Area Forecast Discussion
Issued by NWS

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FXUS64 KLUB 250503

Area Forecast Discussion
National Weather Service Lubbock TX
1203 AM CDT Sun Oct 25 2020

VFR conditions will prevail through at least 12Z at all terminals.
A cold front will begin to push through the region starting around
12Z. Conditions should initially stay VFR but could drop to MVFR
at CDS close to mid-day/15-16Z. VFR conditions are expected to
continue at LBB and PVW through 22-00Z before lowering to at least
MVFR. IFR is definitely not out of the question after 00Z at any
terminal, but confidence is not high enough to mention just yet.
Another monkey wrench in the gears is the possibility for precip
as well as precip mode after sunset. The onset of precip is likely
to be towards the end of this TAF cycle but could include a wintry
mix. This will be looked examined in more detail for the 12Z TAF


.PREV DISCUSSION... /issued 247 PM CDT Sat Oct 24 2020/


After a chilly start to the day, including the first freeze of the
season for both Lubbock and Childress, breezy southwesterly winds
and filtered sunshine have allowed temperatures to rebound nicely.
19Z temperatures are mostly in the 60s, and could briefly breach the
70s later this afternoon, primarily on the Caprock. The winds will
drop off this evening but maintain a southerly component, and it
will be much milder than this morning. Lows by Sunday morning will
range from the middle 40s to lower and middle 50s.

Attention will then turn north as a cold front will be plunging
southward across the High Plains. We have tended to favor the faster
guidance which brings the front into our northeastern zones near
daybreak, backdooring through much of the South Plains by 18Z, and
exiting our southwestern zones late afternoon or early evening.
Strong cold air advection and a blossoming stratus deck will follow
the FROPA. The timing of the front will make for a tricky
temperature forecast, with a large contrast from northeast to
southwest across the CWA. Temperatures may not make it out of the
50s or low 60s across the southern Texas Panhandle, while the
southwestern South Plains will likely make a quick run into the 80s
before dropping off late in the day. Gusty northerly/northeasterly
winds sustained at 15 to 25 mph will be common behind the front. The
risk for any light precipitation should hold off until Sunday



Sunday night behind the strong polar airmass/front a moist N/NE
surface flow will allow for precipitation to start falling across
the area as isentropic lift over the cold front occurs. As this is
occurring a jet streak aloft over the western U.S. will drop
southward and form a closed low over Arizona. A lull in
precipitation will occur Monday afternoon as the low continues to
dig over AZ and we wait for the better lift to get closer to the
area. By Tuesday morning the low will be over southern New Mexico
and far West Texas allowing PVA and divergent flow aloft to promote
widespread synoptic lift leading to area wide wintry precipitation.
Tuesday we will likely see wintry precipitation all day as the low
tracks along the TX/Mexico international border.

Wednesdays precipitation chances and p-type will be determined by
the track of the low, unfortunately this is where the models
diverge. The GFS pulls the low just south of the CWA and then
eastward while the ECMWF pulls the low diagonally through the CWA
and then NE. Both models hold onto our precipitation chances through
early Thursday thanks to wrap around moisture. At this point it is
too early to determine the track of the low, but the good news is
according to B.Lambert and his "Synoptic Climatology of Heavy Snow
in West Texas and Eastern New Mexico" study both tracks are still
favorable for winter precipitation across our area. Although this is
not a heavy snow event, we can deduce that the path for better
precipitation in our area would be the GFS scenario as the ECMWF
would favor the northern Texas Panhandle. Given the fact that the
models tend to struggle with this type of weather pattern we will
let the Blended PoPs stand until there is better model agreement.

Now to precipitation type and accumulations...precipitation type
remains the big question with this forecast. Profiles suggest that
across the NW South Plains and southwestern Texas Panhandle a mix of
snow and sleet will be favored, the central South Plains and Rolling
Plains will be a mix of sleet, freezing rain and rain while the SE
Rolling Plains will see a mix of rain and freezing rain. Timing and
track of the low will also determine accumulations. However, with
the better lift and some frontogenetical forcing present from the
Rolling Plains eastward it appears the highest precipitation amounts
will likely be off the Caprock. Ice accumulations will also be
highest off the Caprock where the better lift and warmer layer aloft
will be present. There is still a lot to analyze and refine in this
forecast over the coming days, but regardless it will be cold with
periods of wintry precipitation.

The upper low is expected to be east of the region Thursday with
drier and seasonable weather to follow.




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