Area Forecast Discussion
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FXUS64 KLUB 260842

Area Forecast Discussion
National Weather Service Lubbock TX
342 AM CDT Tue Sep 26 2017

...Flood Watch remains in effect for the southeast South Plains
and all of the Rolling Plains from 7 am today through 7 am

A very moist atmosphere remains in place across the center of the
nation (including West Texas) with this morning`s Total Precipitable
Water satellite imagery showing values of 170 to 200+ percent of
normal stretching from northeast Mexico through the upper Midwest.
This atmosphere was supporting two clusters of convection over
the region as of 08Z, one advancing into the southeast Texas
Panhandle and northern Rolling Plains and a second approaching the
TX/NM line through east-central NM. The lead MCS moving across
the WTM domain has generally produced rain totals in the 0.50 to
1.50 inch range, including a few pockets of brief torrential rain
(including 0.95" at Reese Center in 15 minutes). These
amounts/rates are likely causing pockets of minor flooding, though
they are progressive enough to stave off more significant
flooding at this point. There is general agreement in the short
term NWP that the two overnight complexes will gradually wane
toward and after daybreak as their outflows and the effective
frontal zone outpace the convection. However, there is also a
decent signal that more intense convection will redevelop along
the advancing front/outflow across the Rolling Plains this morning
bringing the risk of a quick 1 to 3 inches there. This fits well
within the previous forecast scope and justifies maintaining the
Flood Watch for the southeast zones which starts at 12Z and
continues through 12Z Wednesday.

At least parts of the CWA will see a lull in precipitation this
afternoon, but more widespread rain (perhaps with a few rumbles of
thunder) will likely redevelop tonight. This will occur as the
next iteration of a closed low takes shape within the western
trough across the Desert Southwest. The forming upper low will act
to both increase upper level divergence downstream over New
Mexico and West Texas while also drawing the plume of eastern
Pacific moisture (partially from the remnants of Pilar) up and
over the frontal zone. The heaviest rain will likely favor the
southeast zones tonight, though light to moderate rain will be
possible across most of the area, with the northwest zones being
the one spot that could miss out. The synoptic scale weather
pattern will be slow to evolve meaning rain chances will persist
into Thursday and perhaps even Friday, though a decrease in the
mid-upper level Pacific moisture fetch along with drier surface
ridging building in from the northeast will likely temper rain
coverage and intensity.

The medium range NWP is now in better agreement that the
southwesterly flow aloft through the week will quickly transition to
near zonal flow above the South Plains by Saturday. This will carry
in drier air and likely bring an end to the rain chances by this
weekend. However, there are indications another trough will traverse
the western states this weekend before emerging over the central and
northern High Plains Sunday or Monday. It is unclear if the southern
plains will acquire another moisture tap or if upper level ridging
beneath the trough will hold and keep the region dry. Given the
uncertainty we have kept the latter part of the forecast dry for

Cloudy (and at times wet) post-frontal conditions will keep
temperatures cool this week, with highs generally in the 60s to low
70s. A few spots may not make it out of the 50s if/where the wet
conditions are most prevalent. A warming trend should finally kick
in this weekend into early next week as drier conditions and the sun
return. Even so, did favor the slightly tempered blended guidance
given the wet ground that will be in place.


Flood Watch from 7 AM CDT this morning through Wednesday morning
for TXZ031-032-036>038-041>044.



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