Area Forecast Discussion
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FXUS64 KLUB 172057
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
357 PM CDT Sun Sep 17 2017

.DISCUSSION...
Similar to Saturday afternoon, another round of organized convection
was underway this time and could prove more robust given improved
instability and deep layer shear. Surface analysis at 3 PM featured
a stationary front curling NW-SE from near Hereford to Jayton, with
a surface trough aligned from Hereford SW to Carlsbad. Strong
heating along the surface trough should focus the greatest
coverage of storms in this area, with some flourishing likely as
this activity eventually crosses the front. Thanks to a 60+ knot
200 mb jet atop the region, 0-8 km shear of nearly 50 knots with
SBCAPEs around 1500 J/kg will support organized storm modes at
times including supercells. Favorable 0-1 km shear on the cool
side of the front could certainly foster low level mesocyclones
and perhaps a brief tornado. Otherwise, model consensus is for the
brunt of storms to affect the northern half of our CWA through
the evening, before dwindling overnight following the passage of a
subtle trough in cyclonic SW flow.

Monday opens with a transition to deeper westerly flow complete
with a warmer EML. Although most of the operational models are dry
on Monday, data from WPC and various high resolution CAMs support
a small window for storm development in the afternoon, mainly near
the surface trough progged to reside over our western zones. Even
with warming aloft, moisture convergence and favorable lapse
rates aloft do appear to support at least isolated storm development.
By Tuesday, even warmer air from 700-500 mb will advect through in
advance of a shallow upper trough. Stronger westerly flow should
serve to mix a dryline off the Caprock while also pushing highs
well above normal region wide. How well the dryline can convect by
late day is unclear, so we have retained the broad slight chance
PoPs in our Low Rolling Plains counties. Thereafter, the upper flow
will slowly back southwesterly in advance of a longwave trough
progged to occupy the western CONUS by late week. The only change
made to the forecast for late week was to skim back on PoPs across
the eastern half of our CWA in response to meridional flow
focusing farther west and translating much slower to the east into
Saturday. This fits well with energy digging and slowing across the
Desert SW which could open the door to repeated rain episodes
from eastern NM through the TX South Plains - and perhaps regional
flooding events which is not that uncommon this time of year.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

93



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