Area Forecast Discussion
Issued by NWS Amarillo, TX

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505
FXUS64 KAMA 191123
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
623 AM CDT Sat May 19 2018

.AVIATION...12Z TAFs...A complicated set of TAFs for all
terminals, as low CIG and thunderstorm chances are possible. The
highest confidence for TSRA/VCTS was represented with either
PROB30 or prevailing conditions, with northerly winds increasing
to 15 to 30 kts as a cold front surges south BTWN 19/21Z thru
20/00Z. Post-frontal stratus is possible, with such a deck already
present at KDHT, which could bring IFR/MVFR CIGs to all terminals
AFT 20/05Z. It is possible that the stratus deck at KDHT could
clear shortly after sunrise. Given all the uncertainties
concerning frontal/dryline position and whether thunderstorms will
occur near or over terminals, TAF amendments are quite likely
during the forecast period.

Bieda

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                89  52  72  56  78 /  20  40  20  30  30
Beaver OK                  87  54  75  54  84 /  20  40  10  20  30
Boise City OK              80  46  72  52  80 /  20  20   5  20  20
Borger TX                  90  54  74  58  82 /  20  40  10  30  30
Boys Ranch TX              89  53  73  56  81 /  10  30  10  30  30
Canyon TX                  90  52  71  56  79 /  10  40  20  30  30
Clarendon TX               91  56  73  58  79 /  20  60  20  30  20
Dalhart TX                 85  48  72  53  80 /  20  20   5  30  30
Guymon OK                  84  50  74  54  82 /  20  30   5  20  30
Hereford TX                90  52  72  54  78 /  10  30  20  30  30
Lipscomb TX                90  55  75  55  82 /  20  50  20  20  30
Pampa TX                   88  52  72  57  80 /  20  50  10  30  30
Shamrock TX                91  58  75  58  81 /  20  60  20  20  30
Wellington TX              94  60  75  60  82 /  20  70  30  30  30

&&

.PREV DISCUSSION... /Issued 337 AM CDT Sat May 19 2018/

DISCUSSION...
A weak surface low is evident on the surface analysis this morning
centered around Potter County. A cold front is also analyzed
progressing southward across the western Panhandles, with a
dryline situated across the southwestern Texas Panhandle near
Bootleg. These features will play an important role with today`s
weather pattern, as thunderstorm development is expected to occur
this afternoon and persist into the evening and overnight hours.
The main focus for the strongest convective activity will be south of
the cold front, and to the east of a dryline. Based upon the
latest output guidance from the HRRR, HRRRX, NAM3 and the Texas
Tech WRF model, convective initiation is likely to occur around 3
to 5 PM CDT this afternoon. Pinpointing the exact location will be
greatly dependent upon the southward progression of the existing
cold front. The HRRR supports the front advancing far enough
across the region that only the southeastern Texas Panhandle could
see the strongest thunderstorms with severe potential. The TTU
WRF, however, supports the front retreating far enough north to
place the southern half of the Texas Panhandle in a region of
favorable convective initiation. Regardless of the solution,
though, additional thunderstorm activity is possible behind the
frontal boundary with thunderstorms possibly moving east/southeast
off the high terrain of New Mexico and Colorado into the northern
Panhandles.

As a result of all the aforementioned factors, the Storm
Prediction Center has requested a special sounding for 19Z this
afternoon to help assess the environmental potential. The best
educated guess given forecasted environmental parameters is that
development will occur in an environment with 1500 to 2500 J/kg of
MLCAPE this afternoon ahead of the frontal boundary. Shear is
much more favorable than has been in prior events, with a
reasonably hooked hodograph supportive of right moving supercells
and 30-40 kts of 0-6 km bulk shear. Low level veering of the
winds, especially if low level jet support can make it into the
southern Texas Panhandle, could bring a brief window of tornado
potential around 4 to 7 PM CDT. However, given the explosive
potential of convective initiation, the main hazards may evolve
from discrete supercells (hail and tornado threat) to clusters of
thunderstorms possibly congealing into a line (damaging wind
threat) this evening. By early Sunday morning, a reinforcing push
will help the cold front to clear the region reducing
thunderstorm chances early Sunday morning.

On Sunday, temperatures will be quite reasonable for this time of
year as daytime highs stay in the lower to mid 70s areawide.
Southeasterly flow is expected to return to the region with a
shortwave trough passing overhead. This could bring another round
of showers and thunderstorms, though activity should be much more
tame in the presence of cloudy skies across the area limiting
overall instability. Through the remainder of the forecast
period, model guidance diverges considerably enough that it is
difficult to pinpoint any day that could see higher concerns for
severe weather. There is a chance for thunderstorm activity
through Friday, as the region stays under southwesterly flow aloft
with upper lows digging into the western United States. The
dryline is expected to slosh back and forth across the combined
Panhandles, with the best precipitation chances expected to exist
east of it during the rest of the forecast period. A gradual
warming trend is also forecast starting Monday, with highs
reaching back into the upper 80s and lower 90s by Thursday.

Bieda

&&

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

&&

$$

98



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