Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 241727

Area Forecast Discussion
National Weather Service Amarillo TX
1227 PM CDT Mon Sep 24 2018


VFR conditions expected at all TAF sites through the period. Main
issue will be the wind shift associated with a frontal boundary
that will push southward through the period and the timing of this
shift at each terminal. Regardless of the exact timing, expect an
eventual shift to very gusty winds out of the northwest by the
end of the TAF period.



PREV DISCUSSION... /Issued 408 AM CDT Mon Sep 24 2018/

Early morning low clouds and fog over eastern parts of the Texas and
Oklahoma Panhandles will dissipate by mid to late morning.  No
precipitation is expected today or tonight. Surface low pressure
trof over eastern New Mexico will be overtaken in northern
sections by a weak cold front moving into the western half of the
Oklahoma Panhandle this afternoon. This frontal boundary is not
expected to move much this evening, but to begin moving south late
tonight. High temperatures today will be on the warm side as
south and southwest winds prevail. Southwest 850 mb winds expected
to remain in the 25 to 35 kt range overnight ahead of incoming
cold front. Drier air with these winds should preclude a repeat of
early morning low clouds and fog.


The main focus continues to be on Tuesday`s cold front which will
support much cooler conditions Tuesday and Wednesday along with
showers and a few thunderstorms Tuesday night into Wednesday
morning. The latest satellite obs reveal an open wave upper level
trough moving across the Great Basin towards the central and
northern Plains. As this system shifts east across the plains
today into tomorrow an associated cold front will push through the
Panhandles. Confidence has increased some on the overall timing
of the front (it should be through Amarillo by noon). However,
temperatures are going to be tricky as there may be some lag for
the better CAA and cloud cover behind the front. There is also
some possibility for compressional heating along and just ahead of
the front given modest density differences between airmasses.
Moreover, went coolest in the northern half of the FA but expect
70s to perhaps even 80s in the far southern FA before the CAA
arrives resulting in a non-diurnal trend (Slightly modified NMM
seemed to capture this pretty well). Also, given decent CAA and
associated low level jet, expect a few hours of north winds around
25 mph late Tuesday morning through Tuesday afternoon. Some gusts
approaching 40 mph is certainly possible, especially for areas on
the Caprock. The initial passage of the front should be dry,
however, some very brief drizzle can`t be ruled out along the
front during Tuesday morning in the northeast FA where the low
level moisture looks better.

The interesting part of this equation is the latest model trends
to shift post-frontal precip into the southern Texas Panhandle
mainly Tuesday night into Wednesday morning. Several models and
model ensembles are now suggest areas along and south of I-40 may
get some rain during this time as a secondary upper trough axis
shifts southeast over the southern Rockies and leading mid- level
shortwave with associated speed max ejects out of central New
Mexico. The combination of modest 500mb cooling (from -6 deg C to -12
deg C) and some decent PVA will help saturate the 700mb to 300mb
levels ahead of the main trough axis, but the best low level
moisture will have pushed into the southern Texas Panhandle and
Lubbock`s FA. The combination of shortwave dynamics, upslope flow
behind the cold front and modest 700mb theta-E advection ahead of
baroclinic zone at that level will support the development of
showers, and given periods of elevated instability, isolated
thunderstorms are also possible. Heavy rain could lead to some
localized flooding, but hail and wind are not expected to be a
threat. There are still plenty of things that could go wrong for
precip development in the southern Texas Panhandle such as 1)
front pushes low level moisture too far south, 2) 700mb theta-E
advection and baroclinicity isn`t as strong as advertised, or 3)
shortwave timing/location is off. Thus, kept precip chances
limited to high end chance for now.

Much drier air should invade late Wednesday as trough axis finally
crosses and northwest flow takes over aloft. Cloud cover will
decrease from north to south going into Wednesday evening, with
highs only reaching into the 60s for most of the area. A few
showers may linger in the southeast Texas Panhandle Wednesday
afternoon, but any precip accumulations should be mostly over
with by that time. Zonal flow takes over Thursday with a dry and
warming trend through the weekend as we head back into the 80s. It
doesn`t look like another cold front will approach the area until
at least early next week.



.AMA Watches/Warnings/Advisories...



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