Area Forecast Discussion
Issued by NWS

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FXUS64 KLUB 151104
AFDLUB

Area Forecast Discussion
National Weather Service Lubbock TX
604 AM CDT Sun Apr 15 2018

.AVIATION...
VFR will persist through the TAF period with light winds.

&&

.PREV DISCUSSION... /issued 258 AM CDT Sun Apr 15 2018/

DISCUSSION...
A chilly start this morning with near freezing temperatures
expected everywhere as weak surface ridge overhead. Southern
South Plains and southern Rolling Plains may not experience
widespread light freeze, but at least pockets likely will while
northern areas appear fairly likely to get the widespread light
freeze. Northwest flow aloft in advance of progressive weak upper
ridge axis passing east early Monday. Winds will bend back to the
southwest or south later today and tonight - speeds mostly under
10 mph making for a generally (subjectively) pleasant day.

Monday, then more-so Tuesday, will see increasing southwest flow
aloft in advance of a potent upper low pressure trough scraping
through the northern and central Rockies. Tightening height and
surface pressure gradients will lead to breezy or low-end windy
and warmer temperatures Monday, then outright windy and very warm
Tuesday and probably some amount of dust with wind speeds likely
near wind advisory levels. Strongest wind core appears will remain
across the northern Texas and Oklahoma Panhandles, this time.

A weak Pacific/Continental cold front system will pass Tuesday
night leaving Wednesday as another potentially light wind and
somewhat cooler day - back down to near normal - and there doesn`t
appear nearly enough cold air for a significant freeze risk.

Following another progressive upper ridge axis passing late
Wednesday, the next Pacific upper trough system is still looking
more amplified and further south pushing a notable height fall
pattern across the southwestern U.S. Thursday then into the
southern plains Friday. As in previous discussion, we still have
concerns about the overall quality of moisture return - especially
depth - as flow will back but maybe not enough to tap into deeper
subtropical moisture. But whatever moisture is pulled into the
southern high plains by late Thursday should be acted upon by
strong dynamic cooling and differential vorticity advection
validating continued chance of thunder centered Friday-ish.
Solutions still are about 18 hours apart on passage of the upper
low into the high plains early Saturday, GFS faster than ECMWF,
so grids retain a broader time-frame for precipitation chances
than will ultimately be reality. None-the-less, we have tapered
precipitation quicker on the back side as the courser resolution
ECMWF typically over-produces precipitation trailing into the dry
subsident air.

And then looking probably just dry and windy for Saturday, i.e.
back to normal. And if this pattern holds up, perhaps next Sunday
again will be another "down" day for wind and somewhat cooler;
i.e. subjectively nice. RMcQueen

FIRE WEATHER...
Two potential critical fire weather days ahead - starting Monday
with increasing low level south-southwest flow. Uncertain how much
moisture return through Rolling Plains may keep humidity higher
and wind speeds generally on the lower end of red flag criteria.
However, with ERC values holding in the lower to middle 90th
percentiles on the Caprock, and approaching 90th in the Rolling
Plains, along with forecast RFTI levels of 4 or 5, we have issued
a fire weather watch Monday afternoon into early evening favoring
areas on the Caprock and adjacent parts of the Rolling Plains just
off the Caprock.

Tuesday at this point appears outright windy again as another
strong upper low pulls across the northern/central Rockies into
the northern plains. Strongest wind core will be to our north but
solid wind flow will overly the thermal ridge axis/very warm or
hot temperatures, directly overhead. Widespread RFTI of 7 or 8
and some potential again for RFTI 9 eventually could lead to
consideration for extremely critical. Tuesday is still 5th into
6th forecast periods - pretty far out - but confidence is high
enough and threat significant enough to validate an early fire
weather watch issuance (for all areas) this morning as well.

Next threat for critical fire weather may be next Saturday. RMcQueen

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 9 AM CDT this morning for TXZ023>026-
028>044.

Fire Weather Watch from Tuesday morning through Tuesday evening
for TXZ021>044.

Fire Weather Watch from Monday afternoon through Monday evening
for TXZ021>025-027>031-033>036-039>042.

&&

$$

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