Area Forecast Discussion
Issued by NWS Amarillo, TX

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913
FXUS64 KAMA 282305 AAA
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
605 PM CDT SAT MAY 28 2016

.Aviation...
Low clouds in the MVFR range are expected to spread across the AMA
and GUY TAF sites overnight. Cigs will improve by late morning on
Sunday into the VFR range. Thunderstorms should develop during the
afternoon on Sunday with AMA having the best chance, so have inserted
a prob 30 group there. Southeast winds will be around 10 knots
overnight, then they should veer some on Sunday and then they will
increase and get gusty by afternoon.

&&

.Prev Discussion... /Issued 347 PM CDT SAT MAY 28 2016/

Short Term....TONIGHT...Development and intensification of low-
level jet tonight may support isolated showers and thunderstorms past
the early evening hours. Have increased areal extent of pops a bit
farther east before 06z, and have introduced same into north central
and northeast sections for late night hours after 06z. Otherwise,
expect widespread cloud cover to be in place by 12z, owing to
expected strong warm air advection as depicted at 850 mb.

Cockrell

Long Term...Sunday through Friday night...An upper low over the
desert southwest will slowly move east through the day on Sunday,
placing the region under southwesterly flow. In response to the
approaching weather system, a surge of low level moisture due to a
passing warm front will move across the area before halting around
the Oklahoma & Kansas state line by Sunday afternoon. An ejecting
negatively tilted shortwave trough will aid in the development of a
lee cyclone over southeastern Colorado and strengthen the dryline
over the far western combined Panhandles. With the combined
Panhandles in a warm and moist environment, MLCAPE based upon current
forecasted temperatures should reach between 1500-2500 J/kg Sunday
afternoon, with CIN eroding by early afternoon. Effective bulk shear
varies depending on which guidance is used, but present thinking is
that it will be around 20-30 kts in the northern combined Panhandles
increasing to 35-45 kts further south. With diffluence aloft, and
strong isentropic lift along both the dryline to the west & the warm
front to the northeast, dynamics are favorable for strong to severe
thunderstorms. Storms may possibly form near the warm front in the
northeastern portions of our area with slow forward propagation.
Thunderstorms that may form along the dryline may grow upscale into a
forward propagating line, with discrete supercells ahead of it Sunday
evening. Large hail, damaging winds, heavy rainfall, and an isolated
tornado or two (primarily over southern Texas Panhandle) is possible.
As the line of storms moves across the area, a cold pool may develop
along and behind these storms transitioning the threat towards strong
winds in association with a gust front along with heavy rainfall
Sunday evening.

On Monday, the upper low is not expected to make much forward
progression across Arizona placing the region under continued
northwesterly flow. Another negatively tilted shortwave trough may
move across the area midday Monday, but dryline placement and
available instability is in question. Any convection that occurs
Sunday may leave a cold pool across the southern combined Panhandles,
with model guidance suggestive of the dryline holding along the NM/TX
stateline. Should the boundary layer recover from Sunday`s activity,
there is significant instability available east of the dryline for
convective activity. Present guidance supports 2000-3000 J/kg of
MLCAPE, but shear will be light at 20-30 kts. In addition, steering
flow is quite light with forward mean layer wind speeds supportive of
about 20 kts of forward motion. Strong to severe thunderstorms are
possible, with hail and damaging winds being the primary threats.

On Tuesday into Wednesday, the upper low is progged to remain cutoff
over Arizona keeping the region under southwesterly flow. An upper
low progressing across the far northern tier of the U.S. will help
bring northwesterly flow down the front range of the Rockies, with a
cold front moving across late Tuesday night into early Wednesday
morning. As moist southeasterly flow is progged to continue into our
area, and the dryline remaining over the NM/TX stateline, another
round of thunderstorms is possible Tuesday afternoon. Based upon
forecasted temperatures (upper 70s - lower 80s) on Tuesday, present
MLCAPE values are around 2000-3000 J/kg with about 30 to 40 kts of
bulk shear possible. This will allow the threat for large hail,
damaging winds, and possibly an isolated tornado to continue.

Wednesday should present with lingering shower and thunderstorm
activity as a cold front helps in pushing moisture southward.
Differences in model guidance places some questions as to whether the
frontal boundary will clear the Panhandles before or after max
heating. Have opted to go with the potential for the boundary to
clear the Panhandles, with high temperatures dropping down into the
lower to mid 70s.

Present model guidance shows that Thursday and Friday will be a much
quieter period as the region is on the eastern periphery of a ridge
of high pressure, with the cold front pushed against the New Mexico
Rockies. Have opted to keep out mention of precipitation due to what
looks to be dry northerly and northeasterly flow. Highs on Thursday
should be in the lower to mid 70s, recovering into the upper 70s to
lower 80s by Friday.

Bieda

Aviation...Previous Discussion...18z TAFs...
Light surface winds will trend to south and southeast as zonal mid-
level flow induces development of lee-side trof.  Expect to see some
high-based cumulus clouds this afternoon.  Low-level jet develops
overnight, strengthening before sunrise, with significant moisture
return commencing.  Warm air advection will support stratus cloud
development.  Timing of onset of MVFR ceilings remains uncertain at
this time, but this forecast calls for occurrence at or before 12z
Sunday at KAMA and KGUY.  Conditions expected to deteriorate further
beyond time frame of this forecast, with scattered to numerous
thunderstorms developing Sunday afternoon.

Cockrell

Hydrology...A strong southeasterly moisture flow will occur Sunday
and is expected to persist through about Tuesday across the combined
Panhandles. Organized thunderstorms with slow forward motion will
bring the possibility for heavy rain across the area Sunday through
Tuesday. Precipitable water values are forecasted to be between 1.25
to 1.50 inches, which would be among the highest observed for this
time of year, with forecasted soundings suggestive of efficient rain
producing thunderstorms. Any slow moving thunderstorms will place
areas that receive them under a threat of localized flooding or flash
flooding. Instances of creek and river flooding, especially over the
southeastern Texas Panhandle, is possible due to previous rainfall.

Bieda

&&

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

&&

$$

15/11



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