Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 221142 AAA
AFDAMA

Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
642 AM CDT Wed Mar 22 2017

.AVIATION...
For the 12Z TAFs, low clouds have begun to develop across parts of
the forecast area, and expect them to continue to fill in this
morning. Have continued with MVFR cigs at all terminal sites.
These MVFR cigs should slowly dissipate during the early to mid
afternoon hours, only to develop once again after 06Z Thursday.

Andrade

&&

.PREV DISCUSSION... /Issued 456 AM CDT Wed Mar 22 2017/

DISCUSSION...

Main focus will be on the upcoming severe weather event Thursday
into Thursday evening. Friday also looks to be a windy day across
the Panhandles and we may need a Wind Advisory on this day.

In the upper levels, high pressure will begin to break down as an
advancing trough over the west coast makes its way over the
intermountain west. A surface low will form across eastern
Colorado/western Kansas, and a dry line will set up around western
parts of the Panhandles or perhaps as far west as the New
Mexico/Texas border. This dryline will be our focus for convective
initiation as the boundary moves east across the Panhandles.
Instability is marginal with several models showing around 500-1000
J/kg of most unstable. Forecast sounding depict weak lapse rates
which resolves to "skinny CAPE". There is however a deep moist layer
within the atmosphere. Some places could see appreciable rainfall
rates and amounts within a small timeframe. Bulk shear (0-6km)
values are pretty strong around 50-60 knots where convection is
anticipated, so there is the element to support moderate to strong
updrafts. In the early onset of the event, I see the potential for
supercell development; however, I don`t see this lasting long. We
will be capped most of the afternoon, but by late afternoon/early
evening the cap should erode and thunderstorm activity should begin
across western parts of the Panhandles. Storms should go linear
rather quickly and sweep across the Panhandles through the evening
with thunderstorm activity likely coming to and end by 07Z,
especially severe thunderstorms. There could be some lingering
storms across our east, but I anticipate the threat for severe
weather to cease shortly after 06Z. All in all, I think this will be
mainly a wind and hail threat day. At the very early stages of the
event, there is a very small window for tornado potential with any
discrete cells that form, but I believe this treat to be very low at
this time given the strong cap and weak low level shear. Wind speeds
aloft veer little with height. In fact, wind speeds are nearly
uniform with height and parallel to the boundary which further
increases confidence storms will go linear quickly. Hail ranging
from quarter to perhaps half dollar size and winds around 60 to 70
mph will be the primary threats. Convective allowing models support
this analysis in both convective mode and timing. A few things could
change between now and Thursday like the dryline placement for
timing/initiation of storms, so the forecast should still be
monitored for potential changes, but its been pretty consistent so
overall confidence is high in this forecast.

On Friday a very strong pressure gradient will set up on the back
side of the surface low due to strong pressure rises (10mb/6hr) as
it pushes east across the Panhandles. I can see a Wind Advisory
needed on this day for strong surface winds on the order of 35 to 40
mph sustained. Some models were really agressive with the winds and
output was showing 45 to perhaps 50 mph sustained speeds at the
surface. I am not that confident at this point to go that strong.
Nevertheless, its going to be a very windy day on Friday on the back
side of the departing surface low. With rainfall anticipated, it
doesn`t appear dew points will be low enough to warrant concern for
fire weather potential at this time. In fact, fire weather potential
looks low at this time for the next several days. Sunday could be
our next potential fire weather day, mainly across southwestern
parts of the Texas Panhandle, but even then it only appears to be
marginal.

Guerrero

&&

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

&&

$$


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