Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 261128 AAA
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
628 AM CDT SUN JUN 26 2016

.Aviation...
The fog at DHT with MVFR conditions should be short lived, so have
not inserted it into this forecast. Otherwise, VFR conditions should
prevail outside of thunderstorms at all sites through this forecast.
The best chance of thunderstorms will be this evening, so have
inserted a PROB30 at all sites during this timeframe. Winds will be
light and variable for the first part of the forecast, then they
should become southeast, but they should remain around 10 knots or
less.

&&

.Prev Discussion... /Issued 347 AM CDT SUN JUN 26 2016/

Discussion...
Thunderstorms formed last evening in a fairly narrow corridor near
asurface trough that extended from northeast New Mexico into
Kansas. This boundary probably had some tie to northern Plains
shortwave butbaroclinicity along the boundary was weak or non-
existent in analysis earlier in the day prior to convective
development. Thunderstorms became fairly numerous during the evening
before diminishing later in the night. Cold pool/mesohigh and
outflow has masked this boundary making it diffuse and recovery from
this tomorrow is in question. Models vary in surface pressure
pattern depiction tomorrow with most not showing a synoptic scale
boundary and several showing an increasingly difluent surface wind
field during the afternoon. For this reason, have limited
precipitation probabilities to the high end of chance category
during the afternoon and evening. Despite lack of a noteable low
level convergent signal in short term guidance, thermodynamics
support convective development with moist low-levels in an
uncapped environment that will become increasingly unstable as
heating commences. Weak forcing for ascent may be present on the
northern edge of an upper low that will drift slowly east-northeast
into central Texas tomorrow afternoon. Highest precipitation
probabilities were aligned with model placement of strongest pressure
gradient on 1.5 PVU surface, but trends will be monitored and
adjustments to this will be made based on observational data through
the day.

Relatively weak mid level lapse rates should limit MLCAPE to
around 1,000-1,500 J/kg this afternoon. Winds aloft continue to be
weak with 0-6 km shear around or under 10 knots and cloud layer
shear around 15 knots at best. This is insufficient
for sustained/organized updrafts and will limit the severe potential
to isolated brief marginally severe gusts. Slow storm movement and
deep moisture (model projected PWAT around or slightly over 1.5")
will support locally heavy rainfall amounts. We saw this today with
1.68 inches measured at the Eva mesosnet.

Similar thermodynamics Monday along with subtle height falls by
evening from deepening Great Lakes trough should be enough to justify
high chance probabilities once again. There is some questionon
placement and degree of amplication of western of southwestern CONUS
trough though and this could ultimately be further east/stronger
leading to reduced chances. The ridge should build in substantially
enough Tuesday to limit chances to slight/low across most of the
area.

Mid-upper level flow will increase and veer to northwesterly by
late Tuesday. This persists through at least the end of the week
with periodic shortwaves embedded within the flow affecting the
area. When and exactly where these enhance convective development
is uncertain, although models are in agreement on a fairly
pronounced shortwave passing by Wednesday, possibly resulting in an
MCS that may affect the northeastern portion of the forecast area
Wednesday evening. We have confined highest probabilities then to
those areas.

Late Thursday through Friday evening may be when the highest
chances for precipitation exist. Models shift or reorient the upper
ridge further south which results in west-northwesterly flow over
our area and a series of perturbations pass through. These along
with mountain diurnal convection and overall faster mid level
flow suggest an organized thunderstorm complex or two may pass
through during that period, especially across the northern half of
the area. A weak cold front may move southward into the area then
too bringing slightly cooler temperatures late in the week and into
the weekend.

BRB

&&

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

&&

$$

15/17


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