Area Forecast Discussion
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FXUS64 KLUB 172354
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
554 PM CST Fri Feb 17 2017

.AVIATION...
Winds will quickly drop off this evening and be somewhat variable
as a surface low sags southeastward across northwest Texas. KLBB
and KPVW will remain VFR through Saturday with only a few mid-high
clouds at time. As the surface low traverses the Rolling Plains
it may draw enough moisture around it to bring a risk of low
clouds and/or fog near KCDS around daybreak Saturday. It is
unclear if the sub-VFR conditions will make it into the terminal
or halt just to the east. Given the uncertainty, did insert a
TEMPO group reflecting MVFR conditions at KCDS from 12-16Z,
though IFR or even LIFR could potentially affect the terminal.

&&

.PREV DISCUSSION... /issued 403 PM CST Fri Feb 17 2017/

SHORT TERM...
Regional METARs and mesonets at 3 PM captured a surface low with a
closed circulation south of Vega - largely a reflection of a 700 mb
low immediately aloft. These lows are lagging a separate upper low
now analyzed in far SW Oklahoma, but by tonight the surface low and
attendant surface trough in its wake will crawl SE into the Rolling
Plains, before eventually stalling and dissolving early Sat morning.
Until then, a corridor of stronger westerly winds near 20 mph across
our SW zones along with RH values in the teens will prolong some
marginal wildfire conditions in these areas before winds decouple
toward 6 PM.

Concern tonight is for some advection fog and/or stratus to develop
within a fetch of moist E-NE winds north of the surface low,
primarily along the Red River extending into Childress and Cottle
Counties. Dewpoints already in the 40s across OK and northwest TX
should have little problem supporting some fog development as temps
cool sufficiently under clear skies. Farther west, the challenge
concerns the arrival of periodic mid and high clouds as a dirty
ridge exits NM. Latest satellite presentation of these clouds
appears quite opaque which could easily hold Saturday`s high temps
back a bit from the mildest MOS values. Opted to keep high temps on
the cooler end of guidance, particularly with a slow moistening of
SE winds region wide ahead of Sunday`s upper trough and dryline.

LONG TERM...
The features of interest in the long term continue to be Sunday`s
southern stream shortwave and Thursday`s High Plains
cyclogenesis/wind event. In summary have kept high chance POPs off
the Caprock Sunday but lowered to slight chance further west. Also
went above guidance values for temps and winds Wednesday and
Thursday with potential for significant wildfire spread given
pattern.

For the details of each...The thermodynamics associated with Sundays
trough continue to look promising for isolated to scattered
thunderstorms primarily off the Caprock. The 12Z and 18Z runs continue
to indicate a sharpening dryline during the afternoon with
strongly veering winds and drying atmosphere across much of the
area. Strong southerly flow in advance of the nearly neutral upper trough
continues to suggest decent moisture advection with PWAT values
nearing 1/2" at KLBB and 1" at KCDS. Warm advection and low level
lift could be enough for some light showers or drizzle in
saturated low levels so have included mention of patchy fog and
showers prior to sunrise. Details for the afternoon will likely
remain hidden in the mesoscale until we get a bit closer to the
event but models show a bulging dryline feature with some
convection breaking out in the Panhandle by late afternoon with
the dryline bending back northwest as stronger northern piece of
energy helps deepen a surface low in southeast Colorado.

Instability axis with CAPE values of a few hundred J/kg could hang
on long enough for the far northern Rolling Plains and southeast
Texas Pnhdl to be threatened by a strong to severe cell with a
hail or high wind threat before activity quickly moves into
southwest OK and northwest TX. Behind the dryline, expect breezy
southwesterly winds to develop with clouds keeping temperatures in
the 60s despite a very mild start to the day. The warming trend
will be muted some behind the strong Pacific front on Monday.
Expect daytime highs to get a nice bump on Wed as southwesterly
flow develops ahead of next storm system digging across the
central Rockies. Blended guidance looked a bit low on temperatures
and winds on Wednesday given the pattern of strengthening
downslope winds and emerging thermal ridge with increased
thickness values.

The biggest impact event next week will be the potential for
significant fire weather conditions on Thursday. Secondary surface
cyclogenesis occurs across the northern Panhandle as a 100kt plus
mid level jet emerges across the Permian Basin. Dry surface air
will advect eastward underneath a strong thermal ridge which all
could combine temporally to support rapid wildfire spread in the
afternoon across portions of the southern High Plains. With
likely more limited wetting from Sunday`s storm system and a
fairly prolonged above normal temperature the drying potential
ahead of Thursday`s system, the priming of lighter fuels will be
a concern.

&&

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

$$

99/99/23


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