FXUS64 KLUB 250907

Area Forecast Discussion
National Weather Service Lubbock TX
407 AM CDT Sun Aug 25 2019

The heat grabs the headlines to kick off this forecast. A Heat
Advisory has been posted for the southern and central South Plains
that afternoon and evening, where temperatures will peak around 105
degrees. The good news, if there is any (which there really isn't),
is that it will be a dry heat. Tomorrow will be even hotter before a
cold front brings more reasonable temperatures to the region.

Before we jump into the gory details, a look at the synoptic scale
features a shortwave trough grazing the region as it translates
through Kansas, while a flat but broad subtropical ridge is
beginning to extend out of the Desert Southwest into West Texas. The
shortwave was forcing a large MCS over Kansas, as well as additional
convection in central Oklahoma and even a few showers and storms
over the eastern Texas Panhandle. A little of this activity could
clip our far northeast CWA over the next few hours, but otherwise
lift from the disturbance will shift east of the area altogether.
Instead, the fairly benign looking upper ridge will help carry the
relatively dry air (for summer) sitting across central and northern
New Mexico into the South Plains. This dry air, with dewpoints
falling into the 40s and even 30s, coupled with weak downslope flow,
full insolation and 850 mb temperatures progged to climb to 33-35C,
all point to one HOT afternoon. Highs will be near 105 degrees over
roughly the southern half of the FA, ranging on the cool side to 100
or 101 degrees over the southwest Texas Panhandle. Given this, we
have issued a Heat Advisory for those counties on the Caprock where
highs will be AOA 105 degrees (the heat advisory criteria in the
Rolling Plains is 110 degrees, of which they should come up several
degrees short).

Unfortunately, Monday will be even hotter as compressional warming
ahead of a cold front drives temperatures even higher. It does look
like most of our area will need a heat advisory Monday afternoon,
and the southern South Plains could even flirt with excessive heat
warning criteria (110 degrees on the Caprock). We've deferred on
issuing a Excessive Heat Watch at this point, but do allude to the
possibility in the current Heat Advisory product. These
temperatures will threaten (or break) records today, and will
inevitably break records tomorrow.

After the two scorching days, a broad trough/low maturing over the
Upper Midwest into south-central Canada will send relief, in the
form of a cold front, our way. The latest round of NWP bring the
front through the South Plains Monday evening/night. The initial
FROPA should be a dry one given strong capping and meager pre-
frontal moisture, but post-frontal stratus may fill in over much of
the area. There are difference on how fast this stratus
thins/scatters on Tuesday, which will have impacts on highs, but
regardless, temperatures should drop 15+ degrees at most locations.

Persistent post-frontal upslope flow combined with a brief period of
northwest flow aloft will provide a decent shot of convection,
perhaps a widespread MCS if we luck out, Tuesday night or early
Wednesday. Low rain chances could linger into late week as a
fragmented monsoon plume bends this way, but hotter conditions
are the better bet as the frontal zone lifts northward and the
upper ridge noses back this way. After that, it does look like our
next cold front could move in sometime next weekend (as early as
Friday night or as late as Saturday night), complete with cooler
temperatures and improved rain chances.


Heat Advisory from 1 PM this afternoon to 8 PM CDT this evening
for TXZ033>036-039>042.



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