Special Weather Statement, NWS Amarillo, TX

Area Forecast Discussion
National Weather Service Amarillo TX
403 PM CDT Wed Jul 26 2017

.DISCUSSION...
Not a lot of changes in this forecast compared to the previous.
Fairly broad mid/upper level high pressure spinning over TX/NM.
Winds aloft will be weak and vary from west to north depending on
smaller scale waves coming off the Rockies. A cold front is being
sampled with most of the cooler air up in northern KS over to the
Front Range. However, a surface low is positioned over north-
central KS which has helped switch winds to the north over the OK
Panhandle along with a weak baroclinic zone. Isolated
Thunderstorms are beginning to develop along this boundary. A
surface trough is situated roughly over the Canadian River Valley
where scattered CU and a few towering CU are trying to break a
weak cap. Any activity that does develop south of the boundary
should be isolated single cell, short lived thunderstorms with
some downburst potential given steep low level lapse rates,
moderate instability and downdraft CAPE on the order of 1000-1500
J/kg. Warm 500mb temperatures should keep hail growth minimal.

Thunderstorm chances go up considerably this evening and overnight
as a shortwave develops off the Rockies on the northern periphery
of the high pressure. Model guidance shifts this wave eastward
with most of the PVA across the northern zones. The frontal
boundary will be the focus for enhanced moisture convergence with
pos low level theta-E advection coming in behind the front. PWAT
values are expected to increase to 1.5 to 2.0 inches with surface
dew points increasing well into the mid to upper 60s along the
boundary. CAMs and medium range guidance have been consistent with
initiating a large area of thunderstorms across the northwestern
zones where the best forcing along the boundary combine with the
mid level forcing from the shortwave. Due to the high PWATs, weak
mid level flow and shear vectors oriented parallel to the
boundary, storms should be efficient heavy rain producers. Have
issued a flash flood watch for the far northwestern TX Panhandle
and far western OK Panhandle for the overnight and early morning
period. Severe potential overnight looks low as storms become
elevated and loose maximum buoyancy potential (MLCAPE values drop
to around 1000 J/kg given low mid level lapse rates) and weak
shear. Can't completely rule out some severe downburst winds
become strong enough to break the surface inversion, but it seems
unlikely as the surface inversion is progged to be fairly strong.

The overnight convection may congeal into an MCS and slowly move
southeast until the forcing from the upper level shortwave shifts
east of the area. This should lead to possible lull in activity
Thursday morning after 12z as the convection becomes less
organized and coverage decreases. Their are some differences in
model guidance on how far south the surface boundary will push,
with medium range guidance keeping it stalled over the northern
zones. However, short term guidance (NAMNest and NMM/ARW) suggest
this boundary may push as far south as the I40 corridor. This
seems plausible given overnight storm cold pools should help
advance the boundary south. Thus, shifted higher chance pops south
covering most of the southern Panhandles. There is not a clear
indication of a shortwave, but convergence along the boundary and
the very moist vertical profiles will lead to at least scattered
thunderstorm development. Storms should continue to be efficient
rain producers with similar environmental conditions to Wednesday
night so will need to watch for flooding potential.

Rain chances will continue through the extended as statistical and
deterministic guidance keeps moisture in place, especially across
the eastern zones. The upper level high isn't progged to move
much until later next week when models do suggest that it will
shift westward leaving the Panhandles in more dominant northwest
flow. Still, occasional shortwaves and the existence of lingering
boundaries will keep chance pops through the next 7 days.
Temperatures will also stay much closer to average, if not
slightly below average beyond the day 1 forecast.

Ward

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                69  89  67  91  68 /  40  40  40  20  30
Beaver OK                  73  86  68  89  68 /  40  50  40  40  40
Boise City OK              65  79  64  85  64 /  80  50  40  40  40
Borger TX                  73  91  71  93  71 /  40  40  40  30  40
Boys Ranch TX              71  90  69  92  69 /  50  40  40  20  30
Canyon TX                  69  90  68  92  68 /  30  40  40  20  20
Clarendon TX               71  93  69  92  70 /  20  40  30  20  30
Dalhart TX                 70  85  66  89  66 /  70  40  40  30  30
Guymon OK                  70  82  67  88  67 /  60  50  40  40  40
Hereford TX                70  91  68  93  67 /  40  40  40  20  20
Lipscomb TX                74  90  70  91  69 /  40  30  40  40  40
Pampa TX                   70  90  68  91  68 /  40  40  40  30  40
Shamrock TX                73  95  71  92  71 /  30  40  30  30  40
Wellington TX              73  98  72  95  72 /  20  40  30  20  30

&&

.AMA Watches/Warnings/Advisories...
TX...Flash Flood Watch from 9 PM CDT this evening through Thursday
     morning for the following zones: Dallam...Hartley.

OK...Flash Flood Watch from 9 PM CDT this evening through Thursday
     morning for the following zones: Cimarron.

&&

98/7

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Special Weather Statement
National Weather Service Amarillo TX
357 PM CDT WED JUL 26 2017

OKZ003-262130-
Beaver OK-
357 PM CDT WED JUL 26 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN BEAVER COUNTY UNTIL
430 PM CDT...

At 357 PM CDT, Doppler radar was tracking a strong thunderstorm over
Bryans Corner, or 15 miles north of Perryton, moving east at 10 mph.

Wind gusts up to 50 mph will be possible with this storm.

Locations impacted include...
Bryans Corner, Balko and Boyd.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3652 10058 3651 10091 3667 10096 3668 10095
      3678 10065
TIME...MOT...LOC 2057Z 257DEG 11KT 3662 10084

Bieda

Special Weather Statement
National Weather Service Amarillo TX
411 PM CDT WED JUL 26 2017

TXZ006-011-012-262145-
Hartley TX-Potter TX-Oldham TX-
411 PM CDT WED JUL 26 2017

...SIGNIFICANT WEATHER ADVISORY FOR EASTERN OLDHAM...WEST CENTRAL
POTTER AND SOUTHEASTERN HARTLEY COUNTIES UNTIL 445 PM CDT...

At 411 PM CDT, Doppler radar was tracking strong thunderstorms
extending from 12 miles west of Boys Ranch to 9 miles north of Vega.
Movement was northeast at 15 mph.

Wind gusts up to 50 mph will be possible with these storms.

Locations impacted include...
Channing and Boys Ranch.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3578 10231 3541 10209 3528 10240 3552 10255
TIME...MOT...LOC 2111Z 229DEG 11KT 3549 10248 3538 10241

Bieda