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fxus64 kama 211807 

Area forecast discussion
National Weather Service Amarillo Texas
107 PM CDT Wed Aug 21 2019


18z taf cycle:

Main concerns this taf cycle will be the higher potential
for thunderstorms mainly this evening between 23z and 09z. Kguy
and kdht have the highest probability of being impacted so have
included tempo groups to try to pinpoint the most likely timing.
Kama could still be impacted, but confidence is lower so have
opted for prob30 group there. Storms could produce strong outflow
winds, small hail and heavy rain (local MVFR cigs/vsbys).
Otherwise, VFR conditions are generally expected. A weak cold
front will also be moving into the kguy vicinity this afternoon
and evening before eventually pushing through the rest of the area
overnight (most likely augmented by thunderstorm outflow). Thus,
a wind shift can be expected overnight, but winds should be less
than 10 knots after 06z then gradually shift back to the southwest
towards 18z Thursday.



Previous discussion... /issued 634 am CDT Wed Aug 21 2019/

Aviation...12z tafs...

VFR conditions expected to be predominant through the taf period.
A few lingering showers associated with a deck of clouds at or
around 10000 feet possible near the terminals early this morning
main concern for this issuance is the potential for showers and
thunderstorms and all sites this afternoon and evening. Best
chance is at dht and Guy after 23z and 22z this afternoon,
respectively. Have covered the 6 most likely hours with a prob30
group. With Ama having a lower probability, with a peak
probability later in the taf period, did not mention thunder with
this issuance. Additionally, a cold front may push south through
Guy this evening, giving winds a more northerly component.


Previous discussion... /issued 416 am CDT Wed Aug 21 2019/


Short through tonight

Current look at observational data shows a weak surface trough to
our west across far NE nm, a cold front positioned roughly along
the Kansas/NE border, scattered thunderstorms across Kansas and a growing
mesoscale convective system across NE, and a series of upper perturbations from northern
Utah eastward toward the NE Panhandle. 500mb ridge over the Southern
Plains has begun to decrease in intensity and elongate in the east-west

With cross barrier flow continuing to our northwest, should have
another day with downslope southwesterly winds at the surface, so
highs in the upper 90s and a few triple digits are expected once
again. Guidance in good agreement that a wave will break across the
mountains this afternoon into this evening, with thunderstorms
developing along the Sangre de Cristos and the weak surface trough
across NE nm pushing east toward the panhandles. While moisture in
the lower levels will continue to be a limiting factor, moist 700mb
moisture advection looks to set up ahead of this wave, giving US a
bit more moisture to work with than previous days. Combined with the
more impressive forcing via the aforementioned wave, should have
more widespread showers and thunderstorms across the County Warning Area compared to
previous days. Additionally, thunderstorm development may focus
along the Kansas/NE cold front mentioned above should it reach the
Oklahoma Panhandle. While most guidance depicts this feature
stalling to our north, the rap/NAM/namnest do bring it all the way
south. This seems plausible given enhancement from the outflow from
thunderstorms ongoing across NE. Have thus distributed likely pops
across our west and northwest, where forcing ahead of the wave will
be greatest, and across the OK Panhandle in deference to the
potential approach of the cold front.

As for potential hazards, flooding risk is low due to the dry lower
levels - pre-convective naefs precipitable water values are near average for this
time of year. Given those dry lower levels however, dcape should
once again be notable, with progged values of 750-1500 j/kg seen.
Damaging winds will thus once again be a potential hazard. As for
hail, given progged afternoon MLCAPE of only 500-1000 j/kg and 0-6km
bulk shear of 15 knots or less, do not think hail will be much of a
concern aside from a very marginal threat in our northwest due to
cooling temperatures aloft ahead of the wave.


Long term...Thursday through Wednesday

The frontal boundary is expected to stall Thursday across Oklahoma
and then back to the west and south across either the southern
Texas Panhandle or portions of the Texas South Plains region.
Convection chances will continue Thursday through Friday as the
upper high builds across the southwestern states and Four Corners
region late this week and shortwave troughs track southeast out of
the central and southern rockies and across the panhandles. With
the frontal boundary stalled across the southern Texas Panhandle
across southern Oklahoma or the Red River valley, chances for
mainly afternoon and nighttime convection will continue through
the end of the week. Drier conditions expected this weekend as the
frontal boundary tracks a little further south and the upper high
begins to build back to the east again by late in the weekend and
early next week. The upper high builds in over the panhandles
next Monday and Tuesday allowing for a return to the hot weather
once again. The upper high then expected to build further east
away from the forecast area by the middle of next week with mainly
afternoon and nighttime convection chances returning by next
Wednesday. A cold front is expected to move south and east across the
panhandles by the mid to late afternoon hours next Wednesday. This
cold front will have better cold air advection behind it and should
move through the forecast area rather quickly. Max temps next
Wednesday will be mainly in the 80s.



Ama watches/warnings/advisories...


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