Severe Thunderstorm Warning 239, NWS Amarillo, TX

Area Forecast Discussion
National Weather Service Amarillo TX
635 PM CDT Thu Jun 13 2019

.AVIATION...00z TAFS...
VFR conditions expected at all TAF sites. Thunderstorms will be
possible in the 0-6z time frame, with the expectation that any
remain storms should be east of the terminals by 06z. Cigs will
increase coverage with initial heights around 20kft AGL, given
the thunderstorm anvils. Thereafter, expect any thunderstorm bases
to be around 6kft AGL. Winds will still be breezy out of the south
in the 15-20kt range gusting 25-30kts through about 10z. Low level
jet will set up and there will be a period of WS in the TAFS from
the overnight time through about 12z. Small chance of storms in
the 18z-00z time period, but that will be refined with later TAF
packages.

Weber

&&

.PREV DISCUSSION... /Issued 256 PM CDT Thu Jun 13 2019/

SHORT TERM...Tonight and Friday...
Forecast is still on track for anticipated thunderstorms later
today. Severe weather is expected to develop and impact the
Panhandles through the evening hours. At least one or two supercells
will be possible before storm mode becomes more cluster/linear. Main
threats will be damaging wind gusts of 60-70 mph, hail upwards near
2.00", and possible flash flooding due to slow storm mode and high
rainfall rates around 1"/hr coupled with already saturated soils.

We are currently tracking a subtle but potentially potent shortwave
that is noteably in both upper air charts and water vapor. Watching
for the timing of this with an expected surface trough for storm
initiation and evolution. Breezy southerly flow is expected today
which will aid in strong theta-e advection along the western fringe
of the forecast area given our forecast dew points. We could easily
hit 1500-2000 J/kg MLCAPE this afternoon along western parts of the
forecast area where thunderstorms should initiate. RAP is
forecasting 40-50 knots of effective shear, which is likely to
produce strong rotating updrafts in at least a couple thunderstorms.
Supercell storm mode will be anticipated early on before the upper
level wave pushes east and likely makes a scenario more favorable
for cluster type mode. Low level helicity values are impressive
after 7pm, but LCL heights will likely be too high for a tornado
threat in any supercell. This is something in particular we need to
monitor closely, especially if storms go more linear as quick spin-
ups are possible in the lower LCL height environment. AS activity
pushes east we should start to see a decrease in threats, especially
after midnight.

Thunderstorms will exit the region by early Friday morning.
Thunderstorms are possible Friday by this is very conditional and we
may end up being convection free through the afternoon hours. That
said, tomorrow is going to be our warmest day of the year as
widespread 90 degree temperatures are anticipated. The Palo Duro
Canyon may very well hit 100-105, so any Canyon goers should be
prepared for hot conditions.

LONG TERM...Friday Night through Wednesday Night...
Westerly flow aloft will continue.  Right now it looks like the
dryline will mix somewhere near the Amarillo area, with strong
capping east of the dryline.  Subtle shortwave to the north may
allow for storms to trigger along the northeast OK Panhandle.
Otherwise, best chance of storms will be along the dryline where the
convergence is strongest.  Models not putting out too much QPF and
soundings indicate that it still may be just capped enough to limit
storm development.  (Still will not rule out isolated storms east of
the dryline, so for now going with 20 pops, against a drier
guidance.)

Saturday flow aloft will become more southwesterly as weakly
amplified trof will pass through the Panhandles.  ML CAPE values are
off the charts in the afternoon, in the 3000-4500 J/kg range.
Certainly will be a chance of storms, and storms that develop will
be severe on Saturday.  There is the potential for very large hail
(Baseball or larger)and strong damaging winds. LCL's will be pretty
high across the southern Panhandles, but will drop off below 1000m
across the OK Panhandle in the evening.  This will increase the
tornado threat. There is the chance that the southern Panhandles
will be dry-slotted as the thermal ridge sets up just over the area.
So the focus for the severe weather at this time would be north of
the I-40 corridor, and east of Amarillo.

Cooler air will be in place on the back side of the wave as a lee
surface high sets up over eastern CO.  Surface flow will start off
out of the north and become easterly on Sunday, as another surface
high dives down from Canada and lingers over northeast NE.  This
will help advect surface dewpoints back into the 60s, while weak mid
level flow out of the west and northwest will help bring Pacific
moisture to the area.  ML CAPE values in the 1000-2000 J/kg range
will open up the potential for strong to severe storms again on
Sunday. Models want to trigger storms off the mountains, in
association with subtle mid level wave's moving through.  Best
chances of storms will be across the west.

The same flow regime is expected to continue on Monday and Tuesday
providing more round of storms to the Panhandles. Dryline may mix
enough east on Tuesday to keep the southwestern Panhandles dry.  But
there is some uncertainty.

As we move into Wednesday northwest flow still looks to prevail, but
drier air in the mid levels will help to shut down the thunderstorm
chances, as well as the dryline expected to mix to the central
Panhandles, possibly as far east as the OK state line.

Weber

&&

.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX                61  94  65  92  60 /  40  10   5  10  20
Beaver OK                  60  93  62  89  60 /  30  10  20  20  40
Boise City OK              57  93  57  84  55 /  50  10  10  40  40
Borger TX                  62  96  65  92  62 /  50  10   5  20  30
Boys Ranch TX              62  97  62  92  60 /  40  10   5  20  30
Canyon TX                  61  96  64  94  60 /  40  10   5   5  10
Clarendon TX               62  93  68  94  63 /  50  10   5   0  20
Dalhart TX                 58  94  57  87  56 /  40  10   5  20  30
Guymon OK                  60  93  59  87  58 /  40  10  10  30  50
Hereford TX                63  97  63  95  60 /  30  10   5   5  10
Lipscomb TX                61  93  66  92  62 /  40  10  10  20  40
Pampa TX                   60  92  65  91  61 /  50  10   5  10  30
Shamrock TX                61  91  68  95  65 /  50  10  10   5  30
Wellington TX              63  93  70  97  66 /  40  10  10   5  30

&&

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

&&

89/24/89

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