Area Forecast Discussion
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FXUS64 KLUB 241605 AAA

Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
1105 AM CDT SAT SEP 24 2016

Minor update to increase PoPs modestly and expand them westward
slightly through 18Z. Widely scattered elevated showers and the
occasional isolated thunderstorm continue to develop across
roughly the southeastern 2/3rds of the CWA within moist
southwesterly flow aloft and in advance of a surface trough/weak
front that has moved into the southwest Texas Panhandle and
western South Plains. The surface boundary will make only minimal
eastward progress today, perhaps to around the I-27/US-87
corridor, as the parent upper low lifts into the northern High
Plains. Still expect more widespread and robust convection to
develop along and ahead of the surface trough this afternoon as
instability increases and inhibition wanes. Deep layer wind shear
is not that impressive (around 20-25 knots), but the instability
could still support a few brief stronger updrafts. That said, the
greater threat with this activity will be locally heavy rainfall
as the convection ingests rich moisture, with PWAT values well in
excess of 1.5 inches off the Caprock. The bulk of the activity may
shift south and east of the area this evening for a time before a
developing upper low well to our west (over southern AZ/NM and
northern Mexico) and 700 mb low near the Big Bend pull the
moisture and shower/storm chances back westward across the area. A
heavy rain threat will redevelop, favoring the Rolling Plains
where moisture and instability will be maximized, though most/all
of the CWA will likely see some rain. A strong cold front is still
on track for Sunday (though with some timing uncertainty), with
gusty northeasterly winds developing. Cloud cover and areas of
rain will continue post-frontal, though rain intensity should
gradually wane.


.PREV DISCUSSION... /issued 651 AM CDT SAT SEP 24 2016/

VFR is expected to prevail though short term guidance indicates a
chance for brief MVFR ceilings near KCDS shortly after sunrise.
Showers with isolated thunderstorms are expected to develop later
this afternoon but left out of TAF given uncertainty in timing and
proximity to terminals but did add VCSH for all three locations.

PREV DISCUSSION... /issued 335 AM CDT SAT SEP 24 2016/

Trough associated with strong upper level low centered over central
Rockies will push through the Four Corners region into the Colorado
Foothills today. As flow begins to split and weaken around the base
of the trough, ample moisture will slowly spread westward from the
Rolling Plains across the South Plains with PWATS ranging from 1.0
to 1.75 area wide.

Best PVA will be across Rolling Plains later this afternoon under
weakening flow aloft and anemic surface pressure falls. Struggling
to have faith in short term guidance continuing to suggest POPS
over the South Plains before noon today. HRRR/GFS/ECMWF confine
deepest convection to our north across the Texas Panhandle for the
first half of today, where it belongs. By mid-afternoon we should
see a developing CU field begin to produce showers and tstorms
across the Rolling Plains and struggle to become more widespread to
the west as convergent upper level flow begins to move in from the
west. Shower and thunderstorm activity should push east and south of
area by nightfall. Severe potential is low but some storms in our
Rolling Plains counties could be come strong enough to produce
some heavily local rainfall and gusty winds.

Saturday night should provide a break from rainfall for most of us
as upper level energy that splits from polar jet today will
reorganize back into a closed low to our west and begin to
retrograde with enhanced east-southeast upslope flow at the
surface. Setting Sunday up for more widespread rainfall across our

It appears that guidance is maintaining a fairly consistent picture
from last night with respect to the evolution of the low across the
Great Basin.  Indications are that the parent system will eject into
the Northern Plains with another low forming back across SRN NM/AZ
thence move SWRD to the Gulf of California (a bit of a compromise
betwixt solutions last night.)  While initially impeded by high
pressure over the Great Basin early next week, the low should slide
into SRN California by mid-week before becoming absorbed in the mean
flow to our north as ridging builds into Texas.

Guidance has trended faster with respect to the precipitation
tapering on Sunday.  Data hints that we should see chances roll off
from north to south during the day though the southeastern zones
should see activity well into the evening and overnight hours. QPF
looks to result in some decent accumulations though, at this point,
given the dependence of mesoscale processes, do not have much in
the way of focused flood concerns. The highest totals should be to
our south and southeast. By Monday, it would seem as if the rain
should be largely over though have elected to trend things
downward instead of pulling them outright given the uncertainties
of the synoptic evolution during this period. Cut off lows across
NRN MX are hard for the models to handle with accuracy. Once rain
does clear out, it dry weather is anticipated for the remainder of
the extended with high temps in line with early fall expectations.


.LUB Watches/Warnings/Advisories...


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