Area Forecast Discussion
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FXUS64 KLUB 210928

Area Forecast Discussion
National Weather Service Lubbock TX
428 AM CDT Wed Jun 21 2017

Nocturnal storms have largely refocused within a theta-E axis
oriented just east of I-27, with further assistance from a 30 knot
LLJ per regional 88D VWPs. Expectation is for isolated to
scattered storms to continue redeveloping southward, mainly off
the Caprock, before diminishing toward 7 AM as the LLJ wanes.
Otherwise, weak upper ridging extending over the area from an
upper high in AZ is still progged to lose 10-20 meters of strength
at 500 mb today. This scenario should improve chances that a more
comprehensive cluster of storms affects our CWA tonight,
primarily across our NW zones where the theta-E ridge is progged
to focus. Initiation is still favored from northeast NM into the
northwest Panhandle along a nearly stationary surface trough, with
15-20 knots of NNW steering flow to transport convection south.
Forecast profiles show tall, deeply-mixed boundary layers with
more DCAPE than CAPE in many areas, so some downbursts will be
favored tonight. Otherwise, morning high cloud debris should
easily thin before noon, so high temps were boosted a few degrees
over MOS given its recent cool bias.

Thursday is likely to play out very similar to today, both with the
threat of pre-sunrise storms and additional height falls aloft
within the ridge axis. The biggest difference involves a thermal
ridge from 850-700 mb drawing closer which should boost max temps
a few degrees over today, but not enough to warrant a heat
advisory. Afternoon storm initiation will again be preferred along
the surface trough in the high plains of NM through southeast CO.
Models indicate nearly 40 knots of northerly steering flow by Thu
evening which may require higher PoPs than slight chance in our
NW counties.

Global models are now in sync with a cold front arriving on Friday
courtesy of broad troughing engulfing most areas east of the Rockies.
This front is likely to slow somewhere in our vicinity during the
day on Fri as winds curl easterly and transport rich moisture
westward. Moist upslope flow, a slow-moving boundary, ample CAPE,
and 35-45 knots of 0-6 km shear certainly fit the bill for an organized
severe threat on Friday. Where models differ is how many ripples
within the broad trough affect the frontal boundary through the
weekend. The ECMWF and CMC retreat the front on Sat before surging
it back south Sat night or Sun, resulting in a significant spread
of potential high temps from the 70s to 100s. Opted to stick with
the more stable Superblend depicting easterly low level flow
until a more definitive signal emerges in models. Otherwise, such
a cyclonic NW flow regime could easily support heavy rain episodes
at times this weekend given rich PWATs of 1.5" to 2". Rain chances
look to come to an abrupt end o/a Tue as the upper high amplifies
and mobilizes east across NM and eventually West TX.




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