DFW FORECAST DISCUSSION
811
FXUS64 KFWD 201112
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
512 AM CST Mon Jan 20 2020


.SHORT TERM... /NEW/
Update:
No major changes were made with this morning`s short term forecast
issuance, with the previous forecast still on track. Minor
adjustments were made to sky/temperature trends to account for the
band of cirrus draped across the I-20 corridor. These clouds have
allowed temperatures beneath it to stay about 5 degrees warmer
than surrounding sites as they inhibit outgoing radiation.
Otherwise, the rest of today/tonight`s forecast trends are in good
shape as outlined in the previous discussion below.

Previous Discussion:
/Through Tuesday/

A progressive shortwave trough is ushering some fast-moving
cirrus through the forecast area, which is temporarily hampering
radiational cooling. However, overcast skies should only last for
a few hours at any given location, and most of the area should
still have ample time for temperatures to fall to near or just
below freezing prior to sunrise. Despite its intensity, passing
cirrus will be all that this shortwave can muster due to an
absence of any meaningful moisture. Following this morning`s cloud
cover, mostly clear skies will resume today with light winds.
Another day of near-normal highs will be the result for the MLK JR
Day holiday.

With dry air remaining in place, overnight lows will be capable
of dropping to within a few degrees of the freezing mark once
again despite the return of light southerly winds. By daybreak
Tuesday, a weak backdoor frontal boundary will nudge into parts of
northeastern Texas, briefly resulting in some weak CAA and light
NE winds. This may allow temperatures to fall into the upper 20s
for lows across our far northeast zones.

Later Tuesday morning, the aforementioned boundary will quickly
wash out as all winds return to the southeast. Modest warm
advection during the day should allow highs to reach the mid 40s
to mid 50s despite a gradual increase in mid-level cloud cover
from the west. Mid and upper level moisture will spread eastward
over the entire CWA within a strong belt of westerlies associated
with an approaching upper trough. As a result, most of the area
should be overcast by the afternoon. As some top-down saturation
occurs, virga may begin falling across some of our western zones,
with some light precipitation possibly beginning to reach the
ground late in the afternoon. The more widespread rainfall will
begin later on, and this potential is addressed in the long term
portion of the forecast.

-Stalley

&&

.LONG TERM... /Issued 216 AM CST Mon Jan 20 2020/
/Tuesday through Next Weekend/

A wet/cool weather pattern is shaping up mid-week and beyond
across North and Central Texas. Rain chances will start to ramp up
late Tuesday into Wednesday, with a potential for a wintry mix for
parts of Northeast Texas. Instability builds some late Wednesday
into Thursday and while a few thunderstorms are forecast, severe
weather looks unlikely at this time. Drier conditions can be
expected Friday and into the last weekend of January.

The temperature forecast on Tuesday remains difficult as a
backdoor front is expected to slide through at least parts of the
area late Monday into Tuesday. I`ll side with some of the cooler
guidance as current upstream observations across the Ozarks
indicate some pretty shallow/cold air. While some modification of
this airmass is likely, it still appears like that it`ll remain
pretty chilly as this shallow airmass invades from the northeast.
As is *usually* the case with these shallow cold air intrusions,
global guidance struggles with the speed of its forward progress.
I`ve trended toward cooler conditions north of US HWY 380 in line
closer to NAM/WRF guidance for Tuesday and Wednesday`s high
temperatures. If the cold air upstream really modifies, the
current forecast will need to be altered to reflect much warmer
conditions north of US HWY 380. This would also have ramifications
for the p-type on Wednesday morning. For now, highs in the low to
mid 40s north of this boundary are expected, with low 50s
elsewhere.

Ascent atop this cooler airmass is expected to commence late
Tuesday night into Wednesday. Initial precipitation will be light
as there will be a substantial amount of dry air to overcome. Top
down moistening will be first to occur west of US HWY 281 where
low level thermal profiles should support largely a very cold
rain. Farther east across North Texas (toward the I-35 corridor),
there will be a brief window in which moistening thermal profiles
may support a rain/light snow/light sleet mix. This potential
looks very low and for now, I`ll leave out of the forecast. The
best chance for a wintry mix will be for locations near and
northeast of a Sherman/Denison to Sulphur Springs line. Given the
run-to-run consistency of the colder model guidance and most
probable area of coldest air/most favorable thermal profiles, I
will continue to mention a wintry mix (light rain, light snow and
light sleet) across Northeast Texas.

Regarding any snow/sleet accumulation, some SREF members (though
largely based off of the colder NAM) indicate that up to 1/2 inch
of snow/sleet may fall. While not out of the realm of
possibility, this likely represents the worse case scenario. I do
believe that the potential exits for minor accumulation of
snow/sleet (mainly a light dusting) on mainly grassy surface,
however, I don`t expect major travel impacts at this time.
Moreover, the increasing WAA regime should foster an eventual
transition to just a cold rain by Wednesday afternoon. PoPs on
Wednesday will range between 60 and 80 percent range, with the
best rain/precipitation chances north of I-20 where large scale
ascent will be maximized ahead of the first shortwave trough that
will graze the area. Wednesday will be a pretty raw day with
temperatures mainly in the 40s. A few low 50s are possible across
the Big Country. If NAM guidance is to verify, however,
temperatures may remain in the low 40s area-wide.

There may be a slight lull in precipitation late Wednesday into
Thursday, but this should be short lived as the next upper trough
(a little deeper than its predecessor) will arrive from West
Texas. This should induce surface cyclogenesis upstream and result
in a stronger WAA regime (thus why temperatures on Thursday are
greater than Wednesday). The stronger southerly flow will help to
boost surface moisture and contribute to building instability. As
such, a mention of isolated thunderstorms remains in the worded
forecast, though little in the way of severe weather is
anticipated. Rain amounts will be a little heftier on Thursday,
especially across East Texas thanks to the added convective
element of precipitation. Any convective rainfall may exacerbate
any remnant creek, stream or river flooding. Rain should taper off
through the day on Thursday and by Friday morning, I expect that
most areas will be rain/storm-free as a front will sweep through
the area.

The last weekend of January appears largely dry as a less humid
airmass invades from the north. This will mean that we`ll have to
contend with cold mornings (lows in the 30s) with pretty pleasant
afternoons (highs in the 60s and possibly 70s).


Bain

&&

.AVIATION... /NEW/
/12z TAFs/

VFR will prevail through the next 24-30 hours. Winds will
generally be light and variable through mid or late afternoon with
a diffuse surface pattern in place. However, by this evening, a
light prevailing southeasterly breeze should begin which will
continue into Tuesday. Otherwise, sky conditions will consist of
some passing cirrus through this morning before clearer skies
prevail this afternoon. On Tuesday, widespread mid and high cloud
cover will begin spilling in from the west, and VFR cigs around
10-15 kft will arrive towards the very end of the TAF period.

-Stalley

&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    54  33  49  36  45 /   0   0   5  80  80
Waco                55  31  55  35  48 /   0   0   5  70  70
Paris               50  30  42  33  39 /   0   0   0  50  80
Denton              53  32  48  38  45 /   0   0   5  80  80
McKinney            52  31  46  37  43 /   0   0   0  80  80
Dallas              54  33  50  38  45 /   0   0   0  80  80
Terrell             53  31  49  37  44 /   0   0   0  70  80
Corsicana           54  33  54  38  46 /   0   0   0  60  80
Temple              55  36  57  39  49 /   0   0   5  70  70
Mineral Wells       55  33  51  38  48 /   0   0  10  80  60

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

26/24

NWS FWD Office Area Forecast Discussion