Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 231125
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
625 AM CDT Fri Apr 23 2021

.AVIATION...
VFR conditions expected at all TAF sites as we go past 13-15Z
this morning. Currently, IFR cigs at KAMA, IFR cigs with FG at
KDHT; with a TEMPO group at KDHT for the first hour due to FG and
VFR cigs at KGUY to start the TAF period. Winds will pick up this
afternoon out of the SW then veering to NW by 21-23Z for KDHT
/KGUY as a cold front moves through. Cold front timing will be
around 00-02Z for KAMA. Winds will be around 10-20 kts with higher
gusts at times.

Meccariello

&&

.PREV DISCUSSION... /Issued 343 AM CDT Fri Apr 23 2021/

SHORT TERM...Today through Tomorrow Night...

Watching closely the chance for thunderstorms this afternoon and
this evening, especially across the eastern Panhandles where a few
storms could be severe.

Current observations early this morning indicate the main H500
positive tilted trough axis just about over the Four Corners
region as it continues to move east. Over the Panhandles this
morning, portions of the central and eastern Panhandles are
experiencing rather extensive low cloud cover. This supports ample
low level moisture over most of the region currently. As a matter
of fact, Td values as high as the upper 40s can be seen as far
west as eastern New Mexico this morning. Further to the southeast
over the Texas Hill Country, Td`s this morning are already in the
upper 50s to lower 60s. In this persistent south and southeast
surface flow, especially as it increases this afternoon, some of
the latest hi-res numerical data brings these higher dewpoints
into portions of the eastern Panhandles later today. The main
broad surface low, now centered in the vicinity of Union/Quay
County, NM will move ESE throughout the morning hours into the
Panhandles and be centered near Palo Duro Canyon later this
afternoon. Along the surface, a trailing cold front to the west
and a warm front to the east/northeast will differentiate the
stable vs conditionally unstable airmass.

Going into the afternoon hours, a dryline out of eastern NM will
move east in the wake of the departing surface low as it continues
to move southeast towards northwest Texas. Further to the
northeast and east of the surface low, the dryline to the west
will help to steepen the main H850-700 theta-e advection north and
north-northwestward over the warm front and in a cyclonic flow
around the surface low. This will provide suitable instability
with MLCAPE values approaching 2500-3000 J/kg in some of the high
res model data in the SE TX Panhandle being in the warm sector.
Although sfc-1 km shear is not that impressive of average around
10-15 kts, a bit better if you average sfc-3 km shear of around 40
kts, thanks to the H850 jet. In combination with the previous
elements, especially areas closest to the dryline and near the
better moisture transport axis wrapping around the now slow moving
surface low, discrete and/or transient supercells may develop in
the warm sector across the south central and southeastern Texas
Panhandle with some activity also possible in the northeastern
Panhandles, as long as cloud cover can diminish. Large scale
ascent w.r.t the placement of the H500 jet will also support
vertical growth in the column. If thunderstorms develop this far
west into the eastern Panhandles (with the better ingredients
further to the east in western Oklahoma), large hail and damaging
winds will be possible with these thunderstorms. Also cannot rule
out a tornado with some model data indicating sub 800m LCL
environment in the warm sector across the far southeastern TX
Panhandle. Storm mode should quickly become more a linear cluster
if enough cells develop and move quickly to the east as the shear
magnitude in the lower veering profile is not the strongest with
winds being the main threat later into the evening hours.

Have to also mention that if low clouds hang tough, this could
limit surface initiation holding a prompt cap in place. Some
23/00Z model and numerical data also displaces main moisture
transport well to our east keeping our area dry. Storms could also
develop in the far east and quickly move out into western
Oklahoma with not much precipitation in the Panhandles. Will be
monitoring observational trends carefully to see the setup of the main
storm activity going forward.

Along the now neutrally tilted H500 trough axis with a rather
impressive PVA strip moving through Panhandles this evening,
storms that develop across the high terrain of NM/CO will move
into the northwestern Panhandles tonight. These storms will not
likely be severe as they move into a more stable environment. The
last of any shower or storm will exit the Panhandles around
midnight.

Zonal flow returns to the region tomorrow with dry conditions and
high temperatures in the 70s.

Meccariello

FIRE WEATHER...

Elevated fire weather conditions will be possible this afternoon,
especially ahead of a passing cold front for the southwest Texas
Panhandle. Min RH values will be as low as 10 percent with 20 ft
winds out of the west at 15 to 20 MPH. Max RFTI values will be 2
to 3 with ERC percentile in the 70th to 80th.

Meccariello

LONG TERM...Sunday through Thursday...

The latest model output continues to support much warmer
conditions along with increasing downslope winds Sunday into
Monday. This will occur as the upper level pattern amplifies in
response to a digging western NOAM trough while ridging builds
over the ArkLaTex to OH Valley region. A belt of westerlies aloft
will increase over the area Sunday with an increasing south
component by late afternoon. This setup will encourage lee surface
troughing as a low level thermal ridge expands over NM and west
TX. Southwest winds of 20 to 30 mph will be common Sunday and
Monday, which will help mix down the very warm 850mb temperatures
of 25 to 28 degrees C. The latest guidance has slightly warmer
850mb temperatures on Sunday, which should help boost temperatures
into the upper 80s to low 90s across the area. Monday has a bit
more model variance with 850mb temps which may be due to increased
high level cloud cover. That said, current forecast highs are
mainly in the mid to upper 80s Monday with stronger wind fields
that will result in a higher fire weather threat compared to
Sunday (see more in the Fire Wx Discussion below).

The deterministic models and ensemble members are in even less
agreement for how to handle the western NOAM upper trough as it
advances east across the Rocky Mountains Tuesday through Wednesday.
The EC and CMC are in general agreement with a slower progression
of the wave as a closed low forms over the Desert Southwest. The
00z CMC evolution was most favorable for what would be the best
potential for active weather late Tuesday and Wednesday across the
Panhandles as a dryline sets up in the area. The 00z EC was
slightly weaker, further north, and more progressive with a
dryline setting up near the western OK state line. The GFS is
sticking to its typical very progressive solution, completely dry
slotting the Panhandles - however several GEFS members are more
in line with the slower EC/CMC. Bottom line for now is that
Tuesday will probably be dealing with some combination of fire
weather west of a dryline and potentially severe weather to the
east, but the jury is out on where the dryline will setup. A cold
front will eventually make it down late Tuesday or Wednesday,
which is when the best precip chances are currently advertised
with the blended solution (NBM).

Ward

FIRE WEATHER...Sunday through Thursday...

Elevated to critical fire weather conditions are expected over
portions of the Panhandles just about each afternoon, Sunday
through Thursday. Sunday and Monday are most favored (highest
confidence) for critical fire weather across most of the combined
Panhandles, with Tuesday being more uncertain but possibly more
concerning as well. Starting Sunday, an anomalous low level
thermal ridge will be positioned over the Panhandles combined with
mainly pressure gradient driven downslope surface winds. There
will be some enhancement of the southwesterlies aloft (especially
on Monday), but there are no notable jet streaks or stacked jets
prior to Tuesday. This will help mitigate wind gusts some despite
strong mixing, but sustained twenty foot winds of 20 to 30 mph
will be possible. High temperatures near 90 degrees on both Sunday
and Monday will lead to min RH values in the single digits in the
west, to teens in the east (this may be mitigated by high clouds
Monday). RFTI values of 4 to 6 should be common (locally higher),
and the latest ERCs suggest 70th percentile and higher are
already occurring (despite areas still appearing to be green
around Amarillo). Will take ERCs at face value given our recent
freezes and lack of any meaningful precipitation over the last 3
to 4 weeks. This of course could change for any areas that get
precipitation as a system crosses the area tomorrow.

Tuesday into Wednesday will see potential for better
alignment of stronger jet streaks as the upper disturbance
crosses, but fire weather potential will depend on position of a
dryline and timing of a cold front with possible loss of the warm
temperatures / low level thermal ridge. There is still a lot of
model variance with this time frame and it will need to be watched
closely.

Ward

&&

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

&&

$$

29/7


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