NWS Area Forecast Discussion

FXUS64 KFWD 181132

Area Forecast Discussion
National Weather Service Fort Worth TX
532 AM CST Mon Jan 18 2021

...New Short Term, Aviation...

Low level winds have turned to the south but still remain fairly
light at less than 10 MPH. They are still expected to increase mid
to late morning to 10-20 MPH ahead of our next front, which is
still slated to push slowly through the area tonight into Tuesday.
After a nice day today, the aforementioned front will be the
beginning of a more unsettled weather pattern for the rest of the
week. More details are contained in the below discussions.


Previous Discussion:
/Through Tuesday/

A surface ridge is currently passing east through the area, and
local winds should all eventually shift to the south as the ridge
axis exits to the east during the overnight hours. Calm to light
winds in the meantime have allowed for good radiational cooling
conditions due to the dry airmass and clear skies in place.
Widespread temperatures in the 30s with rural and valley locations
in the 20s can be expected as a result through early morning.

South winds will increase fairly rapidly mid to late Monday
morning as lee-side troughing strengthens ahead of a couple of
upstream disturbances. In fact 925 mb flow will quickly veer and
jump to 30-40 MPH in the hours around daybreak. This will usher in
some low clouds during the day, but there should be enough sun to
allow temperatures to climb into the 60s by afternoon.

Back to the upstream systems...one a shortwave over Saskatchewan
and the other a developing upper low off the West Coast. The
shortwave is progged to race southeast through the Northern Plains
over the next 24 hours, helping to push the next cold front
southward towards and eventually through North and Central Texas.
The front should be on the doorstep of the northwest counties by
Monday evening around sunset, along the I-20 corridor 9 PM to
midnight, push slowly south into Central Texas overnight and
eventually through the southern-most zones sometime Tuesday
morning. Scattered showers will be possible along the front, with
the best chances being east of I-35 and south of I-20 where
slightly better moisture will be in place. Also, it appears that a
disturbance emanating from the deepening low out west will move
east across Central Texas on Tuesday, enhancing lift just north of
the boundary, hence the high POPs continuing through the day.

Despite the presence of the front and the passing disturbance,
limited moisture should keep the early week rainfall amounts at a
half inch or less for the most part, with areas west of I-35
possibly missing out entirely. Either way, it should be quite a
bit cooler across the board behind the front with Tuesday highs
remaining in the 40s and 50s.



.LONG TERM... /Issued 354 AM CST Mon Jan 18 2021/
/Wednesday Through Next Weekend/

The upper trough currently deepening along the West Coast will set
up a southwest flow regime across the Lone Star State that will
maintain an extended period of unsettled weather. Even after the
trough dampens as it ejects into the Plains late in the week, it
will be quickly replaced by another West Coast trough during the
upcoming weekend. While continuous rainfall is not expected,
persistent cloud cover will maintain gloomy (though not
particularly cold) weather.

The initial rain event accompanying Tuesday`s cold front may
linger into early Wednesday within portions of Central and East
Texas where overrunning will continue in the wake of a departing
upper disturbance. The rain-free interlude deeper into the cold
air will be short-lived as the surface front rapidly retreats
during the day Wednesday. A reinforcing surge of low-level Gulf
moisture will coincide with a slug of mid-level moisture/lift
from the Pacific late Wednesday into Wednesday night. The
resulting rain event will be primarily focused within our
southern and eastern zones where extraordinary precipitable water
values may yield periods of heavy rainfall. Coming on the heels of
a round of rainfall just 24 hours earlier, this period will need
to be monitored for the potential for short-fuse hydrologic

Although Thursday and Friday may be a relative lull in the
rainfall, anomalously rich moisture will remain across Central and
East Texas where low-end PoPs will linger. The shearing trough
will likely transit to our north on Friday, its passage
encouraging a weak frontal intrusion at the surface. While this
could enhance rain chances, the frontal forcing and the mid-level
lift appear to be mistimed. The next upper trough will remain
connected to the polar flow, having a greater impact on the
downstream flow regime. As a result, more significant rain
chances (and potential flooding concerns) will return Saturday and
Sunday as more intense southwest flow ensues.



/12Z TAFs/

Light southerly winds should increase to around 15 kt later this
morning as the next front approaches. Winds have already increased
a few thousand feet off the surface, which has led to rapid
development of IFR/MVFR cigs over the Hill Country. Low clouds
will spread northeast into the area over the next several hours,
reaching KACT around 14Z and the DFW Metro area 16-18Z. That said,
cloud bases will likely increase the farther north the stratus
gets, so the current expectation is that cigs will not be as low
as they are to the south. Some recent guidance does, however,
indicate some MVFR reaching Waco this morning and the Metroplex
prior to midday, so the latest forecasts will contain a TEMPO MVFR
group for a few hours.

These clouds will shift off to the northeast late afternoon, but
more widespread MVFR will develop this evening as the cold front
approaches. FROPA and the onset of MVFR/VCSH still sits at 19/04Z
for the Metroplex. The front will slow as it approaches Waco, and
IFR conditions will likely develop as the front draws near. FROPA
and the onset of IFR/VCSH at KACT is 19/09Z.



Dallas-Ft. Worth    64  46  51  41  54 /   0  30  40  30  30
Waco                66  51  54  44  55 /   0  50  80  60  40
Paris               61  43  51  39  53 /   0  60  40  20  30
Denton              65  43  51  38  55 /   0  30  20  20  30
McKinney            63  45  51  39  54 /   0  50  40  20  30
Dallas              65  48  52  43  55 /   0  40  40  30  30
Terrell             64  49  52  40  54 /   0  50  60  40  30
Corsicana           65  50  55  45  55 /   0  50  70  50  40
Temple              67  53  55  43  54 /   0  50  80  60  40
Mineral Wells       68  44  50  37  53 /   0  10  20  20  30




NWS FWD Office Area Forecast Discussion