Area Forecast Discussion
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FXUS64 KLUB 220439

Area Forecast Discussion
National Weather Service Lubbock TX
1139 PM CDT SUN AUG 21 2016

Low level moist southeast flow overnight still expected to bring
areas of MVFR clouds on the Caprock. The RAP and HRRR short range
solutions have been trending a little more moist and earlier with
cloud arrival. So minor adjustment for earlier onset of low clouds
at both KLBB and KPVW late tonight. Solutions were also trending
towards an area of surface saturation southwest of KLBB where a
lingering patch of lower clouds currently resides and will need
monitoring through the night for possible airport impact.
Otherwise, shower chances will remain small until late Monday, but
solutions still hold best chances away from TAF sites at this
time. Healthy cumulus field is likely. RMcQueen


.PREV DISCUSSION... /issued 701 PM CDT SUN AUG 21 2016/

A weak upper level impulse will eject slowly through northeast New
Mexico early tonight, but with shower and thunder remaining mostly
within New Mexico and not expected to approach any TAF site. This
wave ushering in enhanced southerly low level flow overnight with
increasing moisture and areas of MVFR ceilings anticipated. Short
range forecasts are not overly bullish on these clouds with the
most recent hourly runs, but we are not changing just yet. Will
take a look closer after the 00Z data and solution runs are
available. Whatever lower clouds and/or moisture move in, we
definitely expect another healthy cumulus cloud field by late
morning or midday Monday and through the afternoon. The best
shower or thunder chances through 00z Tuesday anyway are projected
just south/east of KLBB and KCDS and west/northwest of KPVW.

PREV DISCUSSION... /issued 306 PM CDT SUN AUG 21 2016/

We are in the midst of another beautiful late August day with 19Z
temperatures only in the 70s and lower 80s. This heating coupled with
enough residual low-level moisture has promoted the development of a
decent cumulus field across the area, though no precipitation
locally as of this writing. The closest convection was scattered
across parts of central and eastern New Mexico where deeper moisture
was interacting with one of several upper level disturbances across
the southwestern states. This activity may try to propagate toward
our far western zones through the late afternoon and evening hours
as the disturbance aloft ejects northeastward. However, as we have
seen to this point, it will struggle to do so as it finds a less
favorable thermodynamic environment with eastward extent thanks to
a surface ridge axis that is nosing into West Texas. Even so, with
mixed signals in the NWP and the convection not that far away ATTM,
have decided to carry a minimal thunder mention out near the TX/NM
line. The reservior of richer moisture over the central/southern
parts of the state will then be drawn back northward as the surface
ridge shifts further east, pressures fall in the lee of the Rockies
and the stationary front currently near the coast washes out and
lifts back northward. The best thrust of the moisture return is
progged into the Rolling Plains, though we could even see a bout of
low clouds up on parts of the Caprock Monday morning. With the
return of the deeper moisture will come improving rain chances.
It is not clear whether there will be much/any in the way of
upper support, but increased moisture/instability along with minimal
inhibition by afternoon should be enough to generate isolated to
scattered convection, with the best chances/coverage favoring the
Rolling Plains. Although storm coverage remains somewhat ambiguous,
PWAT values of 1.75-2.25 inches will provide a locally heavy rain
threat with any storms that do form. Further west, up on the
Caprock, more isolated convection may form, though this is less
certain, and only a low thunder mention was maintained.

It will be another relatively cool night tonight, though readings
should moderate a bit from yesterday, particularly across the
southern zones as moisture begins to improve. Another day of below
average temperatures will follow on Monday with highs generally in
the lower to middle 80s.

Through midweek will see some fairly rich and deep moisture drawn
northward around the western end of an upper ridge centered over
the Gulf Coast states while a trough that will develop across the
western CONUS will provide a series of upper level short wave
troughs to work on that moisture. Result is expected to be periods
of isolated to scattered thunderstorms. The quality of this
moisture is indicated by progged PWATs between 1.75" and 2.25"
Monday evening slowly decreasing through the week. Precipitation
chances still may be enhanced towards Wednesday night and
Thursday, but that still depends upon movement of a cold front
which the models continue to struggle with. For example, the GFS
now stalls the front across the Panhandle while the ECMWF pushes
the front into the South Plains forecast area. The upper trough to
the west supports the idea of keeping this front further north
than the most recent that moved well south of the forecast area.
Low confidence at this time with the frontal movement, but even
if further north per the GFS, there will potential for organized
outflow to push south into the forecast area to serve as the focus
for convection. Thus, will keep the period from Wednesday night to
Thursday night with the highest PoPs of the forecast period.


.LUB Watches/Warnings/Advisories...


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