Area Forecast Discussion
Issued by NWS Amarillo, TX

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239
FXUS64 KAMA 300420 AAB
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
1120 PM CDT WED JUN 29 2016

.Aviation...
For the 06Z TAFS...VFR conditions are expected to prevail through the
period at all TAF sites, though possibly MVFR visibilities could
accompany any thunderstorms that develop tonight or again Thursday
afternoon. Possibility for storms to impact TAF sites through around
08Z tonight, then another round of storms expected to develop across
the OK Panhandle and northwest TX Panhandle after 20Z on Thursday.
Given uncertainty in coverage of storms, currently only have mention
of TSRA with a PROB30 group at KGUY and left mention out of KDHT and
KAMA for now. Otherwise, gusty southerly winds are expected through
the day on Thursday.

NF

&&

.Prev Discussion... /Issued 604 PM CDT WED JUN 29 2016/

Aviation...
VFR conditions expected to prevail for the majority of the 00z TAF
cycle minus brief periods when convection impacts the terminals
directly. An outflow boundary is currently closing in on the KAMA
terminal which could spark a storm near the KAMA terminal around the
start of the 00Z TAF while KDHT and KGUY remain convection free for
the first several hours of this TAF cycle. Have inserted a PROB30
group for KDHT and KGUY for a second round of convection expected to
move into the between 10 and 14Z. Have not inserted mention for KAMA
as there is some question how fast the storms will move southward
across the Panhandles. Surface wind gusts will increase into the 20
to 25kt range during the late morning and early afternoon hours.

Prev Discussion... /Issued 413 PM CDT WED JUN 29 2016/

Short Term...This Afternoon through Friday Night...A ridge of high
pressure is presently located over the four corners region of the
desert southwest, placing the combined Panhandles under northwesterly
flow. Convective development over our area this afternoon has not
materialized as subsidence behind a passing shortwave trough
prevents any convection from taking hold. Subsidence should gradually
decrease this evening as another shortwave trough located over
northern Colorado, along with a developing lee side low over
southeastern Colorado, aid in continued thunderstorm formation over
the higher terrain of Colorado and New Mexico. Organization of these
thunderstorms off the Rockies of Colorado may occur leading to
another forward propagating MCS that progresses southeast through
eastern Colorado and southwestern Kansas late tonight. The MCS, and
any outflow that propagates from it, will have MUCAPE of 1000 to 1500
J/kg to interact with in the Oklahoma & far northern Texas Panhandles
which may help sustain it`s forward progression. Increasing
southwesterly flow over the western and southwestern portions of the
combined Panhandles due to the aforementioned lee side low will bring
in slightly drier air, which may preclude any convective activity
starting or making it to that region. Have opted to keep mention of
thunderstorms for the northern and eastern portions of the combined
Panhandles to handle this potential, and will monitor downstream
potential to see if convection can propagate further west than
presently forecasted.

On Thursday, the ridge over the desert southwest is progged to
weaken and move southeast into western Texas. Height decreases across
the combined Panhandles, along with increasing frontogenesis along
the quasi-stationary boundary, low level theta-e ridging, and
moderate isentropic ascent should all combine to provide a favorable
environment for convective initiation. Diabatic heating through the
day Thursday will contribute to a moderately unstable environment,
with MLCAPE approaching 1500 J/kg.  Storm motion through the day
will also be fairly slow, with east to northeast motion along and to
the south of the boundary of 15 to 20 kts. Should any storms become
right movers, this motion will be slower still at roughly 10 kts.
Therefore, the other concern with these storms will be heavy
rainfall in an environment with around 1.25 to 1.50 inches of PWV.

On Friday, the ridge will be located over central Texas presenting a
more southwesterly to westerly flow over the combined Panhandles. A quasi-
stationary frontal boundary will still be present across the
northern and northeastern portions of the combined Panhandles though
it will become more diffuse through the day in a moist environment.
Strong isentropic lift along this boundary, PWV values around 1.25 to
1.50 inches, and weak diffluence aloft due to a passing shortwave may
support another round of thunderstorms through the day on Friday
mainly over the Oklahoma Panhandle and northern Texas Panhandle. Bulk
shear in the convective environment will be forecasted to be slightly
higher at 25 to 30 kts, with higher values just north of the CWA.

Bieda

Long Term...Saturday through Tuesday Night...An upper level short
wave is projected to move through Colorado and New Mexico on
Saturday morning and make it to the Oklahoma and Texas Panhandles by
Saturday evening. At the surface, the stationary front should start
moving eastward through during the morning hours and shift southerly
winds at the surface to the north. As this feature approaches and
moves through the area, showers and thunderstorms will likely impact
our area. Maximum temperatures should be near the upper 80s in the
far northwestern portions of the Oklahoma and Texas Panhandles, and
be closer to the upper 90s in the far southeastern portions of the
Texas Panhandle. Elsewhere, temperatures should stay in the mid 90s.

Once the upper level short wave moves past the area late in the day
on Sunday, upper level ridging should begin to build in from the
northwest and return the Texas and Oklahoma Panhandles to
northwesterly flow aloft. Overnight, winds should transition to a
more southerly direction for Monday. Around this time in the
forecast, the models begin to disagree some as the ECMWF goes with a
more zonal flow aloft whereas the GFS keeps the area under more
amplified ridge and more meridional flow. This difference will result
in contrasting solutions regarding precipitation as the ECMWF has
more rain forecast than the GFS. For now have decided to go with a
blended consensus due to continued disagreements between modeling
solutions, and have included lower end chances for precipitation.

Tuesday is a bit tricky as the ECMWF has an embedded shortwave
moving through the Oklahoma and Texas Panhandles while the GFS has
the feature further north and moving through portions of Nebraska.
Both solutions bring an increased chance for rain Tuesday evening
and overnight, the only difference is timing and location. For now,
have kept a slight chance for rain in the central and eastern
portions of the area. Temperatures will gradually get warmer through
the weekend and early parts of next week with high temperatures on
Tuesday reaching the upper 90`s and approaching the century mark in
the far southeastern portions of the Texas Panhandle.

Lorenzen

Aviation...Previous Discussion...18Z TAF Cycle...An upper high over
the four corners region will build slowly east through 18Z Thursday.
VFR conditions are expected at all three TAF sites through the TAF
forecast period. A frontal boundary across southwest Kansas along
with a northwesterly upper flow across the Panhandles will contribute
to possible convection later today and this evening at the Amarillo
TAF site. Will include a Tempo Group from around 23Z today to around
03Z Thursday or so. Another convective complex is expected to push
south and east across the northern Panhandles later tonight and
Thursday morning, similar to late last night and this morning, and
will include a Tempo Group for convection at both the Dalhart and
Guymon TAF sites between about 10Z to 14Z Thursday for this
possibility. Southwest to south winds should back around to the south
and southeast after 00Z Thursday 5 to 15 knots.

Schneider

&&

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

&&

$$

6/99



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