Area Forecast Discussion
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FXUS64 KLUB 200750

Area Forecast Discussion
National Weather Service Lubbock TX
250 AM CDT Thu Jul 20 2017

The mid-level disturbance that provided the weak lift and notable
moistening aloft that aided in the unexpected convection that
flirted with the far southwestern South Plains yesterday afternoon
has now shifted into New Mexico and Far West Texas. Behind this
disturbance early morning water vapor imagery shows a return of very
dry easterly flow advecting into the region. This will likely
suppress storm development this afternoon, though progged soundings
show little CIN/cap and weak instability at peak heating, so we
can`t completely rule out a brief, small rogue shower. The same will
be true tomorrow afternoon/evening, and the latest NWP even suggest
a subtle mid-level vorticity maximum currently residing along the
Gulf Coast will move into the area. This setup could be slightly
more conducive to isolated late day convection than today, though
very dry air above the boundary layer and residual subsidence from
the temporarily fleeting upper ridge will have something to say
about that. Given this and the fact that all guidance examined aside
from the ECMWF keep the CWA dry we could not justify PoPs greater
than 10 percent. Outside of the minimal PoPs, the weakening upper
ridge that will be gradually shifting further to our east through
the end of the week will still exert enough influence to keep the
fairly typical summer heat going. In fact afternoon temperatures may
edge up a couple of degrees from today into Friday and Saturday.

Beyond that we are still watching the potential for increasing rain
chances late this weekend into early next week. This will occur as
the departing/weakening upper ridge along with a potent shortwave
trough digging over the Great Lakes allow the better fetch of
monsoon moisture to bend eastward toward and across the region. The
latest guidance has trended more favorable for thunderstorm
development across at least the northern and western zones (and
perhaps a good chunk of the FA) late Sunday and Monday. The 00Z
GFS and NAM even suggest an outflow aided front may briefly dip
into the South Plains on Sunday providing an additional focus for
storm development. The lingering deep moisture and residual
boundaries may keep storm chances going Monday before an upper
ridge is forecast to redevelop across the central and southern
Rockies and adjacent High Plains. The building ridge would likely
quelling thunder chances and heat things back up moving into the
middle of next week after a brief/modest respite from the West
Texas summer heat. Before then, elevated PWATs (1.2-1.5+ inches)
and weak steering flow may bring the risk for locally heavy rain
late weekend into early next week, at least for parts of the




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