Severe Thunderstorm Warning 20, NWS Amarillo, TX

Area Forecast Discussion
National Weather Service Amarillo TX
117 PM CDT Wed Apr 17 2019

.MESOSCALE UPDATE...
...Severe weather and localized flooding expected today...

* Synoptic Overview: An upper low located over the White Sands, NM
  area is progressing eastward this afternoon, with reflection of
  a surface low starting to develop southwest of Hereford, TX.
  Water vapor is showing multiple shortwave trofs rotating around
  the parent upper low, with one such feature extending from
  northeastern New Mexico southeast to Happy, TX. Subsidence
  behind this shortwave is expected to get pinched off as another
  shortwave following from Plainview, TX towards Santa Rosa, NM
  moves towards the northeast.

* Mesoscale: Surface cold front has progressed through most of the Texas
  Panhandle and has since stalled just south of Hereford, TX
  northeast to Lefors, TX and points northeast of there. It is not
  expected that this front will make any further forward
  progression this afternoon. A surface dryline is making eastward
  progression into the southern Texas Panhandle, and is currently
  draped along the Interstate 27 corridor. Latest available data
  from the special sounding launch at 17/18Z shows a significant
  dry layer below H6 and a capping inversion around H8. In
  addition, very steep adiabatic lapse of 8 to 9 degrees C/km will
  be supportive of rapid growth on any storms that can form along
  the frontal boundary or in the warm, moist sector. As insolation
  from sunlight at KAMA has not occurred, forcing along the quasi-
  stationary boundary will be dependent upon dynamical and
  mechanical lift provided by passing short wave features.
  Meanwhile, ahead of the front and dryline in the southeast Texas
  Panhandle, convective activity will be supported by MLCAPE
  presently in the 1000-2000 J/kg range with dew point
  temperatures in the upper 50s to low 60s. Wind shear values are
  expected to increase through the afternoon and evening hours as
  the left jet exit region begins to overspread the southeastern
  Panhandles. Latest hi-res CAMs analysis suggests that 0-6km bulk
  shear values of 45 to 50 kts will increase to around 50 to 60
  kts late this afternoon and evening.

* Threats: Hail size up to the size of 2 inches may be realized in
  the far eastern Texas Panhandle in the warm, moist airmass ahead
  of both the frontal boundary and dryline. Further west, hail
  sizes may approach the size of golf balls. The hail threat will
  largely exist in these regions through about 7 to 9 PM this
  evening. Wind threats, though, will be conditional on
  proximity to the frontal boundary and the presence of lower
  level inversion layers. Much like the hail threat, expect that
  the greatest threat will be in the far eastern Texas Panhandle
  with speeds up to 70 MPH being possible. Finally, the tornado
  threat will be conditional on storms becoming surface based for
  any period of time, with this threat being most likely in the
  warm, moist sector across the east and southeastern sections of
  the Texas Panhandle. Once the low level jet kicks in closer to
  sunset, any existing storms could potentially have increased
  lower level spin to work off of in the 6 to 9 PM CDT window.
  Meanwhile, along the cold front and near the dryline in the
  central and southwestern Texas Panhandle, brief spin up
  tornadoes cannot be ruled out as localized boundary interactions
  from storms could occur. By late this evening, the severe
  weather potential will be out of the area.

* Hydrology: The presence of a quasi-stationary frontal boundary
  draped southwest to northeast across the Texas Panhandle, along
  with overrunning forcing with passing shortwaves, will support
  the potential for storms training over the same areas. PW values
  are not the best, with anywhere from 0.50" in the southwest to
  central Panhandles and 1.00" in the far southeast. With that
  said, any storms that develop along the boundary will have storm
  motion favoring the northeast with more storms developing
  behind it. Given the drier airmass that these storms have to
  overcome at first, precipitation amounts will be light at best.
  As storms precipitate and moisten the dry environments in the
  southwestern and central Texas Panhandle, precipitation amounts
  should increase and be supportive for spots of localized
  flooding.

* Timing & Location: Present thunderstorm activity is moving into
  southern Texas Panhandle this afternoon. This activity should
  remain isolated in nature for the next couple of hours. However,
  the next shortwave trough that moves in will be the one to kick
  off activity across the south and central Texas Panhandle
  around 3 PM CDT. This same shortwave trough feature will make it
  to the northeastern Panhandles around 4 to 6 PM CDT, starting
  storms in that area. The frontal boundary and dryline will start
  to make eastward and southeastward progress around sunset,
  quickly making it into the main part of Oklahoma by 8 to 10 PM CDT
  tonight. Lingering thunderstorm activity will persist through
  about 1 to 3 AM CDT tomorrow morning.

* Summary: A complicated forecast scenario is developing this
  afternoon, with strong to severe thunderstorms possible across
  most of the region. Storms have formed and more will form around
  3 PM CDT along and north of the Interstate 40 corridor. As the
  low level jet kicks in around 5 to 9 PM CDT, storms will develop
  in the southeastern Texas Panhandle, quickly congealing into a
  line as it moves east through about 9 PM CDT. Severe weather and
  localized flooding potential should diminish rapidly thereafter,
  with lingering shower and thunderstorm activity continuing
  through about 1 to 3 AM Thursday morning.

Bieda

&&

.PREV DISCUSSION... /Issued 1239 PM CDT Wed Apr 17 2019/

AVIATION...
18Z Issuance...VFR conditions will likely degrade to MVFR for the
southeastern 2/3 of the area with thunderstorms for the afternoon
after 21Z through 06Z. DHT and GUY may see some VCTS but
confidence is low for timing a thunderstorm to hit as they will be
behind the front in drier air. Northerly winds will persist
through period with gusts of 25-35kts likely and stronger gusts
within thunderstorms possible. Low clouds should start to move out
towards mid-morning.

Beat

PREV DISCUSSION... /Issued 316 AM CDT Wed Apr 17 2019/

SHORT TERM...Today and Tonight...
An upper level low over the desert southwest will continue to move
east northeast through today and tonight.  As this upper low moves
into eastern New Mexico by mid afternoon a jet streak is expected to
be rounding the upper level low and the left front exit region of
the jet should be over the southeast Texas Panhandle.  This upper
level divergence should combine with a cold front which should lie
from near Canadian, TX to near Wayside, TX by this time, to bring a
chance of showers and thunderstorms to much of the Texas Panhandle.
The cold front should help to lift the surface air and as the upper
level low approaches it should help out with instability aloft.
Showers and thunderstorms are expected to break out along and north
of this front.  A few thunderstorms that get going ahead of the cold
front could become severe with large hail and damaging winds the
main threats.  A tornado can not be ruled out given the lower LCL's
in the moist air and the turning of the winds with height ahead of
the cold front.  The upper level system will move away from the
Panhandles tonight and showers and thunderstorms will slowly come to
an end from west to east tonight.  Windy conditions will be found
behind the cold front late this afternoon into tonight.  At this
point, it looks like winds should stay below advisory criteria.
Highs today should range from the upper 60's northwest to the lower
80's in the east as the cold front makes its way south southeast
across the Panhandles.

LONG TERM...Thursday through next Wednesday...
Longwave trough will exit to the east to begin the long term
forecast, leading to northwesterly flow and cooler temperatures
across the CWA Thursday. A decent pressure gradient will be present,
so the north-northwesterly surface winds will likely be breezy as
well. Some hint at fire weather concerns Thursday afternoon, but
with continuing greenup and rain likely Wednesday afternoon and
evening, do not think this will end up being much of an issue.

Northwest flow in the upper levels continues for Friday, but an
850mb thermal ridge will work eastward across West Texas, extending
northward to the Panhandles. A warming trend right back up into the
mid to upper 70s will be the result.

Latest wave to potentially impact the region is progged to come
onshore over Tijuana Saturday, quickly translating northeastward
over AZ/NM by the evening hours. Southwesterly surface winds will
set up across the Panhandles as the wave approaches, with lee
cyclogenesis occurring by the late evening. The result will be a
very warm Saturday followed by a mild Sunday as guidance pushes a
cold front south through the Panhandles early in the day. Some
guidance attempts to spit out QPF during this time period, but given
the overall moisture starved thermodynamic profiles, have continued
to keep mentions of precipitation out of the forecast.

Guidance begins to diverge significantly after Sunday. Notable
solution would be the GFS, which brings an upper trough across
Monday into Tuesday, depicting rain as the disturbance drives
overrunning on top of the cold dome associated with the cold front
from Sunday. While a handful of GEFS members are roughly on board
with this solution, the EC/CMC are not. Additionally, nearly
every system fitting into this pattern over the past several
months has underachieved, sometimes in dramatic fashion. Have thus
held PoPs to a slight chance or less.

Ferguson

AVIATION...06Z TAFs...
A cold front will push through the TAF sites before noon. North
winds will increase into the 20 to 25 knot range with higher gusts
in the afternoon. Thunderstorms will be possible at the AMA site
during the afternoon and evening as an upper level storm system
moves across. Gusty winds and hail will be possible with the
strongest storms. Believe at this point, DHT and GUY will remain
thunderstorm free. Skies are expected to remain VFR at all sites,
except local MVFR conditions will be possible with the
thunderstorms.

&&

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

&&

98/16/3

Hazardous Weather Outlook
National Weather Service Amarillo TX
330 AM CDT Wed Apr 17 2019

OKZ001>003-TXZ001>020-317-172100-
Cimarron-Texas-Beaver-Dallam-Sherman-Hansford-Ochiltree-Lipscomb-
Hartley-Moore-Hutchinson-Roberts-Hemphill-Oldham-Potter-Carson-
Gray-Wheeler-Deaf Smith-Randall-Armstrong-Donley-Collingsworth-
Palo Duro Canyon-
330 AM CDT Wed Apr 17 2019

This Hazardous Weather Outlook is for the Texas and Oklahoma
Panhandles.

.DAY ONE...Today and Tonight.

Thunderstorms are expected Wednesday afternoon and evening. Some
storms could become strong to severe, with severe storms most
likely across the eastern Panhandles. Large hail, damaging winds,
and heavy rains, possibly leading to localized flooding will all
be possible. Additionally, an isolated tornado cannot be ruled
out.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

There is a slight chance for thunderstorms Monday night and
Monday. The threat for severe weather with these storms appears
minimal at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed after 1pm this afternoon.

Special Weather Statement
National Weather Service Amarillo TX
145 PM CDT Wed Apr 17 2019

TXZ019-171915-
Donley TX-
145 PM CDT Wed Apr 17 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN DONLEY COUNTY UNTIL
215 PM CDT...

At 145 PM CDT, Doppler radar was tracking a strong thunderstorm near
Clarendon, moving northeast at 30 mph.

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

Locations impacted include...
Clarendon, Howardwick and Greenbelt Lake.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Take shelter in a sturdy building if threatening weather approaches.

&&

A Severe Thunderstorm Watch remains in effect until 800 PM CDT for
the Panhandle of Texas.

LAT...LON 3483 10099 3489 10108 3514 10091 3509 10067
TIME...MOT...LOC 1845Z 209DEG 25KT 3495 10096

Ward

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