Area Forecast Discussion
Issued by NWS Amarillo, TX

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254
FXUS64 KAMA 010409
AFDAMA

Area Forecast Discussion
National Weather Service Amarillo TX
1109 PM CDT THU JUN 30 2016

.Aviation...
For the 06Z TAFS, expect ongoing showers to move east of the
terminals by the start of this TAF cycle. Have carried vicinity
mention as there could be a few lingering showers during the onset of
this cycle. Cleared all terminals of convection mention by 09Z and
should remain that way into the daylight hours. Another round of
convection is expected tomorrow primarily impacting the northern
terminals. Have inserted PROB30 groups into both KDHT and KGUY for
tomorrow afternoon when the better chance for storms exist.

&&

.Prev Discussion... /Issued 705 PM CDT THU JUN 30 2016/

Aviation...
For the 00Z TAFS...The short term concern for aviation will be winds
and locally heavy rainfall with thunderstorms moving slowly across
the Panhandles this evening. Winds may be variable with gusts up to
around 45 kts near the strongest storms. This round of storms should
be mostly east of the TAF sites by around 02Z to 03Z tonight, with at
least some chance for additional thunderstorms overnight. Given the
slow moving nature of these storms and scattered coverage, did not
include mention of thunderstorms in TAFs beyond 03Z at any site.
Amendments may be necessary if outflow from thunderstorms causes
significant wind shifts.

NF

Prev Discussion... /Issued 430 PM CDT THU JUN 30 2016/

Discussion...The main points of interest for this forecast package
are the continuing chances for showers and thunderstorms, as rain
chances will exist intermittently now through Tuesday afternoon.
Temperatures will also begin to climb back up through the weekend and
early next week we can expect to start seeing high temperatures
nearing the century mark.

Short Term...This afternoon through Saturday night...Showers and
thunderstorms are currently forming and moving through portions of
the Texas and Oklahoma Panhandles. Storms have initiated in Armstrong
County and other portions of the south central Texas Panhandle. These
storms have pushed out an outflow boundary which is making its way
northwestward towards the cities of Amarillo and Canyon. This will
shift winds to a more southeasterly direction behind it, and enhance
the potential for scattered storms to form. Additionally, there are
some small showers and thunderstorms beginning to move in from New
Mexico and Colorado ahead of a lee surface trough to our west. These
storms are expected to continue for the remainder of the afternoon
and evening hours, however more organized convection is likely during
the overnight and early morning time period. Any of the stronger
storms that form during this time will be capable of producing
strong, gusty winds and small hail.

The best locations for the aforementioned organized convection
continues to be the northern portions of the Oklahoma and Texas
Panhandles where frontogenesis associated with a surface trough is
strongest. This, coupled with ample moisture, northwesterly flow, and
isentropic ascent could allow for mesoscale convective system
formation overnight and into Friday morning. Precipitable water
values are around an inch to an inch and a quarter, which is
slightly higher than average. Therefore, any storms that develop and
hold together will have the possibility of producing heavy rainfall
that could lead to localized flooding.

Fairly weak northwesterly flow aloft will continue due to an area of
high pressure centered over New Mexico and the southwestern portions
of the Texas Panhandle. The ridge is expected to make its way
eastward and set up over the central portions of the Oklahoma and
Texas Panhandles. Once this feature transitions to our east, our flow
aloft will become more westerly. This is anticipated to occur by
Friday evening, and by Saturday Morning we should have returned to
northwest flow with yet another ridge building in from the west.
Meanwhile, at the surface a strengthening lee trough in the New
Mexico and Colorado area will increase chances for rain through the
weekend and eventually move through the combined Panhandles towards
the end of the day on Saturday.

Lorenzen

Long Term...Sunday through Wednesday night...Model guidance is in
good agreement that an upper level shortwave trough is progged to
move eastward across Kansas during the afternoon and evening hours.
A surface front will rapidly push through the area with northerly
winds of around 10 to 15 kts with slightly cooler air in it`s wake.
Precipitation chances around midday Sunday will be focused on the
southern and eastern portions of the combined Panhandles, with MLCAPE
around 1000 to 1500 J/kg in the moist airmass ahead of the frontal
boundary. Limited organization of convection may be possible ahead of
or along the frontal boundary, though bulk shear is limited. Dew
points ahead of the passing front will be in 60s, with PWV values
between 1.25 to 1.50 inches. This will present a threat for heavy
rainfall, with localized flooding should storms linger, in affected
areas on Sunday. Once the front clears the area, precipitation
chances will rapidly diminish afterwards. Late Sunday, a ridge of
high pressure will reorient itself but there is disagreement as to
whether the combined Panhandles will be under westerly or
northwesterly flow. Late Sunday into early Monday, guidance agrees
that return flow is progged with southerly winds returning to the
CWA. Highs on Sunday will be in the upper 80s to lower 90s, with lows
Sunday night in the lower 60s northwest to lower 70s southeast.

On Independence Day, model guidance remains somewhat split on the
next possible shortwave trough to approach the combined Panhandles.
The ECMWF continues to show signs of a suppressed ridge with a more
southerly approach for this next system, while the GFS is the most
robust with ridge redevelopment and northwesterly flow.  The
difference is enough that there is uncertainty as to the extent and
possible magnitude of thunderstorm activity through Monday afternoon
and evening.  The most aggressive solution, the GFS, is suggesting
MLCAPE of around 1500-2500 J/kg with 0-6 km bulk shear approaching
35 to 45 kts.  Meanwhile, the ECMWF is much less agressive with
MLCAPE around 500-1000 J/kg with negligible wind shear.  Both are
suggestive of PWV values around 1.30 to 1.60 inches, which would
present the possibility of rain efficient thunderstorms.  For now,
have held with a slight chance of thunderstorms area wide until more
certainty can be determined Independence Day.  High temperatures on
the 4th of July are expected to be in the lower to mid 90s areawide,
with low temperatures Monday night into Tuesday morning around the
lower 60s northwest to lower 70s southeast.

Tuesday through Thursday, the long range model guidance is showing
some agreement as to how the ridge of high pressure will reassert
itself over the region.  Both models show the ridge either centered
over the area or just to our northeast, which would place the region
under height increases and increasing warm air advection.  Given
positioning of the ridge, it will prove more difficult for
convection to occur in our area with H5 temperatures around -4 to -6
degrees Celsius.  Have opted to lower PoP chances next week, and
continue forecasted high temperatures for the area in the upper 90s
to around 101 degrees areawide.  Low temperatures should be in the
mid 60s to mid 70s each night late in the period.

Bieda

&&

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

&&

$$

14/6



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