Area Forecast Discussion
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202
FXUS64 KLUB 010445
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
1145 PM CDT TUE MAY 31 2016

.AVIATION...
A convective system moving across the area tonight in conjunction
with a cold front moving south, so have default thunder mentioned
at both KLBB and KPVW until 08z. KCDS looks like further from
center so primarily rain shower. Short term solutions suggest
system should clear southeast afterwards and will get a break
before shower chances return post frontal on Wednesday. MVFR
ceilings look likely by early Wednesday morning. RMcQueen

&&

.PREV DISCUSSION... /issued 655 PM CDT TUE MAY 31 2016/

AVIATION...
Very chaotic mesoscale boundaries crossing the region this evening
and irregular storm motion leads to high levels of uncertainty
regarding short term thunderstorm chances. Potential impacts to
the aviation community are high.

Short term solutions at the moment unfortunately do not seem to
be offering much confidence. One important feature is the old west
to east outflow boundary lying between KLBB and KMAF. This is
where we have seen a number of showers and relatively weak
thunderstorms thus far, and so far not showing much development to
the north. A well defined instability axis is running just north
of this boundary from west northwest to east southeast with the
strongest gradient just south of KLBB. Early this evening anyway,
this is where we should expect best thunderstorm coverage and
likely some intensification.

Another region with more immediate impact is just east of KCDS
with thunderstorms slowly back-building to the west towards
Childress. A little hard to rationalize this deviant motion but
low level moisture is increasing from the east this evening.

And in the background, the upper level southwest flow is gradually
backing with the slow approach of low pressure through northwest
Mexico and a likely disturbance being ejected our way across
southwest Texas now.

Short term RADAR trends support backing off on start of thunder
both KLBB and KPVW and only slightly backing off for KCDS. Expect
activity to fill in during the early to mid evening as the
disturbance approaches from the west.

Later in the evening into the overnight, a cold front/outflow over
the Panhandle should get a better nudge to the south as an MCS
(Mesoscale Convective System) developing over northeast New
Mexico rides southeast towards the western Panhandle. Arrival of
this front may coincide with start of best shower chances. There
is a chance this could lead to a larger MCS rolling southeast into
the area with potential very high impact on flying conditions.

And later in the night, a low cloud layer seems most certain
still for KCDS but also possible at KLBB and KPVW but interaction
with thunderstorms early tonight hampers confidence in timing.

So, lots of potential impacts for the aviation community. We will
update TAFs based on current trends and hope to have more clarity
on later ceilings and thunderstorm impacts with the 06z TAF
package. RMcQueen

PREV DISCUSSION... /issued 329 PM CDT TUE MAY 31 2016/

SHORT TERM...
Satellite/Radar this aftn shows convective cells growing in number
and strength along a remnant outflow boundary stretching from
eastern NM near Tatum across the southwest corner of the CWA into
the northern Permian Basin. Activity earlier across the Rolling
Plains that was sparked by initial broad scale lift has since
dissipated but new cumulus growth has returned there. Surface obj.
analysis shows theta-e ridge along the outflow boundary extending
north into the eastern Plains of NM with ML CAPE values on the
order of 1000-1500 J/kg.

Convective models thus far have been in good agreement on activity
developing along the outflow this afternoon and working east with
second batch of storms organizing and moving off the higher terrain
later this evening. Overall steering flow is weak and thus storm
motions will be slow again this afternoon and evening justifying the
concern for localized heavy rainfall. Main concern will be with high
rainfall rates on the 1-2 hour period but pinpointing those at this
time with any certainty remain outside of predictability. Otherwise,
severe potential will be limited with weak deep layer shear
supporting mainly outflow-dominant storms but some temporary
supercell structures and updrafts supporting large hail can`t be
ruled out either.

Broad-scale lift will continue across west Texas overnight as the
upper low and attendant positively tilted trough axis across NM
approaches. Additional showers and storms will likely develop in
this pattern along a synoptic scale front/enhanced outflow boundary
moving south out of the Panhandle. This activity will linger through
the morning Wednesday with another slow moving complex developing
across the area during the afternoon. Temperatures will be cooler on
Wed with combination of clouds and precip through much of the day
limiting instability and the overall severe potential, however, very
slow forward motions of the storm complex will continue a heavy rain
potential. With a preference for more short-fused Flash Flood
watches and the concern that the boundary position and eventual
storm complex may be far removed from where the latest models have
it, decided to hold off on any highlights at this time.

LONG TERM...
An extended period of rain to the West Texas region will come to an
end later this week.

The slow moving upper level low currently located over southern
Arizona will gradually move to the south of us on Thursday slowly
ending precipitation for much of the region. Surface ridging will
bring in lower theta-e air at the lower levels of the atmosphere on
Thursday. However, mid and upper level moisture will remain over the
region and stick around longer. This upper low will continue its
slow or nearly stationary movement over central/south Texas late
this week. This will leave the Rolling Plains under some weak
influence of this system on Friday and Saturday. The rest of the
region will likely be dry under greater influence of a building
upper level ridge from the west.

This uncharacteristic pattern for early June will continue through
early next week. Models continue to depict northwest flow storms
early next week within the upper ridge and mid level moisture.
Although subsidence in between the upper ridge and low to the
southeast will attempt to suppress any convection at least some
minor mention is warranted in the forecast at the moment.

&&

.LUB Watches/Warnings/Advisories...
None.
&&

$$

99/99/05



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