Area Forecast Discussion
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FXUS64 KLUB 152022

Area Forecast Discussion
National Weather Service Lubbock TX
322 PM CDT Fri Sep 15 2017

Favorably diffluent upper flow remained over the region this
afternoon in the wake of yesterday`s upper ridge, but earlier
scattered showers and storms had since exited into western
Oklahoma. Modest subsidence behind this ascent was serving to
keep much of the area void of boundary layer instability, but
visible satellite clearly showed some agitated Cu focusing over
the plains of NM near a surface trough. Sufficient CAPE and weak
CIN in this vicinity should allow for some storm development in
the coming hours, with easterly propagation not an issue given
700 mb flow around 25 knots. Expectation is for isolated storms
to affect mainly our western zones through the evening, but with
moist SW flow persisting aloft this activity could easily persist
farther east after sunset.

For Saturday, the moisture axis aloft will remain largely unchanged
from SW-NE over the South Plains. Models agree that a belt of
stronger upper tropospheric winds (about 60 knots at 300 mb)
will overspread the region throughout the day ahead of broad upper
troughing extending through the Desert SW. This along with some
eastward displacement to the aforementioned surface trough should
focus isolated to scattered storm development in the afternoon.
Raised PoPs a bit to account for this otherwise favorable regime,
but rain amounts should be light given adequate storm motions.
Opted to keep high temps cooler than today given less downslope
flow component, but MOS has trended suspiciously warm which the
midnight forecast crew will revisit. Distant passage of a large
trough through the central and northern Great Plains will release
a cold front into at least the northern Panhandle by Sat night
which could ooze south on Sunday and keep our northern zones even
cooler than presently advertised.

For Sunday, upper winds are progged to veer a touch more westerly
and gradually dry out under a semi-zonal flow, before a more
significant longwave trough evolves across the western half of the
CONUS early next week. Drier and more zonal flow ahead of this
trough should serve to skim back on the rain chances as we head
into midweek, particularly on the Caprock as the surface trough
migrates east. This regime will keep temps above normal with the
potential for even warmer highs than the Superblend indicates.
Regarding the longwave trough unfolding west of the Continental
Divide by early next week, the GFS ensembles are reasonably
well clustered in lifting a lead wave out of this broader trough
by Wed. Should this happen, then a cold front is likely to
approach the southern High Plains and possibly augment our low-end
PoPs. Not until late week do PoPs show more life as the upper
flow slowly trends more meridional ahead of the large scale trough.




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