Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 211824 AAC
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
124 PM CDT SAT MAY 21 2016

.Mesoscale Update...
...Severe weather expected today...

* Synoptic Overview: Water vapor imagery today shows an upper-level
  low pressure system over the Pacific Northwest and evidence of
  several vorticity maxima rotating around it. One vort max rounding
  the base of the low is expected to move over the Southern High
  Plains region during this afternoon and evening. It is expected to
  enhance lift as it interacts with a developing surface trough this
  afternoon. The surface trough will extend from eastern Colorado and
  western Kansas southward into eastern New Mexico, with an
  increasingly tight moisture gradient developing along the trough by
  the evening hours. Thunderstorms (some possibly severe) are
  expected to develop along and just east of this developing dryline
  by late afternoon and move eastward through the evening.

* Mesoscale: Widespread surface dewpoints in the low to mid 60s have
  advected into the eastern and central Panhandles this morning.
  Earlier low clouds are mixing out and skies are clearing across the
  Panhandles. This will allow temps to reach the low to mid 80s
  areawide this afternoon. These will combine to see 0-1km MLCAPE
  values of 1500-2000 J/kg near the developing dryline, with greater
  but better capped values farther east towards the Oklahoma state
  line. Looking at present radar returns, a north-south fine line was
  noticed moving slowly westward through the Panhandles, marking an
  area of weak moisture and wind convergence also seen in surface
  obs. Also seen were west-east horizontal convective rolls
  developing in response to strong south winds across the area. These
  suggest that storms developing this afternoon could easily ingest
  horizontal vorticity. Model guidance indicates 0-6 km shear values
  of around 30-35 kts will develop by this evening, especially as low
  level winds back slightly during the evening hours. This suggests
  storm mode will be more multicellular though some discrete
  supercells could develop initially. A low level jet developing
  during the late evening will increase low level moisture supply and
  wind shear.

* Threats: All forms of severe will be possible today, though the
  primary threats will be large hail to around golf ball size and
  damaging wind gusts associated with shorter-lived storms and
  muticell clusters. Although the tornado threat will be low,
  increasing low level wind shear and lowering LCL heights near
  sunset could provide a narrow window for isolated tornadoes with
  ongoing storms. Localized heavy rainfall is also possible, but do
  not anticipate a widespread threat for flooding or flash flooding.

* Timing & Location: Storm initiation is most likely to occur near
  the developing dryline from eastern New Mexico into western
  portions of the Texas and Oklahoma Panhandles this afternoon.
  Convective allowing models suggest we will reach our convective
  temps around 3 pm, with storm development soon after. Storms will
  move to the northeast through the evening, though it is uncertain
  how far east storms will be able to make it after sunset. As of
  now, the far eastern Panhandles have the lowest chances to see
  severe thunderstorms this afternoon and evening.

NF/HAL

&&

.Prev Discussion... /Issued 1237 PM CDT SAT MAY 21 2016/

Aviation... /For the 18z TAFs/
VFR conditions will prevail through at least early afternoon, and
probably through early tonight. The only exception may be if a
thunderstorm directly impacts a terminal. We have narrowed down a 4-
5 hour window of the most likely time for this to happen and used
VCTS, although the convection should be somewhat scattered in nature
so we did not want to prevail thunder just yet. We will amend as
location and timing becomes more certain based on satellite and ob
trends this afternoon. Southerly low level advection of moisture
will continue tonight and may lead to an MVFR or IFR ceiling,
especially at KAMA. KGUY may also experience this. KDHT could too
but is the least likely of the three.

BRB

Prev Discussion... /Issued 445 AM CDT SAT MAY 21 2016/

Discussion...
Low clouds and patchy fog this morning across the northeastern half
of the Panhandles should lift by mid morning. Deepening surface
trough will sharpen into a dryline today across the eastern plains of
New Mexico and allow for increasing southeast to southerly winds of
15 to 25 mph with higher gusts across the forecast area. Low level
moisture will be on the increase today with 1500 to 2500 J/KG CAPE
and 0-6 km bulk shear of 30 to 40 knots suggesting organized
multicellular or possibly supercellular storm modes after 21Z today.
Main threats later today and tonight will be large hail and damaging
winds. Cannot completely rule out an isolated tornado or two
early...mainly before sunset...however better chances appear to be
Sunday afternoon and evening. Similar setup on Sunday with the
dryline becoming better organized and remaining across the eastern
plains of New Mexico or near the Texas and New Mexico state line. 0-6
km bulk shear in excess of 40 knots. Tornado threat increases Sunday
afternoon into Sunday evening mainly across the eastern half of the
forecast area...along with a continued large hail and damaging wind
threat...with supercells being the storm mode. Convection should
track east out of the Panhandles between 06Z and 12Z Monday...with a
cold front pushing south into the Panhandles between 06Z and 12Z
Monday.

Cold front forecast to become stationary over the forecast area
Monday with additional convection developing Monday afternoon into
Monday evening across the eastern portions of the Panhandles. Dryline
moves east into the forecast area Monday and Tuesday. Convection
possible mainly early Tuesday over the eastern Panhandles. Front to
lift north as a warm front into southwest Kansas Tuesday and
Wednesday before reinforcing surge of cooler air finally allows the
front to push south into the forecast area once again late next week.
Warmer and drier conditions expected after Tuesday and then only
slightly cooler conditions expected by next Thursday and Friday
following the passage of the cold front.

Schneider

&&

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

&&

$$

6/17



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