Severe Thunderstorm Warning 106, NWS Amarillo, TX

Area Forecast Discussion
National Weather Service Amarillo TX
704 PM CDT SAT MAY 21 2016

.Aviation... /For the 00z TAFs/
Thunderstorms are near Dalhart now and these will push east of the
terminal within the next couple of hours. Other storms located west-
southwest of Amarillo may approach the terminal closer to 01z but
instability will be decreasing so storms may diminish before
impacting the terminal. Another storm nearing Guymon has shown a
downward trend but may still result in irradic wind gusts as it
passes over/near the terminal between 00 and 01z.

Otherwise, warm/moist southerly flow may result in MVFR or IFR
stratus at all sites later tonight, with Amarillo having the greatest
likelihood. Stratus should clear by mid morning. Thunderstorms will
redevelop tomorrow afternoon and could impact either of the three
terminals. Prob30 will suffice for now until timing can be better
resolved.

BRB

&&

.Prev Discussion... /Issued 529 PM CDT SAT MAY 21 2016/

Mesoscale Update...
Convection has developed late this afternoon in a band from near
Stratford to Dalhart to far western Deaf Smith County. This is ahead
of a surface trough/sharpening dryline west of the New Mexico state
line, on the western edge of low-level theta-e axis. Movement of
individual cells is northeast at 25 to 30 mph. Latest RAP sounding
for KHDT needed little/no modification based on nearby surface obs.
Deep mixing has occurred with MLCAPE approaching 1,000 J/KG and
300-500 J/KG of CAPE in the hail growth zone. With the absence of
large CAPE in the hail growth zone, significant (2"+) hail sizes may
be difficult to achieve. Nevertheless, sufficient instability is
present for marginally severe hail in the strongest storms. Effective
Bulk Shear of around 35 knots is supportive of organized/persistent
updrafts and at least transient supercell characteristics. Radar has
shown the deepest cores indicitive of the strongest updrafts have not
sustained for long.

No significant trends upward are expected this evening. Eventually
isollobarically forced low level backing and decreased mixing will
lead to a surge of better moisture northwestward, but by then
diabatic cooling will be underway and the surface based instability
will lessen with a downward trend in convection expected. Until then
(probably around 9 or 10 PM) a severe hail/wind threat should
persist. We will evaluate new guidance and observational trends, the
potential for storms to sustain into the night and/or redevelop with
warm advection process. This seems unlikely at this time (see
previous discussion for reasoning).

BRB

Prev Discussion... /Issued 335 PM CDT SAT MAY 21 2016/

Discussion...
Thunderstorms that develop this afternoon across the western
Panhandles will move east this evening with at least a marginally
severe wind/hail threat persisting through late evening.
Deepening moisture and increasing precipitable water values per
short term guidance and trends in the upstream GPS PWAT sites,
combined with relatively slow storm motions are supportive of
locally heavy rainfall amounts and possibly flooding potential,
particularly later this evening in the southern Texas Panhandle. For
specifics on convective initiation and potential severe please see
the previously issued mesoscale discussion. Updates on mesoscale
evolution will be sent as needed through the afternoon and evening.

There is a decent signal in some of the models of warm/moist
advection process keeping convection going across the southern
portion of the Texas Panhandle through the night. Most of the
forecast soundings still show evidence of ridging/subsidence for
most of the night, but the eastward progression of the ridge may be
enough for some activity late especially in the southeast Texas
Panhandle where the WAA signal is maximized. Kept low probabilities
to account for this mainly focused on the southeastern Texas
Panhandle.

Modest ascent will overspread the area tomorrow in diffluent upper
flow regime. A sharpening dryline across the western Panhandles
should focus thunderstorm development during the afternoon in a
moderately unstable environment with MLCAPE of 2,000-2,500 J/KG. 0-6
km bulk shear of around 30 to 40 knots should be sufficient for
storm organization and supercells. Large hail and damaging winds
will be the primary threat although with relatively low LCL heights
generally less than 1,000m isolated tornadoes will be possible. The
best chance for a tornado would be during the evening as low level
jet strengthens causing low level shear to increase and before
significant boundary layer stabilization occurs.

Troughing to our west continues through mid-week before accelerating
eastward toward the Panhandles by the end of the week. Until then
mid-level momentum should allow the dryline to mix/sharpen across
the far eastern Panahandles and this convection should be limited to
this area. We will need to monitor trends in the short term guidance
as the time nears in case models are mixing the dryline too far east
as has been the case lately. This is a more synoptically active
scenario with fairly decent cross-boundary mean flow, thus the
reasoning for not adjusting westward at this time. If models trend
slower and more amplified with approaching truogh, we will likely
need to introduce at least low probabilities of convection in the
east portion of the Panhandles.

BRB

&&

.AMA Watches/Warnings/Advisories...
TX...NONE.
OK...NONE.

&&

3/14

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AMARILLO TX
310 PM CDT SAT MAY 21 2016

OKZ001>003-TXZ001>020-220815-
CIMARRON-TEXAS-BEAVER-DALLAM-SHERMAN-HANSFORD-OCHILTREE-LIPSCOMB-
HARTLEY-MOORE-HUTCHINSON-ROBERTS-HEMPHILL-OLDHAM-POTTER-CARSON-
GRAY-WHEELER-DEAF SMITH-RANDALL-ARMSTRONG-DONLEY-COLLINGSWORTH-
310 PM CDT SAT MAY 21 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE TEXAS AND OKLAHOMA
PANHANDLES.

.DAY ONE...THIS EVENING AND TONIGHT.

ISOLATED TO SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS THE TEXAS AND
OKLAHOMA PANHANDLES THIS EVENING THROUGH AT LEAST EARLY TONIGHT.
SOME STORMS THAT DEVELOP WILL HAVE THE POTENTIAL TO BECOME STRONG TO
SEVERE WITH LARGE HAIL AND DAMAGING WINDS BEING THE PRIMARY HAZARDS.
HEAVY RAINS WILL LIKELY OCCUR...POSSIBLY LEADING TO FLOODING OR FLASH
FLOODING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS THE OKLAHOMA AND TEXAS
PANHANDLES SUNDAY. SEVERE THUNDERSTORMS ARE POSSIBLE WITH LARGE HAIL
AND DAMAGING WINDS BEING THE PRIMARY HAZARDS. ISOLATED TORNADOES
ARE ALSO A POSSIBILITY.

ISOLATED THUNDERSTORMS MAY FORM ACROSS THE FAR EASTERN TEXAS AND
OKLAHOMA PANHANDLES MONDAY AFTERNOON AND AGAIN TUESDAY AFTERNOON.
SOME OF THESE STORMS COULD BECOME SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THROUGH EARLY TONIGHT. SPOTTER
GROUPS AND EMERGENCY MANAGEMENT OFFICIALS ACROSS THE OKLAHOMA AND
TEXAS PANHANDLES SHOULD CONTINUE TO MONITOR THE LATEST FORECASTS AND
BE PREPARED FOR POSSIBLE ACTIVATION SUNDAY AFTERNOON AND EVENING.

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AMARILLO TX
747 PM CDT SAT MAY 21 2016

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

0744 PM     HAIL             3 S HARTLEY             35.84N 102.40W
05/21/2016  E2.00 INCH       HARTLEY            TX   TRAINED SPOTTER

&&

EVENT NUMBER AMA1600385

BRB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AMARILLO TX
748 PM CDT SAT MAY 21 2016

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

0710 PM     HAIL             2 E SIMMS               35.03N 102.62W
05/21/2016  E2.00 INCH       DEAF SMITH         TX   TRAINED SPOTTER

            HALF DOLLAR TO HEN EGG HAIL.

&&

EVENT NUMBER AMA1600386

COCKRELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AMARILLO TX
750 PM CDT SAT MAY 21 2016

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

0747 PM     HAIL             1 SE HARTLEY            35.88N 102.38W
05/21/2016  E1.75 INCH       HARTLEY            TX   BROADCAST MEDIA

            PING PONG BALL TO GOLF BALL SIZE HAIL.

&&

EVENT NUMBER AMA1600388

BRB

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AMARILLO TX
756 PM CDT SAT MAY 21 2016

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

0749 PM     HAIL             10 SE SIMMS             34.95N 102.51W
05/21/2016  M1.00 INCH       DEAF SMITH         TX   STORM CHASER

            0.95 INCH DIAMETER HAIL MEASURED WITH CALIPERS.

&&

EVENT NUMBER AMA1600389

BRB