Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 271740
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1240 PM CDT Mon Mar 27 2017

.AVIATION...

For the 18Z TAFs:

VFR conditions will prevail through this afternoon and evening.
Later tonight after midnight MVFR conditions should impact the
terminals through the remainder of this valid TAF period. There
will also be a chance for rain during the morning hours that
could impact visibilities. At this time only mention of MVFR
ceilings are given, but several things could change between now
and tomorrow morning. Models have been in pretty good agreement
for precipitation, and there is the small chance some
thunderstorms could develop as well which would possibly create
some gusty conditions. Look for more refined details in the next
couple sets of TAFs.

Guerrero

&&

.PREV DISCUSSION... /Issued 619 AM CDT Mon Mar 27 2017/

AVIATION...
For the 12z TAFs...
Light northwest and west surface winds will briefly become light
and variable, and then become light southeast and south this
afternoon.  Southeast surface winds increase a bit this evening
as surface high pressure ridge departs to the east.  This will
result in low-level moisture return, with the threat for MVFR or
IFR ceilings beginning around 24 hours from now, just at the end
of this forecast.  Until then, VFR conditions expected with only
high- or possibly brief mid-level clouds anticipated.

Cockrell

PREV DISCUSSION... /Issued 420 AM CDT Mon Mar 27 2017/

DISCUSSION...
A fairly pleasant start to the work week, but we will see changes
quickly as thunderstorm chances encompass the Panhandles Tuesday.

Brief upper level ridging and winds shifting back out of the south
will help us recover nicely with highs in the 70s area wide. The
surface pressure gradient across the western Panhandles will tighten
in response to a lee side low this afternoon which could result in
breezy winds this evening.

Main focus of the forecast remains on the potential for severe
weather Tuesday and Tuesday night. An upper level low is progged to
approach the Panhandles late Monday night/early Tuesday morning.
As the low traverses the southern Rockies the orientation will
transition from positively tilted to neutral before becoming
negatively tilted by Tuesday afternoon. As the low undergoes its
orientation shift, southeasterly low level flow will bring a warm
front northwards and an ample supply of Gulf moisture with it into
the Panhandles. A Pacific front will also set up across the
southwestern Texas Panhandle then southwards to the Big Bend. As
the low center moves over the Panhandles Tuesday evening/night the
Pacific front will push eastwards into western Oklahoma. The low
is then progged to slowly move across the Panhandles over the
course of the day on Wednesday before exiting during the day
Thursday.

While thunderstorm chances look good across the Panhandles
Tuesday/Tuesday night, there are a few factors which could affect
the severity of expected storms. First, let`s talk about one
factor which could greatly limit the severity of storms; morning
convection. The morning convection depicted in nearly every model
could greatly slow the northward progression of the warm front.
Should the warm front stay further south than expected, then the
higher end of the severe threat would shift south with it as the
triple point would also be further south and we would have even
less instability.

Now that we`ve got that out of the way; here are a few factors
which could promote severe weather chances. 1) The past few model
runs have show a northward track trend of the upper low. This
could be a course correction from earlier runs which took the low
track much further south. Regardless, a further north track of the
low as it nears the Panhandles could increase our severe chances
as we would have the triple point squarely over the area, and
would see a lower duration of morning convection. 2) Deep layer
shear (0-6KM) of 60 to 70kt, curved hodographs, and MU CAPE of
1000-2000 J/kg would promote healthy rotating updrafts. 3)
Forecast PWATS across the off-Caprock counties of around 1" and
on-Caprock counties of 1/2" to 3/4" from west to east respectively
could also present the possibility of heavy downpours with storms
that develop. This threat could be reduced by storm motions of 35
to 40kt. 4) Low-level helicity maximizes along the warm frontal
boundary during the evening of 200-400 m^2/s^2 across the
southeastern Texas Panhandle; of course this assumes the warm
front makes it that far north.

Overall, we are looking the potential for severe storms
Tuesday/Tuesday night. The main hazards at this time are hail
up to the size of ping pong balls, and damaging wind gusts of 65
MPH. If the morning convection has minimal impact on the northward
progression of the warm front then an isolated tornado can not be
ruled out during the evening primarily for the southeastern Texas
Panhandle.

While we will also have the potential for thunderstorms on
Wednesday as the upper low continues to move across the
Panhandles, we will be lacking sufficient instability for severe
weather. We will dry out on the back side of the system Thursday
and Friday before the next upper low moves towards the area for
the weekend. Medium range models have a widespread on surface low
placement for this system which will affect the strength and
coverage for storms.

&&

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

&&

$$


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