Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/10/23

Area Forecast Discussion

National Weather Service Lubbock TX

 1004 PM CST Sat Dec 9 2023

...New AVIATION...

.SHORT TERM...
(This evening through Sunday)
Issued at 207 PM CST Sat Dec 9 2023

A trough is situated across the central CONUS this afternoon with
ridging aligned roughly with the east and west coasts.  A
progressive pattern will persist with the trough making its way over
to the east coast by tomorrow evening.  This will leave northwest
flow aloft across our part of the country.

This afternoon has been a bit tricky on precipitation and clouds.
While visible on webcams, amounts have remained at a trace or less
and wet bulb cooling has continued to aid in snowfall production
across the northern row of counties.  Elsewhere, sprinkles to
perhaps a few light rain showers, should slowly dissipate through
the afternoon with skies clearing along with diminishing wind
speeds.

The H3 jet is rather sharply curved and will place us in the
subsident side of the trough bringing a return to fair weather for
Sunday with mostly clear skies.  Breezy conditions will return
during the afternoon making for elevated fire weather concerns in
the SWRN TX Panhandle.

&&

.LONG TERM...
(Sunday night through next Friday)
Issued at 207 PM CST Sat Dec 9 2023

The progressive upper air pattern that has been affecting the CWA
over the last few days is forecast to shift northward into central
Canada as an anticyclonic wave break occurs over the northeastern
Pacific Ocean early next week, and a distinct pattern change will
follow heading into mid-week. On Monday, the CWA will be positioned
beneath quasi-zonal flow as an attenuated shortwave trough pivots
over central Mexico, and as the subtropical and polar jet streams
phase over the eastern two-thirds of the nation. At the surface, the
western periphery of a strong anticyclone over the Deep South will
eclipse the CWA, with an expectation for temperatures to moderate
back into the lower 60s area-wide as mixing heights are shunted
beneath the belt of westerly flow at 700 mb and above. Northeasterly
winds will gradually shift to the east throughout the day and
continue to veer southward overnight into Tuesday as surface
troughing becomes re-established across the western High Plains.
Cloud cover in the mid- and upper-levels will increase heading into
the morning hours Tuesday as steering flow backs to the southwest,
which will result in low temperatures being a few degrees warmer
than Monday morning.

Further west, global NWP guidance is in excellent agreement with a
train of PV streamers to traverse eastward over the northern waters
of the Pacific Ocean, with the leading PV anomaly moving onshore the
west coast of the U.S. on Monday and propagating southeastward into
the southern Great Basin. These features are currently evident on
GOES-West water vapor imagery over the northern waters of the
Pacific, which bolsters confidence in this prognostication. A
larger, more-pronounced PV anomaly is also forecast to rotate into
the northern Pacific Ocean from the Arctic region on Monday,
modulating the amplitude of the subtropical ridge off the western
U.S. coastline. This will cause an anticyclonic wave break over the
northeastern Pacific Basin and into western Canada, resulting in a
positive feedback that will strengthen the PV anomaly over the
southern Great Basin heading into mid-week. A closed, and possibly
cut-off, mid-level cyclone is forecast to form over the Four Corners
region by Wednesday following the breaking wave event, which will
shift the polar jet stream northward into central Canada; and
depending how far north the jet stream shifts will dictate if the
aforementioned low can become cut-off from the synoptic background
flow (all cut-off systems are closed, but not all closed systems are
cut-off).

A wavy surface pattern should be present west of the CWA with a
surface trough anchored across northern Mexico heading into Tuesday,
and with the net increase in large-scale forcing for ascent aloft,
southeasterly winds will become breezy area-wide on Tuesday beneath
a dense overcast. The combination of adiabatic expansion from the
upslope flow component to the winds and limited diabatic heating
will garner much cooler temperatures during the afternoon hours.
Meanwhile, backed low-level/850 mb flow in response to the
geopotential height falls associated with the deepening cyclone to
the west will advect a plume of anomalously high precipitable water
(PWAT) content for this time of year northward from the western Gulf
of Mexico. For context, NAEFS is indicating PWAT content between 2-3
standard deviations above normal by Wednesday. This, combined with
increasing high-level difluence as a mid- and high-level jet streak
nearing 50 kt and 70 kt, respectively, round the base of the trough
in congruence with a 300 mb subtropical jet streak translating over
north-central Mexico, is forecast to galvanize a widespread
precipitation event on Wednesday into Thursday. There remains some
discrepancies with respect to the exact position of the 500 mb low
by this time frame; however, a backed low-level jet should also be
intact over the CWA where the advection of IVT values ranging
between 200-300 kg/m/s will be possible. Locally heavy rain may
occur, particularly with any thunderstorms embedded within the
larger rain shield, on Wednesday into early Thursday.

The eastward progression of the closed low will be slow, especially
as the polar jet stream is displaced over 1,000 miles to the north
of the low as it rotates towards the CWA heading into Thursday (and,
hence, the indication of it possibly becoming cut-off). A prolonged
precipitation event is forecast, with a changeover to a wintry mix
during the overnight hours Wednesday into Thursday as the columns
aloft become supersaturated with respect to ice and surface
temperatures fall near or below freezing across portions of the
Caprock. It is unclear on how much snow accumulation there will be
at this time; however, snow-to-liquid ratios (SLR) will be low/less
than the standard 10:1 SLR with a more-slushy type of snow forecast
as 850 mb temperatures hover around 0 deg C (i.e., a warm nose that
melts the heavier snow falling at commercial aircraft altitude). Any
snowfall that does occur will melt on Thursday as temperatures rise
into the lower 40s, with a secondary transition into a steady, cold
rain area-wide as the mid-level cyclone rotates towards the Big Bend
region Thursday night. A tertiary transition in precipitation-type
will follow heading into early Friday morning, with another round of
wintry mix possible across portions of the Caprock before the system
begins to exit the region.

PoPs for this mid-week system have increased from the previous
forecast assessment, and confidence in this event coming to fruition
continues to increase. Exact details will become better-refined over
the next few days as NWP guidance is able to ingest more in-situ and
satellite data, but the forecast evolution at the synoptic-scale
over the western and central U.S. leans towards a Lambert B pattern,
which is notorious for producing precipitation events over West
Texas. Towards the end of next week, global NWP guidance begins to
diverge on how soon the closed feature transitions into an open
wave. Regardless, rain is forecast to wane in coverage by early
Friday as the base of the trough pivots east of the CWA and as a
cold front moves through the region. Cooler and drier weather are
forecast thereafter heading into next weekend.

Sincavage

&&

.AVIATION...
(06Z TAFS)
Issued at 1000 PM CST Sat Dec 9 2023

Light winds will persist overnight, before increasing Sunday
morning out of the southwest with gusts up to 25 kts possible.
These are expected to diminish around sunset. Mostly clear skies
will continue through the TAF period.

&&

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

$$

SHORT TERM...26
LONG TERM....09
AVIATION...19