Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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000
FXUS64 KFWD 111306
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
706 AM CST Sun Feb 11 2018


.MESOSCALE UPDATE...

/Concerning band of precipitation moving into Eastland-Erath-
Comanche Counties over the next 90 minutes/

Radar imagery from DYX/FWS shows enhanced reflectivity aloft with
a band of elevated showers and thunderstorms currently over
Coleman/Brown counties. Over the last 30 minutes, lightning data
indicates several cloud to ground strikes with more in-cloud
lightning activity. These cells are persisting in an area of
strong isentropic ascent with steep lapse rates and elevated
instability on the order of 200-400 j/kg and should continue to
move northeast over the next 90 minutes. Precipitation rates will
be considerably heavier in these cells than much of the activity
that is already ongoing. A mix of moderate to heavy freezing rain
and/or sleet can be expected. With temperatures in the low to mid
20s from Comanche to Eastland to Stephenville, any liquid
precipitation would quickly freeze resulting in localized ice
accumulations up to 1/10 of an inch in a short period of time.
This would be sufficient to cause problems not only on elevated
surfaces and bridges, but also most main roads. The cells are
moving to the northeast at 40-45 mph.

Farther north, several reports of light sleet or freezing rain
have been received. Precipitation rates remain sufficiently light
at this time to inhibit more significant impacts. Strong north
winds and dry near surface air will help quickly evaporate lighter
precipitation making it to the surface.

Dunn

&&


.AVIATION... /Issued 557 AM CST Sun Feb 11 2018/
/12Z TAFS/

MVFR conditions generally prevail across North Texas this morning
with north winds 15-20 kt. The main concern through the next
several hours will be the potential for some light freezing rain
or sleet as a band of mid level forcing spreads across North
Texas. Area radar imagery already shows scattered elevated
convection from near Fort Worth extending back southwest to San
Angelo. This is streaming northeast across the area and this trend
should continue through midday. There is some very dry air beneath
the cloud deck where the precipitation is occurring, so some
evaporation is occurring before some of this makes it to the
ground. We`ll keep a TEMPO for some -FZRAPL through the late
morning hours, although no significant accumulations are expected.
Some very light accumulations of ice or sleet can be expected
through late morning before temperatures warm above freezing
during the early afternoon hours. Cigs should improve to VFR by
midday with continued lifting through the afternoon hours.

At Waco, similar trends with respect to cigs can be expected
although now it is looking more likely that the heavier
precipitation will remain to the north. We`ve removed the freezing
rain and sleet mention from the Waco TAF.

All precipitation will come to an end by early afternoon with VFR
conditions prevailing this evening and tonight.

Dunn

&&

.SHORT TERM... /Issued 331 AM CST Sun Feb 11 2018/
/Today and Tonight/

A reinforcing shot of colder air moved into North Texas shortly
after midnight accompanied by stronger north winds and
temperatures falling into the lower 20s. Most of North and Central
Texas is now below freezing with the exception of our far southern
counties, but these areas too will fall to below freezing over the
next few hours. Extensive cloud cover persists across the region
as warm moist air lifts up and over the colder surface airmass.

Our main concern for today will be the potential for some light
freezing rain and sleet as mid level forcing for ascent spreads
across North Texas. The air above the frontal layer remains fairly
dry, but low and mid level water vapor imagery shows some
increased moisture streaming in across Northern Mexico into the
Big Bend region and into west-central Texas this morning. Later
this morning, as the main trough axis swings into the Texas
Panhandle, isentropic ascent in the 800-600mb layer will really
increase across Central and North Texas. While the forcing is
quite strong, moisture availability will remain marginal at best.
Normally, this wouldn`t be of any significant concern, however
given the strength of the forcing within an area of steep lapse
rates (>7.5 C/km), parcels that do saturate can quickly become
buoyant resulting in convection. The strong ascent tends to find
the moisture if there is any available. Over the last hour, we
have seen some indication of this occurring to the west of San
Angelo where spotty convection is now apparent on radar. As this
forcing spreads eastward, it is likely that there will be at least
some scattered convective cells that develop across parts of North
Texas. That being the case, precipitation type should either be
freezing rain or sleet given the extensive warm nose above the
surface. If the convection is strong enough, then sleet would
probably be favored, but if it generally lighter, then the warm
nose would likely melt everything with only limited time for
refreezing. This would support more of a freezing rain scenario
given the surface temperatures in the upper 20s. Either way, there
is some potential for icing especially on bridges and overpasses.
Any heavier bursts of rain/sleet could cause some localized higher
impacts.

Concerning the advisory...we have decided to trim a good chunk off
of the Winter Weather Advisory with this issuance. Our northwest
and Red River counties will likely miss out on any precipitation
given that deeper colder and drier air is in place and the best
forcing should spread to the south. In our northeast counties,
some light freezing drizzle earlier yesterday evening has come to
an end and visibilities have improved with drier air moving in.
Any additional precipitation later today should occur as
temperatures rise to or just above freezing. This should mitigate
any impacts in this area. We`ll keep the advisory from the
Metroplex southwest to Eastland/Mills/Bell counties.

All of this precipitation should come to an end later this
afternoon with skies clearing this evening. It will be another
cold night with temperatures in the lower 20s northwest to lower
30s in the southeast.

Dunn

&&

.LONG TERM... /Issued 331 AM CST Sun Feb 11 2018/
/Monday Onward/

A cool and dry Monday will be in store as skies clear temporarily
while winds come around to the east and southeast. The glimpse of
sunshine will be short-lived, however, as moisture will be quick
to return late Monday into Tuesday. This resultant blanket of
stratus should keep temperatures on the warmer side Monday night
with most areas holding above freezing. The warmer start to
Tuesday and increased southerly flow/warm advection will cause
temperatures to climb into the 50s or low 60s during the day
despite cloudy skies. Some light rain or drizzle due to low-level
ascent may also occur mostly east of I-35 throughout the day.

The sun will remain scarce through the middle of the week as rich
low-level moisture and resultant low clouds continue to stream
northward. Some higher rain chances will occur on Tuesday night
into Wednesday as ascent from low-level warm advection increases.
The GFS and ECMWF have flip-flopped from yesterday`s solution, and
now the ECMWF is the wetter of the models through this time
period. Have maintained PoPs around 30-40% and hopefully guidance
will come into better agreement on rainfall potential in the next
couple of days. In addition, because of the increased warm
advection, temperatures will be several degrees higher on
Wednesday. Highs in the 60s or low 70s will be likely as
dewpoints climb into the 50s and low 60s. This will also mean a
warm and humid Wednesday night with low temperatures only falling
into the low 60s or upper 50s.

Thursday should be the warmest day of the week prior to the
arrival of another cold front late Thursday night or Friday
morning. Depending on the front`s arrival time, some pre-frontal
warming could see high temperatures climb to 75-80 degrees
Thursday afternoon. Rain chances will also accompany this front
and they will be on the increase heading into Friday and through
the weekend. However, there is still much disagreement on handling
the shortwave that will be responsible for these conditions. The
ECMWF maintains a much more open wave while the GFS keeps the low
cutoff for an extra day. However, both of these solutions are
trending more progressive over the past couple of runs. As a
result, will go with some 30-50% PoPs Friday into the weekend,
which at this point looks like a cold rain with temperatures
mostly in the 40s.

-Stalley

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    40  28  53  42  57 /  30   0   0   5  20
Waco                40  24  54  43  58 /  40   0   5  10  20
Paris               40  25  51  36  54 /  10   5   5   5  20
Denton              39  22  51  37  56 /  20   0   0   5  10
McKinney            40  23  50  38  55 /  20   0   0   5  20
Dallas              41  28  53  42  57 /  30   0   0   5  20
Terrell             40  27  52  39  57 /  30   5   0  10  20
Corsicana           39  29  52  44  56 /  30   5   5  10  30
Temple              39  28  54  43  58 /  30   0   5  10  20
Mineral Wells       39  23  52  37  58 /  20   0   0   5  10

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST today for TXZ116>119-
129>134-141>145-156>159.

&&

$$



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