Area Forecast Discussion
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FXUS64 KLUB 141128

Area Forecast Discussion
National Weather Service Lubbock TX
528 AM CST Sat Jan 14 2017

Generally poor flying weather will continue for at least the next
24 hours. LIFR with periods of VLIFR will be likely this morning
as low level moisture further increases areawide. Additionally,
light freezing rain will be possible at KPVW and KCDS this morning
as temperatures hover at or just below freezing. Isolated
thunderstorms will also be possible late this morning into the
afternoon at all TAF sites.


.PREV DISCUSSION... /issued 444 AM CST Sat Jan 14 2017/

Deep moist isentropic ascent will continue to persist through the
day today. This lift will be complemented by a short wave lifting
through West Texas this morning. Spotty showers this morning are
therefore anticipated to expand by late in the morning through the
afternoon hours. Furthermore, a shallow layer of frontogenetical
forcing will exist over the western South Plains through tonight.
This may enhance precipitation totals on the caprock when combined
with the isentropic lift and lift from the short wave. A mid level
dry layer which prevailed all day yesterday was nearly eroded early
this morning leaving a saturated atmosphere. Embedded thunderstorms
will be likely as well this morning and afternoon as buoyancy
increases. The buoyancy will be weak but spread over a large portion
of the sounding resulting in some thunder mixed in with the rain
showers. Temperatures are still troublesome during the morning hours
with an extention of the subfreezing surface air into the southern
Rolling Plains. Wet bulb potential has eroded with dew point
depressions less than three degrees or so across the entire region.
Warmer near surface temperatures will spread northward today
attempting to erode the cool surface air. The onset of heavier
precipitation will also likely raise temperatures with the very warm
layer just off the surface.

A lull in precipitation will follow this evening in the wake of the
departing short wave. The main lift from the upper level low will be
far off to the west resulting in weaker isentropic lift during the
overnight hours. We will undergo more significant height falls
during the early morning hours on Sunday as the upper low approaches
El Paso. However, much of the lift will arrive after daybreak Sunday.

The potent upper low just west of El Paso early Sunday will
progress east and northeast during the day, rolling directly
across the western South Plains Sunday evening. Earlier trends of
slowing this system still seem on track. Strong upwards forcing
will spread over the area while mid and lower levels remain
nearly saturated. High rain chances will be valid throughout the
day, but may be most concentrated teamed with the strongest deep
upward forcing late in the day. It appears that surface based
instability will be minimal in our area, better just to the south
perhaps, but enough mixed layer instability exists for continued
thunder mention throughout the day. And with the strong lift late
in the day might yet support a few stronger elevated reflectivity
cores favoring our southern zones, and southeast in particular.

The slightly slower passage will allow fairly high mention of rain
into the evening for eastern zones, though a little uncertain if
the convective activity will lower chances as quickly northeast
as indicated by the WRF/NAM. So, opted to improve mention a bit
Sunday evening back to the central and western zones. The path
across the area also still suggests at least pattern recognition
of some snowfall potential across the northwest; deterministic
solutions are only marginally cold enough, however. But we are
holding on to a low mention and minor accumulations for our
northwest snow belt zones, just because how many times we`ve seen
it snow on back sides of such systems.

Upper low will clear northeast early Monday morning with
improving conditions. Moisture will remain dwindled into Tuesday
as a trailing trough of some sort gradually passes overhead.
Solutions remain quite distorted and in discontent over how this
trough will morph and what kind of impact it may have; opted to
add however a very low shower mention west and northwest Monday
night. And its possible the main upper trough will not pass until
Wednesday. Cannot completely rule out instability showers, though
drying in lower levels will limit effectiveness. Temperatures
should be held back through Tuesday before warming.

Later in the week, a high speed Pacific jet will move onto the
California coastline, sending perhaps a series of fast moving
waves our way, and eventually a deeper upper low by the middle of
next weekend. Pattern recognition leans towards dry, windy and
somewhat mild, with limited moisture overall; will attempt to
quantify potential impacts better next time. RMcQueen


Freezing Rain Advisory until noon CST today for TXZ023>026-



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