Area Forecast Discussion
Issued by NWS

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FXUS64 KLUB 102340

Area Forecast Discussion
National Weather Service Lubbock TX
540 PM CST Sat Mar 10 2018

Main point of concern is a cold front that will move through the
terminals late this evening with gusty NNE winds in its wake
(sustained at 20-25 knots with higher gusts). This front could
initially kick up a little BLDU and a brief period of MVFR cigs is
not completely out of the question behind the front, though
confidence in any sustained sub-VFR conditions is too low to
include in the TAFs. The northerly winds will slowly decrease
through the day Sunday with plenty of mid-high clouds holding


.PREV DISCUSSION... /issued 205 PM CST Sat Mar 10 2018/

An elongated surface trough was found bisecting the area from NW
to SE this afternoon complete with anomalous warmth running nearly
15 degrees above climo in many locales. This trough will be replaced
by stout surface ridging tonight through Sunday following a swift
cold frontal passage tonight ahead of NE winds of 20 to 30 mph.
Departure of the strongest pressure rises by daybreak Sunday will
precede a slow decline in winds through the morning and afternoon.

The main challenges behind tonight`s front involve how much low
level moisture recovery will ensue (compared to our arid pre-
frontal environment at present), how long this moisture can
persist through Sunday, and how the inevitable return of drier air
within the surface ridge will affect top-down saturation through
the day. This saturation aloft will accompany a surge of Pacific
moisture arriving on a 90+ knot upper jet progged to track to our
south and southwest tomorrow. One concern we have is that models
are often too bullish with top-down saturation whilst underestimating
sub-cloud drying in what is often a drier surface ridge with time.
With this in mind, we have lowered the earlier PoPs by 5% or so
while restricting measurable precip to our far western zones for
Sunday. The best shot for some light rain may actually unfold later
Sunday afternoon with the arrival of a shearing/decaying mid-
level trough. However, further drying of the lower levels by this
time could result in this scenario being all virga. Even accounting
for the overly moist model soundings, thermal profiles would
still support some snowflakes at times given 90% or more of the
column residing below freezing, but mild 2-meter temps should keep
accumulations nil.

Return flow arrives on Monday in advance of a slow-moving, but
shallow upper ridge in westerly flow. Passage of this ridge o/a
Wednesday should restore drier and breezier SW flow to most of
the CWA complete with much milder thicknesses. Until this drier
air arrives, there could be opportunities for low clouds or fog
at times Tue or Wed morning as modified Gulf moisture advects
north. Otherwise, models have recently converged on this moisture
becoming displaced well to our east by late next week under
stronger WSW flow preceding a positively tilted and (mostly)
mediocre-looking upper trough for the weekend.

Despite wind speeds largely around 15 mph, the newest Red Flag
Warning criteria justifies maintaining at least a low-end critical
wildfire threat this afternoon for most areas on the Caprock. This
is due to ERC values at or above 70% collocated with RFTI values
of 3 to 6 (these are calculated from RH and wind). Winds speeds
will taper toward sunset before strong RH recoveries arrive
following a brisk cold front overnight with gusty NE winds.
Additional wildfire threats are not expected to return until late
next week following a cool and more moist pattern from Sunday
through Wednesday.


Red Flag Warning until 7 PM CST this evening for TXZ021-027>029-



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