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

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KFWD 210034
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
634 PM CST Tue Feb 20 2018


.MESOSCALE UPDATE...

A strong cold front continues to make southward progress and is
located roughly from Comanche to Paris as of 6pm. Initially, some
drying should occur farther behind the front while showers and
thunderstorms continue immediately along and behind it. Areas
from Graham to Bowie have seen a marked decrease in rain coverage
in the last hour and this should generally be the trend for
locations more than ~50 miles behind the front. Temperatures in
these locations, however, have fallen to near freezing as shallow
arctic air continues to funnel down the southern Plains. At this
point, the current forecast temperatures and Advisory
configuration for potential freeing rain overnight still are on
track. We`ll continue to assess temperature trends in guidance
through the next several hours, but at this time, there is no
indication the Advisory needs to be expanded southeastward. After
about midnight, a stronger wave of ascent should pivot through
the upper trough to our west. Isentropic lift within the 650-750mb
layer along with steepening lapse rates of as much as 6-7 C/km
should support some convective rain showers where temperatures
will have fallen to near or perhaps just below freezing. With
100-300 J/kg of MUCAPE available in this area, can`t rule out some
thunder occurring as well. If convective freezing rain occurs
with temperatures in the upper 20s, bridges and overpasses will
quickly deteriorate overnight and into Wednesday morning.

To the east and south of the current Winter Weather Advisory,
temperatures are expected to remain just above freezing overnight.
The cold front will have cleared our southeastern counties by
midnight or shortly after. However, the threat for heavy rain and
some flooding will continue in these areas as activity
intensifies with the aforementioned wave of ascent. Much of the
forecast area has already received 1-2" of rain with isolated
spots closer to 3-4". As continued waves of rainfall arrive into
Wednesday, the threshold for flooding will be decreased due to
soils becoming saturated. Additional river flooding and isolated
instances of flash flooding will be the primary concern for these
areas.

-Stalley

&&


.AVIATION... /Issued 602 PM CST Tue Feb 20 2018/
/00Z TAFs/

Concerns...Shower and thunderstorm threat continues through the
period with low MVFR and IFR cigs. Potential for freezing rain in
the Metroplex overnight being closely monitored.

A cold front is blasting through the region, already having moved
through DFW and is on its way to Waco. Strong north winds of 15-20
kts with gusts up to 25 kts will continue through the day on
Wednesday, but should diminish late Wednesday afternoon.

A combination of ceilings between 500-1200 feet prevails across
the region. All locations are expected to prevail at these
ceilings through the night, with IFR expected for most of
Wednesday. After the front passes, the potential for thunder
diminishes but showers are expected to continue. There will
likely be temporary breaks overnight, but the chances for rain
remain high through the night. On Wednesday, another wave of
showers, potentially with isolated thunderstorms, is expected to
occur, but the extent of precipitation should be diminishing by
the late afternoon hours.

The Metroplex airports are currently outside of a Winter Weather
Advisory to the west and northwest of them, but with temperatures
potentially falling to 30-35 degrees, freezing rain may become a
threat late tonight and Wednesday morning. Outlying airports such
at KAFW may fall to 30-32 degrees by daybreak Wednesday. We are
closely monitoring temperatures behind the front now, and upcoming
TAFs may need a mention of -FZRA overnight into Wednesday
morning. IF freezing rain does occur, ice accumulations up to
0.10" may be possible, and overnight rainfall rates are likely to
vary between a tenth and quarter inch per hour.

JLDunn

&&

.SHORT TERM... /Issued 251 PM CST Tue Feb 20 2018/
/Tonight/

Multiple shortwaves continue to work their way around a parent
trough located across the Rockies, generating enough lift to
produce numerous showers and storms across the North and Central
Texas. The axis of heavier precipitation has thus far remained
over the western two-thirds of the forecast area. Convection is
currently beginning to become focused along a cold front currently
making its way into the northwestern zones. The axis of heavier
precipitation will shift to the southeast tonight as the front
pushes southeast through the forecast area. A few strong to
marginally severe storms will remain possible due to good shear
and modest instability, but the focus will shift to heavy rain and
possible flooding over the next 24 hours.

Another issue that we have been monitoring over the past few days
is the amount of cold air present behind the front. Judging by
upstream observations, it is one again appearing that the NAM has
done a better job depicting the cold air within the shallow arctic
airmass. The latest temperature forecast has leaned toward the
colder NAM, which indicates sub-freezing temperatures across the
northwest counties overnight and through most of the day
tomorrow. The threat for a switch-over to freezing rain is
looking more likely overnight and Wednesday for areas to the west
and northwest of the Dallas-Fort Worth Metroplex. A Winter Weather
Advisory has been issued for areas along and northwest of a line
from Gainesville to Weatherford to Eastland, where freezing rain
accumulations between a hundredth and a tenth of an inch will be
possible late tonight through Wednesday.


&&

.LONG TERM... /Issued 251 PM CST Tue Feb 20 2018/
/Wednesday through early next week/

Travel west on I-20, northwest on Highway 287 and north on
Interstate 35 could become difficult at times by midday Wednesday.
The advisory is set to expire at 6 PM Wednesday, but may need to
be extended if future trends suggest that cold air and precipitation
will linger beyond that time. In addition, if later guidance
trends colder farther south, we may see some minor impacts creep
into the Metroplex during the morning hours Wednesday. Will leave
it to the evening and overnight shifts to monitor temperatures
and adjust the advisory area if it becomes necessary.

Meanwhile, the cold front will continue sagging southeast,
reaching the southeastern counties by Wednesday afternoon. The
focus for the heaviest precipitation will likewise shift east of
I-35 and south of I-30. It may become necessary to remove western
counties from the Flash Flood Watch as the heavier precipitation
moves east. However, due to the presence of strong ascent
associated with the Rockies trough, moderate rain from elevated
convection will remain possible, and at this time the Watch is
set to continue for all counties along and east of a line from
Gainesville to Stephenville to Goldthwaite.

The Flood Watch is set to expire at midnight Wednesday night
after one of the stronger shortwaves lifts northeast of the
region. The cold front will have briefly become stationary over
southeast Texas, but should begin to lift northwest as a stronger
shortwave swings down through the Desert Southwest and a lee-side
surface cyclone develops. So after a lull in precipitation
Wednesday night and Thursday, showers and storms will ramp up
again Thursday night and Friday as strong lift arrives from the
west. The surface boundary will again provide added focus for
development, and some locally heavy rainfall may again be a
possibility. We will likely need to look into the possibility of
another Flood Watch sometime between late Thursday and late
Saturday.

The main trough axis is progged to finally move east across the
Plains over the weekend. Precipitation will come to an end from
west to east late Saturday or Sunday. A few days of dry and
seasonable weather is likely Sunday and Monday, followed by
another system approaching around the middle of next week.


30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    35  36  36  51  47 /  80  90  50  70  80
Waco                42  42  39  52  48 /  90  90  40  60  70
Paris               39  42  42  55  50 /  90  90  70  70  90
Denton              34  35  35  50  44 /  70  80  50  70  80
McKinney            36  36  36  51  47 /  80  90  50  70  80
Dallas              37  37  37  52  48 /  80  90  50  70  80
Terrell             40  40  40  55  49 /  90  90  60  60  80
Corsicana           41  42  41  55  51 /  90 100  60  60  80
Temple              42  44  39  53  49 /  90  90  40  60  70
Mineral Wells       31  33  32  47  40 /  60  80  40  70  60

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Wednesday evening for TXZ092>095-102>107-
116>123-130>135-143>148-157-159>161.

Winter Weather Advisory until 6 PM CST Wednesday for TXZ091-092-
100>102-115>117-129.

&&

$$


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.