures will
certainly cool down at the surface, the frontal inversion will be
relatively shallow with lift and moisture from the Gulf of Mexico
overriding this boundary and up across much of Central Texas.
We'll see the left-exit region of a subtropical jet maximum result
in scattered to widespread showers with a chance of
embedded/elevated thunderstorms south of the I-20/30 corridors
both days. Though any threat for severe weather is low, we may
need to begin monitoring Central Texas's rainfall closely as
they'll see a few rounds of more substantial rainfall on Friday,
then again Saturday night. Things begin to quiet down for at least
a better and warmer Sunday, as the mid level flow dampens and
with subsidence and partial clearing allowing for afternoon
temperatures to warm into the 60s for all but the far northeast
counties.

The early half of next week looks flat out Springlike as our flow
becomes near zonal on Monday, before amplifying into a shortwave
ridge set up in advance of a system organizing in the East Pacific
Ocean and dropping south off the CA coastline. Though a mostly
diurnal, general thunderstorm or shower is possible in the richer
moisture in East Texas each day, this activity will be the
exception to the rule. Look for highs to warm into the 70s Monday,
before warming into the mid 70s Northeast to the lower 80s
Southwest on Tuesday.

05/

&&

.AVIATION... /NEW/
/00 UTC TAF Cycle/

Concerns---TSRA potential and ceiling trends.

Confidence---Medium.

VFR continues at all TAFs and is expected through at least 0600
UTC. VCTS prior to 0600 UTC appears unlikely at TAF sites as the
best/most focused ascent remains west of the area. We'll keep an
eye on convective trends, however.

As the main trough approaches from the southwest, I expect a
proliferation of SHRA/TSRA. This activity will advance from the
west and southwest during the predawn hours. Fortunately, it
appears that SHRA/TSRA will occur during a time in which air
traffic is at a minimum. Accompanying SHRA/TSRA will be the
potential for gusty west winds and MVFR cigs, especially at the
Metroplex TAFs. Confidence in TSRA at Waco is low, so for now,
I'll only advertise VCTS.

VCTS will linger into the mid-morning hours on Thursday and could
result in some impacts to inbound traffic along the Bonham/Cedar
Creek cornerposts as well as eastbound departures. VFR will return
by midday with south winds near 18 knots. Some winds may gust as
high as 30 knots.

Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    66  80  51  55  41 /  80  70  20  40   5
Waco                67  81  54  56  44 /  60  60  50  80  10
Paris               66  76  52  55  40 /  50  90  20  40   5
Denton              67  78  48  55  39 /  90  70   5  30   5
McKinney            67  78  50  55  39 /  70  80  10  40   5
Dallas              67  80  53  57  42 /  70  80  20  40   5
Terrell             68  78  52  56  42 /  50  80  30  60  10
Corsicana           67  78  55  59  44 /  50  80  40  80  20
Temple              67  80  54  59  44 /  50  50  70  80  10
Mineral Wells       65  78  47  55  37 / 100  50  10  20   5

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday evening for TXZ091>095-
100>107-115>123-129>134-141.

&&

24/79

Hazardous Weather Outlook
National Weather Service Fort Worth TX
118 PM CDT Wed Mar 18 2020

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-191200-
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-
118 PM CDT Wed Mar 18 2020

This Hazardous Weather Outlook is for North and Central Texas.

.DAY ONE...This Afternoon and Tonight.
Isolated to scattered thunderstorms are possible late this afternoon
and early evening mainly north of I-20 and west of I-35 and 35 West.
Damaging winds, large hail, and isolated tornadoes are possible with
these storms, especially with discrete storms that develop very late
this afternoon through the evening hours.

Another round of thunderstorms, more in the form of a line or
complex, will move into North Texas around or just after midnight,
then move from west to east across especially those areas along and
north of I-20. Some storms may be severe with damaging winds being
the main hazard. Heavy rainfall over already saturated soils will
likely lead to an increasing flash flood threat through daybreak
Thursday and primarily north of I-20.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.
Rain and thunderstorms will linger across parts of East Texas on
Thursday, especially during the morning. A few thunderstorms could
be strong to severe and contain heavy rainfall that may lead to
additional flooding or flash flooding.

.SPOTTER INFORMATION STATEMENT...
Spotter activation may be requested across parts of North Texas
beginning late this afternoon and continuing into tonight. More
limited activation can't be ruled out further south across Central
Texas.

Special Weather Statement
National Weather Service Fort Worth TX
803 PM CDT Wed Mar 18 2020

TXZ100-101-116-190200-
Palo Pinto TX-Young TX-Jack TX-
803 PM CDT Wed Mar 18 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN YOUNG...SOUTHERN
JACK AND NORTHEASTERN PALO PINTO COUNTIES UNTIL 900 PM CDT...

At 802 PM CDT, Doppler radar was tracking a strong thunderstorm near
Graford, or 15 miles southeast of Graham, moving northeast at 30 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

 Locations impacted include...
Jacksboro and Graford.

A Tornado Watch remains in effect until midnight CDT for north
central Texas.

LAT...LON 3343 9792 3303 9793 3300 9800 3300 9805
      3298 9806 3285 9840 3300 9857
TIME...MOT...LOC 0102Z 234DEG 24KT 3298 9835

Hernandez

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE FORT WORTH TX
919 PM CDT WED MAR 18 2020

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

0909 PM     TORNADO          6 SE JACKSBORO          33.16N  98.10W
03/18/2020                   JACK               TX   TRAINED SPOTTER

            TORNADO REPORTED NORTH OF HIGHWAY 199 6 MILES SOUTHEAST
            OF JACKSBORO