Area Forecast Discussion
Issued by NWS Amarillo, TX

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000
FXUS64 KAMA 220422
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1122 PM CDT SAT MAY 21 2016

.Update...
Made minor adjustments to precipitation chances overnight based on
trends in New Mexico. Eastward shifting ridge and mid-level height
falls impinging on the area may be enough for convection to sustain
overnight. There is a consistent signal in CAM guidance of elevated
convection later tonight, particularly across the southeast Texas
Panhandle where Bufkit RAP and NAM soundings show deepening low
level moisture. Original thinking was that mid level capping on 00z
KAMA sounding may remain atop moistening boundary layer limiting
elevated convective potential overnight, but this may be less of a
factor further west as is evidence by recent trends in eastern New
Mexico. MUCAPE of 1,000-2,000 J/KG may support a marginally severe
hail threat if storms sustain/redevelop. Also made adjustments to
temperatures given upper 60 degree dew points now advecting into the
southeast Panhandle. This raises concern for some advection fog later
tonight as well in addition to the low stratus.

BRB

&&

.Aviation... /For the 06z TAFs/
Elevated convection may increase across the western and southern
Panhandles tonight. Probabilities of either of the three terminals
being impacted are relatively low, with Dalhart and Amarillo having
the best chance. A significant surge of low level moisture is
occurring on southeasterly winds. Obs in the eastern Panhandle show
upper 60 degree dew points already. As this advects northwestward and
temperatures cool, there is growing likelihood of fog later tonight
particularly at Amarillo and Guymon. MVFR or IFR conditions may
develop by around 09z and continue until mid morning. Thereafter, VFR
conditions will return but thunderstorms should redevelop during the
afternoon and persist into the evening. Gusty southeast winds will
continue for the rest of the TAF period.

BRB

&&

.Prev Discussion... /Issued 335 PM CDT SAT MAY 21 2016/

Discussion...
Thunderstorms that develop this afternoon across the western
Panhandles will move east this evening with at least a marginally
severe wind/hail threat persisting through late evening.
Deepening moisture and increasing precipitable water values per
short term guidance and trends in the upstream GPS PWAT sites,
combined with relatively slow storm motions are supportive of
locally heavy rainfall amounts and possibly flooding potential,
particularly later this evening in the southern Texas Panhandle. For
specifics on convective initiation and potential severe please see
the previously issued mesoscale discussion. Updates on mesoscale
evolution will be sent as needed through the afternoon and evening.

There is a decent signal in some of the models of warm/moist
advection process keeping convection going across the southern
portion of the Texas Panhandle through the night. Most of the
forecast soundings still show evidence of ridging/subsidence for
most of the night, but the eastward progression of the ridge may be
enough for some activity late especially in the southeast Texas
Panhandle where the WAA signal is maximized. Kept low probabilities
to account for this mainly focused on the southeastern Texas
Panhandle.

Modest ascent will overspread the area tomorrow in diffluent upper
flow regime. A sharpening dryline across the western Panhandles
should focus thunderstorm development during the afternoon in a
moderately unstable environment with MLCAPE of 2,000-2,500 J/KG. 0-6
km bulk shear of around 30 to 40 knots should be sufficient for
storm organization and supercells. Large hail and damaging winds
will be the primary threat although with relatively low LCL heights
generally less than 1,000m isolated tornadoes will be possible. The
best chance for a tornado would be during the evening as low level
jet strengthens causing low level shear to increase and before
significant boundary layer stabilization occurs.

Troughing to our west continues through mid-week before accelerating
eastward toward the Panhandles by the end of the week. Until then
mid-level momentum should allow the dryline to mix/sharpen across
the far eastern Panahandles and this convection should be limited to
this area. We will need to monitor trends in the short term guidance
as the time nears in case models are mixing the dryline too far east
as has been the case lately. This is a more synoptically active
scenario with fairly decent cross-boundary mean flow, thus the
reasoning for not adjusting westward at this time. If models trend
slower and more amplified with approaching truogh, we will likely
need to introduce at least low probabilities of convection in the
east portion of the Panhandles.

BRB

&&

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

&&

$$

3/14


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