Area Forecast Discussion
Issued by NWS Amarillo, TX

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FXUS64 KAMA 280539
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1239 AM CDT Fri Jul 28 2017

.AVIATION...
VFR conditions will be predominant for the 06Z TAF period. Widely
scattered showers and storms will be predominant throughout the
TAF period. For the onset of precipitation, some scattered
precipitation may impact KDHT. Otherwise more showers and storms
are expected starting around 21-23Z with VCTS conditions in
particular for KDHT/KGUY through to the end of the TAF period.
Some heavier storms right over the TAF sites may provide brief
MVFR/IFR conditions with heavy rainfall and sporadic gusty winds.
Winds in general will be out of the S and SE between 5-10 kts.

&&

PREV DISCUSSION... /Issued 425 PM CDT Thu Jul 27 2017/

DISCUSSION...
Water vapor imagery continues to show broad anti-cyclonic flow
over the southern Plains today. At the surface, a clear moisture
gradient and wind shift is noted just south of the I40 corridor
with mid 60 dew points north and mid 50s south of the boundary.
The main "cold front" is stalled further north, into southern
Kansas where temperatures drop from high 80s into the 70s.

Decided to keep the Flash Flood Watch for the western Texas and
Oklahoma Panhandles through the overnight period given monsoonal
plume in the area. However, there are some uncertainties with the
coverage of thunderstorms in the western zones due to a MCV that
developed in response to last nights MCS as sampled by vis sat.
Thunderstorms are developing along the eastern flank of the MCV,
but there is an echo free area across the west where some
subsidence may be occurring beneath and behind the MCV. Exactly
how this feature will progress is uncertain, but latest high res
guidance suggest the better thunderstorm coverage will be offset
to our eastern Panhandles as the MCV slowly drifts east through
this evening. Will need to watch how things go over the next 6
hours or so, with a possible cancellation of the watch by this
evening if dry trends continue for the west. Otherwise, will
continue to be a very moist environment with PWATs around 1.5-2.0
inches and MLCAPE values up to 2000 J/kg across the CWA. This
will lead to strong thunderstorms possible into the evening east
of the MCV with wind and heavy rain being the main concern. Some
localized flooding is possible given weak mid level flow and deep
moisture in place. Another area will need to watch for convection
at least through Friday will be along and behind the boundary
currently sitting along the I40 corridor. This boundary may shift
north some over the next 24 hours and may also take a more
northwest/southeast orientation as surface high pressure tries to
build into the Midwest states.

Showers and thunderstorms will continue in the forecast through
the extended as the upper level high begins to reform further to
our west with a more pronounced trough over the eastern half of
the CONUS. This will put the Panhandles in more dominant northwest
flow especially next week. In addition, deterministic guidance
indicates a baroclinic zone backing into the Panhandles from the
east with a positive theta-e axis setting up across the western
Panhandle. This should be a focus area for convection especially
late in the weekend into early next week. It should be noted that
models differ some on the extent of negative theta-E air advecting
in from the east, and thus will have an impact on which areas see
increased thunderstorm coverage. Any storms that develop next week
may also have increased concern for severe potential as mid level
flow increases some along with better veering profiles.
Temperatures should be near or slightly below normal through the
extended as cloud cover keeps temperatures moderated.

Ward

&&

.AMA Watches/Warnings/Advisories...
TX...Flash Flood Watch until 7 AM CDT this morning for the following
     zones: Dallam...Deaf Smith...Hartley...Oldham.

OK...Flash Flood Watch until 7 AM CDT this morning for the following
     zones: Cimarron.


&&

$$

29/11



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