Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 271357
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
857 AM CDT Thu Jul 27 2017

.UPDATE...A surface low pressure area is located over northern
Oklahoma and southern Kansas this morning, with associated cold
front across all but the far southeastern Texas Panhandle. Latest
12Z sounding out of KAMA shows that despite the passage of this
front, wind fields remain light and variable from the surface to
H7 and backing with height from H7 to H2. The latter profile still
shows winds around 5 to 15 kts, with ongoing convective activity
now decoupled from upper level support presently located east of
the area.

It is expected that ongoing shower and thunderstorm activity
should gradually decrease in intensity through the morning hours,
and will need to monitor to determine if MCS activity from this
morning over southeast CO and the NW combined Panhandles left
behind a remnant MCV. If one exists, this feature along with weak
vort max wrapping around the west side of the high near our
region, may serve as another focal point for shower and
thunderstorm development through the day. PWV values around an
inch and a quarter to an inch and a half, combined with slow
movement of any storms that development, will mean that heavy
downpours may potentially cause flash flooding. Will continue to
monitor observations through the day and determine if ongoing
flash flood watch needs to be adjusted. Updated grid package has
been sent, with the remainder of the forecast still on track.

Bieda

&&

.PREV DISCUSSION... /Issued 600 AM CDT Thu Jul 27 2017/

AVIATION...
12Z TAF Cycle

Showers and thunderstorms, some with very heavy rainfall, will
affect mainly the Dalhart and Amarillo TAF sites through 12Z
Friday. However, the Guymon TAF site should be impacted by showers
and thunderstorms between 13Z and 19Z today with low confidence on
timing after 19Z today. Therefore, will leave out any mention of
showers and thunderstorms at the Guymon TAF site past 19Z today
for now. Mainly VFR ceilings will prevail through 12Z Friday,
however MVFR ceilings can be expected in and near any showers and
thunderstorms through 12Z Friday. Light north to northeast and
east winds at all three TAF sites 5 to 15 knots or less with winds
strong and erratic in and near thunderstorms.

Schneider

PREV DISCUSSION... /Issued 428 AM CDT Thu Jul 27 2017/

DISCUSSION...
Several chances of additional rainfall will be throughout the
forecast well into next week. Going forward with some areas
already receiving good amounts of rainfall, localized flash
flooding will be the main hazard.

Not much change to the previous forecast. Current regional radar
analysis shows ongoing moderate to heavy rain at times across
portions of the western TX Panhandle. There is also the main cold
front making its way south across the TX Panhandle which will help
be the focus of some additional showers and storms later this
morning. In-conjunction with precipitation from yesterday across
the same areas in the far western Panhandles, a Flash Flood Watch
has been issued from this afternoon into early tomorrow morning
for the far western combined Panhandle counties from this
afternoon into early tomorrow morning. Latest hi-res model data
shows convection developing over the high terrain of CO/NM. With
perturbations in the mid level anti-cyclonic flow with some
localized PVA in the flow, this should carry the precipitation
into the Panhandles again this afternoon. SBCAPE of 1000-1500 J/Kg
along with forecast soundings showing some good mixing in the low
levels. This can result in some strong wind gusts with some of
the stronger diurnal convection during the afternoon hours.
Otherwise, localized flash flooding will be the main threat as
abundant surface moisture, combined with weak 850-550 hPa mean
flow indicate training storms that develop along pre-existing
boundaries and/or cold pools may produce very heavy rainfall
rates. PWAT anomalies for today will also be +3 to +4 S.D. in some
of the high-res model output indicating abundant moisture to work
with.

Going forward Friday into the weekend, a deepening meridional flow
in the eastern CONUS along with the main upper level high pressure
system shifting further to the west into New Mexico will continue
to bring more chances of showers and storms, especially in the
northern and eastern combined Panhandles as more favorable upper
level dynamics along with mid level flow advecting more
disturbances into the aforementioned areas.

Chances of precipitation do not end there. Going into next week,
as the main mid level high pressure is centered over the Great
Basin, our region will be in stronger northwesterly flow advecting
more perturbations into our region in the anti-cyclonic flow.
Some of the extended 27/00Z guidance, in particular going into
next week, sinusoidal waves in the northern stream jet digging
south out of Canada may compress the southern stream jet and
displace some areas of large domain upper level divergence over
the Panhandles. This may provide the chance of stronger
thunderstorms as we go into the middle of next week. Will continue
to watch as we are still several days out. Temperatures throughout
the forecast will remain near average for late July and early
August.

Meccariello

&&

.AMA Watches/Warnings/Advisories...
TX...Flash Flood Watch from 1 PM CDT this afternoon through Friday
     morning for the following zones: Dallam...Deaf Smith...
     Hartley...Oldham.

OK...Flash Flood Watch from 1 PM CDT this afternoon through Friday
     morning for the following zones: Cimarron.


&&

$$

98/7



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