Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 231756
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1256 PM CDT Mon May 23 2022

.AVIATION...18Z TAFS...
Terminals may start off at VFR in the first couple hours, but
conditions will diminish and persist in the IFR to possible LIFR
category by 00z. Storms are expected to initiate in the western
Panhandles between 21-00z. This time is low confidence and
therefore if storms develop on the earlier side then amendments
will be needed at the TAF sites. The initial round of storms will
have the potential to be severe with hail being the main threat.
After 00z the storms will start to transition more to rain showers
with isolated thunder possible. In general, there could be very
long lived times at all sites (more favorable at KAMA/KGUY) that
lightning could be occurring. But as we go to a more stable
precipitation it`s more likely to have moderate to heavy rain, and
isolated thunder. In general, after 00z, expect IFR/LIFR cigs,
rain showers with isolated to scattered thunderstorms, and winds
around 10-15kts out of the east southeast.

Weber

&&

.PREV DISCUSSION... /Issued 338 AM CDT Mon May 23 2022/

SHORT TERM...Today through Tuesday Night...

Our best shot at widespread beneficial rainfall in some time arrives
late this afternoon into tonight. Additionally, as is typical for
our springtime rain events, this comes with a risk for severe
thunderstorms and, while widespread flooding is quite unlikely given
lack of antecedent rainfall, flooding in urbanized areas is possible
if heaviest showers manage to track directly over developed areas.
While noting that light rain and/or drizzle could occur over a large
portion of the area this morning through Tuesday night, risks for
impactful weather will focus on three times and spaces:

1) Severe thunderstorms in the south central and southeastern TX
Panhandle from midday Monday through Monday evening, with a large
hail risk.

2) Severe thunderstorms in the far western TX Panhandle late Monday
afternoon into Monday evening, with a risk for large hail and
damaging winds, in that order, and perhaps a tornado.

3) An areawide risk for urbanized flooding Monday evening into
early Tuesday morning.

For meteorological details and reasoning, continue reading below.

08z WV satellite reveals cyclonic flow over the CONUS with a notable
upper wave over UT, a wave over LA, and southwesterly flow aloft
over the Panhandles with multiple perturbations seen upstream over
NM, far W TX, and the Mexican Plateau. At the surface, high pressure
is present over the upper Midwest, with the southern extent of this
ridge subtly extending southward into E TX in the wake of the LA
wave. On the SW edge of the surface high, upslope southeasterly
winds are in place across the Panhandles and, with dewpoints in the
40s and 50s to our southeast, low level moisture has been slowly but
surely increasing overnight. Given the subtle southward bulge in the
surface ridge in E TX, richest return flow remains generally
confined to south TX, where dewpoints in the 60s are seen, with this
moisture beginning to advance northwestward to the Concho Valley as
of the current hour.

Today, as the UT upper wave translates over CO and a jet streak on
the westward side of this feature overspreads AZ/NM, lee troughing
is expected to develop in E NM. With the Midwest surface high
building eastward over the Great Lakes, upslope southeasterly low
level flow will continue in the Panhandles. Given depth of progged
moisture, the continued low level upslope flow, and associated
mostly cloudy to overcast conditions today, current thinking is that
the dryline that will develop to our west will struggle to mix
eastward. Have thus gone with highs closer to consensus MOS values,
undercutting NBM by several degrees in most locations. Additionally,
the location and strength of ongoing surface stabilization will be
paramount to determining thunderstorm location and potential risks
with any thunderstorms.

As 850mb theta-e advection ramps up around midday, first potential
risk for severe thunderstorms enters the forecast across an area
bounded within both the southern half and eastern two thirds of the
Panhandles, with the most bullish guidance suggesting progged MUCAPE
of 1000-1500 J/kg. Model soundings suggest a stabilized surface
layer, reasonable given expected cloud cover, with potentially
unstable parcels being lifted from 750-800mb. Shear magnitude above
this level is modest and profiles reveal straight hodographs, so am
not expecting much in the way convective organization with anything
that develops here. However, with midlevel lapse rates of 8 C/km
beginning to overspread the area, cannot rule out severe hail with
any thunderstorms. Given weak effective shear and expected lack of
rotating updrafts, hail risk will largely be dependent on buoyancy
alone, with this suggesting a risk for perhaps stones up to 1.5"
diameter. Moderate surface stabilization suggests very little risk
for damaging winds and precludes a risk for tornadoes. With 850mb
moist advection continuing, this risk for elevated thunderstorms
with perhaps severe hail will remain through the evening hours until
a cold front crashes southward.

Shifting focus to the far western TX Panhandle, while the dryline is
expected to struggle to mix eastward, southwesterly 700mb flow looks
to potentially lead to a reduction in sky cover during the
afternoon. As this occurs, the richest moisture, currently located
near the Concho Valley as described above, will surge northward,
perhaps reaching our CWA and opening the door for surface-based
instability, with around 1500 J/kg of MLCAPE potentially developing
before a shortwave approaches from west during the late afternoon.
Given 0-6km bulk shear of around 40 knots oriented roughly
orthogonal to the dryline, initial discrete development is possible,
although very short hodographs above 2km suggest convection may
struggle to take hold. Should convection develop and maintain
itself, aforementioned shear and steep mid-level lapse rates suggest
a risk for large hail, perhaps up to 2 inches in diameter. Lack of
surface stabilization suggests a risk for severe gusts but, with
cloud bases generally much lower than typical given robust moist
advection, top end potential is muted. Finally, given those lower
cloud bases - progged LCLs are generally below 7000 feet - and low
level turning in shear profiles with surface to 500m SRH around 50
to 100 m2/s2, a stray tornado cannot be ruled out during the short
window in which convection, should it maintain itself, remains
discrete. As western TX Panhandle convection grows upscale and
shifts eastward, surface based instability will be lost and risks
will transition as it moves to the decidedly hail-focused risk zone
described in the previous paragraph.

Moving ahead to Monday night into early Tuesday, a cold front pushes
southward into our moisture rich airmass. As this occurs, UT upper
wave approaches. With both large scale upper support for modest lift
and a stronger lower level lifting mechanism present in the form of
the front, widespread showers with some thunderstorms are expected
to develop. With pre-convective PWAT of around 1 inch, some moderate
rain could occur with slow storm motions of around 15 to 20 knots
allowing areas to receive close to the full potential of rainfall.
Given our drought status, soils should largely absorb this with ease
but, due to those slow storm motions, urbanized areas may see some
flooding issues should a heavier shower or thunderstorm pass over
these localized paved areas.

Later on Tuesday, cool and cloudy conditions are expected in the
wake of the front. With the upper wave slowly moving eastward over
the area, additional light rain could occur largely via isentropic
lift over the cold dome. Additional urban flooding risk appears
minimal as post-frontal isentropic upglide tends to produce
middling amounts of precip in the Panhandles and this event looks
to be no exception.

Ferguson

LONG TERM...Wednesday through Sunday

Closed upper low over the central Plains states Wednesday will
lift east and north away from the Panhandles through Thursday.
Subsidence behind the departing upper low and upper ridge building
in over the U.S. Rockies mid to late week will allow for drier and
warmer condition leading up to the upcoming weekend. Upper ridge
tracks east late this week and this weekend and breaks down as a
northern stream closed upper low and West Coast upper trough moves
east over the weekend. Upper flow across the Panhandles becomes
southwesterly on Saturday as the closed upper tracks east and
south onto the West Coast late in the weekend.

Surface high builds in over the Panhandles Wednesday but then
quickly exits the forecast area by Wednesday night. Lee surface
low and trough develop and deepen during the latter half of this
week with the surface pressure gradient tightening up across the
Panhandles. Breezy to windy conditions expected by Thursday
afternoon through Friday with the surface trough/dryline tracking
east into the western half of the Panhandles by Saturday
afternoon. Medium range models have differing solutions to the
cold front expected to impact the forecast area late in the
weekend. The GFS attempts to bring the front into the Texas
Panhandle late Saturday before the frontal boundary retreats back
to the north by Sunday. The GFS then brings the cold front through
the forecast area Sunday night into Monday. The ECMWF solution
brings the cold front into the Panhandles by 12Z Sunday and then
stalls the front across the extreme southeastern parts of the
forecast area into eastern New Mexico by 00Z Monday before lifting
the frontal boundary back to the north again Sunday night. Lots of
uncertainties this far out in the forecast period.

Schneider

FIRE WEATHER...

Friday and Saturday...

Lots of uncertainties and low confidence with regards to the ERC
percentiles on Friday and Saturday and how the rainfall early
this week will impact or not impact the fuels. Despite this
unknown factor, elevated fire weather conditions may be possible
on Friday as the 20 foot winds increase out of the south and
southwest 15 to 25 mph with higher gusts and minimum afternoon
relative humidities are forecast to be as low as 11 to 13 percent
Friday afternoon. Max RFTI values on Friday are forecast to be as
high as 1 to 3 across most of the Panhandles.

For Saturday, critical fire weather conditions may be possible
across the western half of the area from Texas County in the
Oklahoma Panhandle to Carson and Armstrong Counties in the Texas
Panhandle westward to the New Mexico state line. Max RFTI values
are forecast to be as high as 4 to 7 across the western half of
the Panhandles with minimum afternoon relative humidity values on
Saturday as low as 8 to 10 percent. 20 foot southwesterly
downsloping winds are expected to increase to around 15 to 25 mph
or as high as 20 to 30 mph with higher gusts.

Schneider

&&

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

&&

$$

89/99


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