Area Forecast Discussion
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FXUS64 KLUB 070524

Area Forecast Discussion
National Weather Service Lubbock TX
1124 PM CST Tue Dec 6 2016

IFR conditions still look likely at KLBB and KPVW between sunrise
and noon. West winds should then scour moisture followed by a
strong cold front that will bring north winds and MVFR cigs.


.PREV DISCUSSION... /issued 849 PM CST Tue Dec 6 2016/

The forecast was updated to account for lower overnight
temperatures. Some TTU mesonet sites have already reached their
forecast low this evening or were approaching it. Scattered clearing
of the high level cirrus and relatively light winds have allowed
temperatures to rapidly decrease this evening at some locations
more than others. Low level moisture will continue to increase
through the rest of the evening and overnight hours. Additionally,
low stratus is expected to move in early Wednesday morning.
However, these activities will likely be too late to greatly
affect the already low temperatures observed.

PREV DISCUSSION... /issued 549 PM CST Tue Dec 6 2016/

Good low level moisture return this evening will spread stratus
northwestward, likely affecting KLBB and KPVW late tonight. IFR
conditions looking the most likely outcome. Veering of winds to
the west ahead of an arctic cold front should restore VFR
conditions by Wednesday afternoon.

PREV DISCUSSION... /issued 343 PM CST Tue Dec 6 2016/

Colder weather has settled in across the area and we will see
another reinforcing surge of arctic air on Wednesday. Surface
high pressure ridge is centered to our NE and is moving away as
winds respond to low pressure across Colorado. Broad cyclonic flow
to continue across the southern Conus with strong jet and flow of
Pacific moisture keeping mid and high clouds over the region.
Focus late tonight turns toward prospect of low stratus and
freezing fog as NAM...HRRR and RAP all indicating areas of
advection fog developing as low level warm moist advection
commences above cold surface temps. Not expecting significant
precipitation early Wednesday as moisture is very shallow so left
out mention for now. Low stratus/fog likely to lift by mid to late
morning as westerly surface winds increase ahead of next cold
surge in the late morning to early afternoon. Would normally
expect this type of front to be well ahead of schedule...and that
may happen but given shallow nature of front and cyclonic zonal
flow aloft...model timing may be pretty close. We are currently
expecting front into northern zones by noon to 1 pm...through
Lubbock by 1-3 pm...and clearing the remainder of the Rolling
Plains and southern South Plains by 5 pm. Leaned toward the lower
end of MOS guidance given nature of this modified Cp airmass.
Highs occurring early...then temps falling quickly toward sunset.

Only change of concern to the inherited long term package was to
introduce non-measurable wintry precip late Wed night into early
Thu following tomorrow`s strong FROPA. Model soundings are
trending more moist in the post-frontal regime with decent
saturated depths progged along the frontal inversion. Coldest
temps within this saturation are at -10C or warmer at times, so
some ice nucleation/snowflake development is possible. However,
muted ascent and dry air advection should limit any of this to
just light freezing drizzle and flurries before the stratus erodes
from N-S Thu afternoon. On that note, latest MAV is very stubborn
in clearing out clouds during the day, hence its highs only in the
upper 20s for Lubbock. Feel lower 30s is a safe bet for now given
some clearing and very dry air advecting south, which will set the
stage for another bout of chilly lows Fri morning.

Largely zonal upper pattern through late week will keep the chilly
surface ridge progressive and allow a nice recovery in max temps
by Sat, before another cold front becomes dislodged by a shortwave
trough to our north. GFS is more bullish with this wave than the
ECMWF and therefore is about 12 hours faster with the front. Not
inclined to bite on any one solution yet, but have nudged temps
cooler on Sun - somewhere between the chilly GFS and unseasonably
mild ECMWF. Thereafter, an even more significant cold wave looks
to be materializing given a southward dislodging of the Polar
vortex progged through the Canadian Prairies, with bitterly cold
air (850mb temps of -20C or colder) possibly overspreading a large
chunk of the Great Plains Mon-Tue.




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