246
FXUS64 KAMA 171648 AAB
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
1148 AM CDT Tue Sep 17 2024

...New AVIATION...

.KEY MESSAGES...
Issued at 341 AM CDT Tue Sep 17 2024

Above normal temperatures will continue through Friday, trending
closer to or even slightly below normal in some locations for the
weekend.

Severe thunderstorms are possible across the western half of the
area late this afternoon and evening, and then over mainly eastern
sections of the area late Wednesday afternoon and evening. Damaging
winds and large hail will be the primary hazards both days.

Additional thunderstorms are forecast to develop Friday afternoon
through Saturday night across all of the Oklahoma and Texas Panhandles.

&&

.SHORT TERM ...
(Today through Wednesday night)
Issued at 341 AM CDT Tue Sep 17 2024

A potent upper-level trough is spinning over Nevada and California
tonight while embedded vorticies in the southwesterly flow aloft
travel northeastward across the southern and central Rockies. This
upper-level trough is forecast to take a negative tilt throughout
the day and travel northeastward toward the northern High Plains.
This will result in an initially broad lee low pressure system
sprawled across the northern High Plains that rapidly develops this
afternoon and occludes tonight. The resulting steepening of the
surface pressure gradient will result in breezy southerly winds
across the Panhandles, but especially in the northwestern half of
the Panhandles where sustained winds of 20-25 mph is expected with
gusts up to 35 mph. These southerly winds will result in modest
moisture advection through the day, and as the upper-level trough
pushes northeastward, thunderstorms will develop in eastern New
Mexico as forcing associated with the system arrives. Thunderstorms
should gradually grow into a line segment as they move northeastward
toward the Panhandles, and there will be enough wind shear to
support the maintenance of a line of thunderstorms... especially
in the northwestern half of the combined Panhandles. Questions
remain regarding how far south and east the thunderstorms will be
maintained given that the wind shear is less favorable and the
more favorable forcing will be pulled northeast along with the
track of the upper-level trough, away from the southeastern half
of the combined Panhandles. Overall, current thinking is that the
greater chance for thunderstorms will favor the northwestern
combined Panhandles with the southeastern Texas Panhandle having a
lower chance of seeing thunderstorms through tonight. There will
be a risk for strong to severe thunderstorms this afternoon and
through this evening, primarily in the northwestern half of the
CWA. Instability will be on the lower end of favorability, MLCAPE
around 500-1000 J/kg, but the combination of sufficient wind shear
(for an organized line of thunderstorms) and moderate DCAPE
values around 1000-1500 J/kg should support the risk for damaging
wind gusts... particularly if any bowing segments can develop
within the line. The risk for strong to severe thunderstorms may
continue into the evening, but thinking the risk should wane as it
moves into the southeastern half of the CWA where there will be
less favorable shear and becomes displaced from the more favorable
forcing. Nonetheless, we may see showers and thunderstorms
persist through at least a portion of the night.

Showers could linger into the early morning hours in the eastern
combined Panhandles, but should clear out for much of the morning
and early afternoon hours. A Pacific front is forecast to be
positioned in a northeast-southwest fashion across the CWA by the
mid-afternoon hours, and the development of scattered thunderstorms
along the boundary will be possible. Moisture content will likely
not be a concern given the multiple days of moisture return. Despite
mediocre mid-level lapse rates, the low-level moisture content
should help get MLCAPE values into the 1000-1500 J/kg range...
slightly higher if the NAM products are correct. Wind shear will be
favorable for multicells, or perhaps even transient supercells.
However, given that it is frontal forcing, growth into clusters or
line segments may be the more realistic solution. With all that
said, there will be a chance for these thunderstorms to become
strong to severe with damaging winds the primary threat. Can`t
entirely rule out large hail if a supercell can develop, but given
the weak mid-level lapse rates, 500mb temperatures around
-5C, and relatively moist column that suggests melting hail
 potential, thinking small hail is the most probable outcome if
 there is hail at all. Thunderstorms should move out of the
 Panhandles in the evening hours.

Vanden Bosch

&&

.LONG TERM...
(Thursday through Monday)
Issued at 341 AM CDT Tue Sep 17 2024

There will be a relative minimum in precipitation chances for the
OK and TX Panhandles on Thursday as the large scale western states
upper level trof reloads with another upper level low pressure
system progged to dig southward to around the coast of central
California 12Z Thursday. This particular feature is expected to
translate eastward to near the four corners region by early
Saturday afternoon, then head east northeast into the central
plains by Sunday afternoon. This projected track is a bit slower
than previous medium range models suggested. As this storm system
approaches the area, the chance for showers and thunderstorms is
expected to increase again, mainly Friday afternoon through
Saturday afternoon. The threat is progged to diminish from west
to east Saturday night as this particular storm system heads into
the central plains on a track north of the forecast area, with
dry weather seen for Sunday and Monday.

The latest medium range models are in better agreement with the
slower movement of the upper level low pressure system and were
accepted. Also, the NBM pops and temperatures remain plausible
and reflect the above synoptic scale reasoning. Further refinements
to the long term periods are foreseen as time gets closer and
numerical weather models converge on a more common solution with
respect to timing and track.

02

&&

.AVIATION...
(18Z TAFS)
Issued at 1143 AM CDT Tue Sep 17 2024

Thunderstorms are expected to develop over eastern New Mexico this
afternoon and then they are expected to move east across the TAF
sites late this afternoon and this evening. The greatest
confidence is at DHT for a thunderstorm, so have added a TEMPO
group there. Gusty winds will be possible with the strongest
storms. Storms should be east of the TAF sites by midnight and
skies will remain VFR for the rest of the forecast. Gusty
southerly winds this afternoon will decrease later tonight behind
the thunderstorms. Southerly winds will then pick up again at 15
to 20 knots with higher gusts by late Wednesday morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                65  93  66  96 /  50  20   0   0
Beaver OK                  64  95  65  96 /  50  10  10   0
Boise City OK              57  88  54  90 /  60   0   0   0
Borger TX                  66  98  68 100 /  50  20   0   0
Boys Ranch TX              63  93  61  95 /  60  10   0   0
Canyon TX                  63  92  63  95 /  50  20   0   0
Clarendon TX               66  94  67  96 /  30  20  20   0
Dalhart TX                 57  88  54  91 /  70   0   0   0
Guymon OK                  60  92  57  94 /  60   0   0   0
Hereford TX                63  93  63  96 /  60  10   0   0
Lipscomb TX                66  96  69  99 /  40  20  20   0
Pampa TX                   65  93  66  97 /  40  20  10   0
Shamrock TX                67  96  68  97 /  20  20  20   0
Wellington TX              68  97  69  99 /  20  20  20   0

&&

.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&

$$

SHORT TERM...52
LONG TERM....02
AVIATION...15