Area Forecast Discussion
Issued by NWS Amarillo, TX

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132
FXUS64 KAMA 241018
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
518 AM CDT Sat Jun 24 2017

.DISCUSSION...
Showers and thunderstorms are currently ongoing generally along
and south of I-40. These storms have developed in response to a
subtle shortwave moving through the northwest flow in addition to
an area of 700mb confluence and upslope flow within the PBL.
Strong pos theta-E advection is also noted generally from H850 to
H700 along the area of confluence where elevated instability is
present on the order of 1000 J/kg. Deep layer shear vectors around
20-30 knots have kept storms from becoming severe for the most
part, with one or two exceptions where effective shear was
higher. Some training of cells is occurring as development
continues upstream. Storms are becoming less organized over time,
but will be monitoring areas for some localized flooding.

The next few days will be characterized by an upper ridge which
will keep anti-cyclonic flow over the southwestern states while a
broad upper trough over the north-central US maintains cyclonic
flow over from the northern Plains to the Atlantic coasts. The
Panhandles will be under northwest flow aloft with increasing
moisture on upslope flow below. Precipitable water values should
be above the 90 percentile for at least a few days. This
combination along with shortwaves moving through the northwest
flow will lead to chances for thunderstorms every day through at
least Monday. One thing to note with these storms is that severe
potential should be on the lower side with shear staying around 30
knots. The NAM keeps most of the instability elevated with a warm
nose feature through Sunday, with much deeper moisture overall.
Interestingly enough, the NAM does not produce nearly as much QPF
compared to the Can/ECMWF/GFS through Monday, mostly likely due to
more shower type model profiles (less instability and cooler
temps) and thus less convective feedback.

For the day saturday, storms should decrease from west to east
across the southern Texas Panhandle during the morning hours.
Winds will be shifting to the southeast as surface high pressure
moves over the Ark-La-Tex region. Short and Medium range guidance
is in good agreement that clouds will be prevalent across most of
the Panhandles through the day as moisture increases on upslope
flow. The clouds and already cool air in place will results in
well below average, if not near record low high temperatures.
Models differ greatly on temperatures owing to differences in
overall depth of moisture (thickness of clouds). Nudged towards
the cooler guidance such as NAM and CAMs. Showers and
thunderstorms will be possible again during the afternoon with
better chances late Saturday into Sunday as another shortwave
moves through the northwest flow along with some isentropic
ascent. The best chances currently are expected in the western
Panhandles where better deep moisture convergence will be along a
theta-E axis, but chances will exist across most of the area.
Cloud cover is expected to be maintained through the day Sunday,
although there are large differences between the NAM and high res
models compared to the ECMWF/GFS with depth of moisture and
temperatures. For now meeting in the middle with guidance showing
anywhere from mid 60s (which would shatter record low high temps)
to low 80s on Sunday.

Early Monday looks like more of the same as the overall upper
pattern is not expected to change much and moisture will still be
in place. There may be a lag in shower/storm activity Sunday
afternoon and evening, but storms should develop and/or move in
from the higher elevations out west late Sunday into early
Monday. It does look like surface winds will finally shift to the
southwest Monday afternoon and clouds will finally decrease
allowing us to warm up back to near normal.

For the extended... The ridge over southern AZ/NM will finally
start to dampen as deterministic guidance shows a trough try to
push down out of western Canada going into Tuesday and Wednesday.
This will result in more zonal flow over the Panhandles and
decreasing rain chances. Temperatures should also come up
considerably as H850 thermal ridge build in Wednesday into
Thursday. Did nudge above the blend for those days for highs as
850mb temperatures progged 30-34 degrees C. Also nudged low
temperatures up Tuesday and Wednesday (mainly considering strong
LLJ developing overnight).

Ward

&&

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

&&

$$

2/7



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