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

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FXUS64 KFWD 220519
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1119 PM CST Wed Feb 21 2018


.AVIATION...
/06z TAFs/

No major changes to previous TAFs other than to include a brief
TSRA mention for DFW Metroplex airports around midday Thursday.

IFR/LIFR cigs currently overspread all of North and Central Texas
in wake of today`s rainfall. These conditions will prevail
overnight with occasional mist/drizzle which will reduce
visibility into the 1-3SM range. Temperatures at TAF sites will
hold predominantly in the mid 30s into Thursday morning while this
mist and drizzle is occurring.

By 15z, an increase in convection can be expected to the south and
west of the TAF sites. These showers and isolated storms are
expected to move northeastward and affect airports through much
of the day Thursday while predominantly IFR conditions persist.
Have only included 2 hours of thunder right around midday,
although this may need to be extended in subsequent TAFs. There
should be plenty of elevated instability available to support
thunder with more robust convection. Lingering showers should be
shifting east of the TAF sites by Thursday evening and some
improvement to MVFR could occur sometime between 00-06z. Another
wave of convection is expected to move through North and Central
Texas beginning sometime Friday morning, but confidence in this
timing remains low. Otherwise, NNW winds around 8-12 kts will
prevail through the TAF period.

-Stalley

&&

.UPDATE... /Issued 950 PM CST Wed Feb 21 2018/
Today`s batch of rain has nearly exited the forecast area to the
east with only lingering showers across the southeast as of 930pm.
Since the heavy rain has ended (for now), the Flood Watch for the
remainder of the forecast area has been canceled with this
update. In wake of today`s rainfall, widespread low clouds remain
locked in place and areas of drizzle and mist will occur within
the very saturated lowest 1 km of the atmosphere overnight. This
remains concerning for areas west of I-35 where temperatures will
stay below freezing overnight. Additional very light ice
accumulation will be possible where any drizzle occurs, especially
on elevated surfaces.

Towards daybreak, another wave of strong isentropic ascent in the
305K layer should cause numerous showers and a few thunderstorms
to develop across our west/southwest zones. This activity should
stream northeastward and become increasingly widespread through
the morning hours. I`ve added thunder to the forecast during this
time as latest high-res model soundings suggest as much as 500
J/kg of elevated instability could be present. This will also mean
the potential for additional convective freezing rain across
several of our western counties where a Winter Weather Advisory
remains in effect through noon tomorrow. Temperatures will likely
stay below freezing in these locations through the entire morning
and additional ice accumulations of around 1/10th of an inch
could occur. This would be most likely anywhere from Comanche to
Stephenville to Jacksboro and points north and west. Elsewhere,
temperatures will be in the mid 30s to low 40s as rain and
thunderstorms move in from the west/southwest. Have increased PoPs
slightly for most of the forecast area given the more aggressive
recent solutions depicted by the 3km NAM and HRRR, both of which
have been fairly reliable through the course of this event. If any
of this rainfall becomes heavy or begins training, localized
flooding will be possible in addition to supplemental river rises
due to saturated soils and increased runoff. Otherwise, have
decreased high temperatures tomorrow for most of the area as
widespread precipitation and overcast skies should limit any
heating. However, all areas are expected to climb above freezing
by tomorrow afternoon at the latest.

Products for this update have already been transmitted.

-Stalley

&&

.SHORT TERM... /Issued 404 PM CST Wed Feb 21 2018/
/Through Tonight/

Area radar imagery shows the back edge of heavier precipitation
almost to the I-35 corridor this afternoon. A steady eastward
progression is expected to continue as the main forcing for ascent
continues to pull away to the northeast. Temperatures have
remained at or below freezing for much of the day generally north
and west of the Metroplex, where significant amounts of freezing
rain and sleet occurred. Over the last 1-2 hours though, these
areas have warmed to 30-32 degrees.

For the remainder of tonight, precipitation will end from west to
east this evening with the threat for heavy rainfall also
diminishing. Temperatures east of I-35 have remained in the mid to
upper 30s and lower 40s, so no wintry precipitation is expected
through the evening.

Later tonight, most likely after midnight, as a strong shortwave
digs across Arizona and New Mexico, low level flow above the
frontal inversion will begin to strengthen. With ample moisture in
place and with a strong wave of ascent in the 290-300K layer
expected to overspread North Texas, some light drizzle is expected
to develop prior to sunrise. With temperatures below freezing out
west, this drizzle may continue to cause problems with a light
coating of ice expected. As the stronger forcing for ascent
arrives shortly after sunrise, scattered showers and perhaps some
embedded thunder will develop through the morning into the
afternoon. Some of this heavier activity could occur while
temperatures are below freezing mainly north and west of the
Metroplex. For that reason, we`ll keep a Winter Weather Advisory
in effect overnight into midday Thursday. We cancelled the Ice
Storm Warning as the threat for more significant icing has
diminished. It should be stressed that dangerous travel conditions
are likely to persist out west through the overnight hours.

Concerning the flooding threat...Heavy rainfall is expected to be
confined to mainly this evening across the eastern half of the
region. We continued the Flood Watch until midnight mainly from
Dallas northeast where the heavier rains have already occurred.

Dunn

&&

.LONG TERM... /Issued 404 PM CST Wed Feb 21 2018/
The wet pattern will continue from Thursday through the day on
Saturday and then we will finally have a dry forecast from
Saturday evening through Monday night before our next rain chances
on Tuesday and Wednesday.

Thursday...light freezing rain chances will continue for western
and northern counties that are in the winter weather advisory
through the morning hours before temperatures rise above freezing
by the afternoon. Elsewhere rain chances will increase throughout
the day as moisture streams into north TX from southwest to
northeast. While rain is a good bet in most areas the good news is
that we are not expecting large rainfall amounts like we have
seen the past few days. The heaviest rainfall amounts will likely
be for areas east of I-35E as models are showing PWATs of 1.4+
inches.

Friday and Saturday...Rain chances continue into Friday and
Saturday as southwest flow aloft will persist due to a pesky slow
moving large scale upper level trough to our west. By Saturday
morning, the base of the upper trough will approach the Texas
Panhandle and a surface low is progged to set up on the leeside
of the Rockies in western KS. The GFS is showing a fairly intense
surface low with a front trailing southward into north TX and
hinting at a linear system evolving along the frontal boundary as
it moves from west to east throughout the day on Saturday. There
could even be some severe storms as current model timing is
showing good low level convergence setting up by mid-day.
Instability is fairly limited though, particular for our western
zones, but model soundings are depicting a few hours of possible
CAPE to work with for the central and eastern portions of our CWA.
Regardless of whether there will be any severe storm potential or
not we will see a good chance of showers and thunderstorms moving
from west to east throughout the day on Saturday with clearing by
Saturday afternoon for areas to the west and by the evening for
all areas.

Sunday and Monday...Finally a dry forecast! High pressure will
dominate and we will see mostly clear skies and temps slightly
above normal.

Tuesday and Wednesday...Rain returns to the forecast as the High
breaks down and slides eastward and a sfc low and upper level
trough approach from the west.

HOETH

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    35  43  43  57  53 / 100  80  50  80  60
Waco                36  46  45  63  57 / 100  80  70  70  50
Paris               38  48  47  59  56 / 100  90  80  90  60
Denton              32  40  39  54  51 / 100  80  40  80  70
McKinney            35  43  43  57  53 / 100  90  50  80  70
Dallas              36  44  44  58  54 / 100  90  60  80  60
Terrell             38  50  46  62  57 / 100  80  70  80  50
Corsicana           38  49  47  65  59 / 100  70  80  70  50
Temple              38  45  45  66  57 / 100  70  70  60  40
Mineral Wells       28  41  37  53  49 /  20  90  40  80  70

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until noon CST Thursday for TXZ091>094-
100>103-115>117-129>132-141.

&&

$$

26/14



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