Areal Flood Advisory 2, NWS Amarillo, TX

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
551 PM CST Sat Mar 13 2021

.AVIATION...
For the 00Z TAFs, showers and tstms will be east of the KAMA terminal
site by 01Z. Otherwise, no precipitation is expected during this
fcst cycle. Residual low clouds should erode as drier air invades
the region from the west. Southwest winds will increase and become
gusty by mid morning Sunday as the pressure gradient tightens.

02

&&

.PREV DISCUSSION... /Issued 343 PM CST Sat Mar 13 2021/

MESOSCALE UPDATE...This Afternoon and Tonight.

..Severe Weather Outbreak expected This Afternoon and Evening...

* Synoptic Overview: An H5 upper low around 549 dm is approaching
  the 4 corners areas this afternoon. Preceding this feature is a
  120 to 140 kt jet at the H25 level that splits in two. One part
  is headed towards Colorado while the other part is aimed at the
  southeastern Texas Panhandle. This does mean that the left jet
  exit region will be over the Texas and Oklahoma Panhandles
  through the course of the day and aid in convective development,
  whether elevated or surface based. As the upper level low
  progresses east, it is anticipated that the associated trof
  pattern will take on a negative tilt aiding in evacuation of
  mass via diffluence aloft.

* Mesoscale: Multiple features of note today include a
  stationary/warm front, a sharpening dryline in eastern New
  Mexico and a developing cold front just behind the dryline in
  eastern New Mexico. The stationary/warm front has been slow to
  lift northward, though has now pushed north and northwest into
  all but the but the Oklahoma Panhandle and Dallam and Sherman
  Counties in the northwestern Texas Panhandle. The warm
  front/stationary boundary could potentially surge north ahead of
  incoming thunderstorm activity from New Mexico. The thunderstorm
  line is coincident with the nose of the H5 jet and will continue
  to push east into the Texas and Oklahoma Panhandles. Meanwhile,
  the dryline will continue to sharpen and push east south of the
  warm front/stationary boundary, but could be quickly overtaken
  by the developing cold front later this afternoon and evening.
  As the cold front surges east, a stronger jet pushing off the
  Rockies could cause the thunderstorm to establish bowing
  segments along the line. The warm, moist sector will have an
  hour or two of clearing ahead of the thunderstorm line owing to
  passing cirrus deck, with upper 50s to lower 60s dew point
  temperatures. The thermodynamic parameters are all supportive of
  severe weather today with MUCAPE around 1000-1500 J/kg in the
  cold sector of the northwest, and 1000-2000 J/kg in the
  warm/moist sector south of the stationary frontal boundary.
  Shear is not in question, as effective bulk shear has increased
  into the 70 to 80 kt range, and 0-500m helicity has been
  increasing to 100 to 300 m2/s2 range through the afternoon.
  Given moisture profile ahead of line segment, it is expected
  that individual supercell formation will occur with LCLs quite
  low to the ground around 500 meters.

* Threats: All hazards are in play, including the potential for
  large hail possibly greater than 2 inches, wind gusts
  approaching 70 to 80 mph, tornadoes that could be long-lived and
  long-tracked, and flash flooding due to the available moisture
  in the region. All thunderstorms that form will be moving
  quickly, around 50 to 60 MPH towards the northeast. Should the
  storms turn right, they should slow down to around 40 to 50 MPH
  but still move quickly.

* Timing & Location: The best region for the most intense
  supercell thunderstorms are east of a line representing I-27 and
  US Highway 87/287 north of Amarillo, or essentially encompassing
  the eastern 2/3 of the region. The entire Texas and Oklahoma
  Panhandles can anticipate that any thunderstorms in the region
  could be severe, and those that enter the eastern 2/3 of the
  region could be capable of producing the strongest of all severe
  weather hazards.

* Summary: A strong upper level low situated over the 4 corners of
  the desert southwest will be pushing through a dryline/Pacific
  Cold Front through the afternoon. The potential exists for a
  severe weather outbreak with the possibility of large hail
  possibly exceeding 2 inches, wind gusts up to 80 MPH, and
  tornadoes that could be large and long-lived (especially in the
  eastern 2/3 of the Texas and Oklahoma Panhandles).

HYDROLOGY...This Afternoon and Evening.
Even though storm movement is on the order of 40 to 50 mph, rather
high PWATs and some training of storms will likely pose a threat
of flash flooding this afternoon and evening, especially eastern
half of the TX Panhandle where deeper moisture currently resides.
The greatest threat for flash flooding will exist from late this
afternoon into early this evening. This threat will diminish by
late this evening as the main precipitation shield moves bodily
into Oklahoma.

02

LONG TERM...Sunday through Saturday.
Very busy day so will keep this short. The strong upper level low
pressure system causing the severe weather today and this evening
will slowly move into southeast CO by late Sunday afternoon, then
across southern KS Sunday night. This will place our forecast
area in the dry slot region of this storm along with gusty
southwest winds. Dry weather is expected Monday and Monday night.
Another upper level low pressure system is then slated to impact
the region Tuesday afternoon through Wednesday. Based on the
latest models projected path, northern zones will have the
greatest chance for receiving more precipitation, with overall
lowest threat in the southern TX Panhandle. Dry weather returns to
the region Wednesday night through Saturday. Utilized NBM pops and
temperatures Sunday through Saturday.

02

&&

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

&&

Hazardous Weather Outlook...UPDATED
National Weather Service Amarillo TX
636 PM CST Sat Mar 13 2021

OKZ001>003-TXZ001>020-317-141100-
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-
636 PM CST Sat Mar 13 2021

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

.DAY ONE...Tonight.

Thunderstorms are expected to continue through this evening across
mainly the eastern half of the Oklahoma and Texas Panhandles.
Some storms will become severe, with large hail, damaging winds,
tornadoes, and flash flooding all possible. A Tornado Watch
remains in effect for the eastern half of the Texas Panhandle
until 9 PM CST.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is likely through mid evening.

02

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