Area Forecast Discussion
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FXUS64 KLUB 220309 AAA

Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
1009 PM CDT Sat Oct 21 2017

The cold front has now cleared all but the far southeast corner of
the CWA, right on schedule. Scattered post-frontal showers and
thunderstorms continue to persist across the southern Rolling
Plains as of 03Z, but these should come to an end over the next
hour as the better forcing, moisture and instability shift to the
south and east of the FA. We have trimmed the mentionable PoPs to
the southern Rolling Plains through 04Z and then dried the entire
CWA out thereafter. The northerly winds were already diminishing
behind the front. The combination of the light winds, clearing
skies and surface ridging settling over the South Plains will lead
to a cool overnight. Lows by early Sunday morning will likely dip
into the middle and upper 30s over the northwestern and western
zones, with lower to middle 40s common elsewhere. The ongoing
forecast has this well accounted for and no adjustments were made
beside the tweaking of the PoP and weather grids.


.PREV DISCUSSION... /issued 640 PM CDT Sat Oct 21 2017/

Scattered convection was now shifting east of KLBB and KPVW, but
could affect KCDS for the next hour or two. Otherwise, a cold
front has already pushed through KPVW and KCDS and will move
through KLBB around 0020Z. Breezy northerly winds will blow for a
few hours after the FROPA before they weaken and remain light
through the remainder of the TAF cycle. VFR conditions will be the
rule, aside from a brief visibility restriction possible at KCDS
should any storm move directly over the terminal this evening.

PREV DISCUSSION... /issued 316 PM CDT Sat Oct 21 2017/

Cold front was entering the southern TX Panhandle shortly after
2 PM and remains on track to clear much of the South Plains by
sunset. Thermal ridging ahead of this boundary is host to a
corridor of steep low level lapse rates, which despite meager
boundary layer moisture, is already garnering stable cumulus.
However, colder mid level temps are inferred exiting eastern New
Mexico within the base of an upper trough. As this trough axis and
increasing ascent continue eastward, some high based showers,
storms and virga are likely to evolve on the Caprock with a window
for organized and deeper convection near Highway 83 coincident
with deeper moisture and SBCAPEs of 2000 J/kg. Microbursts remain
the primary concern in this setup with any severe hail favoring
the Rolling Plains.

Following modest pressure rises immediately behind the front with
a few hours of 20 mph northerly winds, speeds will scale back
around midnight as the pressure ridge envelops the region. Chose
to undercut models for low temps overnight, especially in our NW
zones where the lowest dewpoints around 30 degrees should linger
the longest. A light freeze is possible, but is not as definitive
as locations farther north in the western Panhandle. Else, this
cool ridging will linger on Sunday and make for a perfect day to
be outdoors enjoying some hot apple cider under full sun with
light winds. Quick exodus of this surface ridge by Sunday night
will precede deeper and drier NW flow complete with a backdoor
cold front by Monday afternoon. Challenge in the extended realm
remains the arrival of a strong cold front sometime Thursday or
early Friday pending the evolution of a sharp trough. At present,
models and ensembles are in fair agreement with this trough,
although the ECMWF has shown the most run-to-run variability
despite preferring a more westerly longitude than the GFS. Pattern
recognition supports a sharp cooldown by late week with perhaps a
widespread freeze as the coldest dome of cP air arrives Friday
into Saturday.




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