Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Fort Worth Texas
911 PM CST Wednesday Mar 4 2015

Update...
radar presentation depicts the well advertised upper level energy
is now arriving into the western zones. This band of precipitation
will translate across the region during the next few hours and
produce a mix of sleet and snow. Within the last hour across the
area south and west of the dfw metroplex...radar echoes are
increasing and displaying convective characteristics. The 0z forward
sounding showed a few hundred joules of MUCAPE...and forecast
soundings from the RUC/NAM confirm 100-200 j/kg of MUCAPE are
present roughly along and south of I-20. With the increasing
forcing for ascent this convective energy will be tapped...and
expect some locally heavy showers of sleet or snow to develop
across this region. The main time frame for heavy winter precipitation
over the County Warning Area is now through 4 am...with the significant activity
ending from west to east around midnight out west and 4 am in the
east.

The best combination of temperatures cold enough for frozen
precipitation and convective instability is situated along a band
from roughly Comanche to Cleburne to Sulphur Springs. This is
where we believe the band of higher totals of sleet/snow is most
likely with amounts possibly of 2 to 3 inches. Elsewhere generally
a 1 inch amount of sleet/snow mix is expected to the north of this
band...but already a few locations along the Red River have had 1
inch of sleet. Due to the convective instability present with this
system...lots of variation from location to location in snow/sleet
amounts is likely...so dont focus too much on the exact number for
your area.

Essentially no major changes were required to the forecast as it
looks on track. Did update snow/sleet accumulations to focus in
on the aforementioned band where we believe the highest totals
will occur.

Tr.92

&&

Aviation...
/issued 540 PM CST Wednesday Mar 4 2015/
/00z tafs/

Areas of rain...freezing rain and sleet have developed across
North Texas and temperatures continue to fall into the metroplex.
Dfw reported 31 degrees on the last observation which means most
of the precipitation is light freezing rain. No significant
impacts are expected in the immediate short term but conditions
are still expected to deteriorate over the next several hours.
Colder air to the west has allowed a transition over to sleet and
this has begun to accumulate. Think this transition will affect
the metroplex airports over the next couple of hours with
initially a freezing rain/sleet mix then a complete switch to
sleet. Initial look at the 00z sounding from Fort Worth indicated
a warm nose to +7c...which will support mainly rain/freezing rain
until colder air aloft moves in. There is also some elevated
instability which will support convective elements...mainly bursts
of sleet in thunderstorms.

Tafs will feature IFR conditions with -fzra transitioning to sleet
by 02z. There is a period between 04-07z that some thunderstorms
will be possible with bursts of moderate to heavy sleet. Some snow
will be possible by midnight. Once precipitation ends...skies will
be quick to return to VFR.

For Waco...mainly rain is expected with a transition to freezing
rain shortly after midnight then some sleet. Similar to the
metroplex...conditions will rapidly improve after precipitation
ends early Thursday morning.

Dunn



&&




Previous discussion... /issued 325 PM CST Wednesday Mar 4 2015/
the cold front has now cleared our southern counties and freezing
temperatures started moving into our northern and northwestern
counties within the past 2 hours. At 3 PM...the freezing line was
near a line from Sherman to Decatur to Abilene and we are getting
reports of a rain/freezing rain/sleet mix where temperatures are
already at or below freezing. As the freezing line continues to
move southeast this afternoon through the overnight hours...the
transition to a wintry mix will continue to also move southeast.
We expect a few hours of freezing rain will be possible as the
freezing line reaches each location with a transition to mostly
sleet after that. The exception to this will be in the
southeastern counties where it appears temperatures will hold above
freezing until around daybreak tomorrow...so mostly rain is
expected through the night and then some freezing rain may occur
Thursday morning. Back across the northern half of the area...a
changeover to all light snow may occur overnight with some light
accumulations...less than an inch.

The rain and wintry mix will not be constant through the period
with breaks in the precipitation expected. A large break is sort
of developing across the region right now but the next round of
precipitation will occur this evening and overnight. During the
evening and overnight hours...convective pockets of sleet and
possibly freezing rain are likely to occur but will not impact all
areas. Where convective sleet/freezing rain occurs is where we
expect the highest accums of sleet and/or ice...and thus the
highest impacts. Therefore...it is very possible that not everyone
in the warning will meet warning criteria....but due to
uncertainty on where exactly the convection will occur is the main
reason for such a broad warning.

Portions of the Winter Weather Advisory from Lampasas to Waco to
Athens were changed to a Winter Storm Warning this morning...and
accumulations were also adjusted across the region. No additional
changes are being made to the warnings/advisories/accumulations this
afternoon. We expect some of the heaviest accumulations of sleet
to occur along or near a line from Goldthwaite to Ennis to
Cooper. Locations south of this area may be susceptible to more
freezing rain which was the reason for the change to a warning
across part of central Texas. Our northwestern counties are not
expected to receive as much accumulations of sleet and snow as
was forecast 12 hours ago...but impacts...especially to
travel...can still be expected in these counties. With the
precipitation ending from north to south beginning overnight...it
is likely parts of the warning will be cancelled before the noon
expiration time.

In addition to the wintry mix...we also have strong winds to
contend with. The Wind Advisory is now in effect for all areas
through 6 am Thursday morning. Not only will the strong wind
provide a hazardous element against ice coated surfaces such as
power lines...but it will result in low wind chill readings
overnight through Thursday morning in the single digits to lower
20s.

Temperatures on Thursday are expected to warm above freezing as
the sun finally shows in the sky...but stay in the 30s. It is
possible some areas will barely reach freezing where larger
amounts of sleet/ice occur. But based on the forecast of highs in
the 30s and clearing skies...we should see some melting of the
ice tomorrow afternoon. However...any water/ice still on the roads
Thursday night/Friday morning will refreeze as temperatures plummet into
the teens and lower 20s. After that...a gradual warm up is
expected for the next several days.

Much quieter and warmer weather is expected through the end of the
forecast but there is a chance for rain across our southern half
Saturday through Sunday. Have kept probability of precipitation low at 20-30 percent due
to discrepancies between the models.

82/jld




&&



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 25 36 24 42 31 / 100 10 0 0 5
Waco, Texas 29 36 22 44 28 / 100 30 5 0 10
Paris, Texas 24 36 20 40 26 / 100 10 0 0 5
Denton, Texas 22 35 19 43 27 / 100 10 0 0 5
McKinney, Texas 24 36 20 41 26 / 100 10 0 0 5
Dallas, Texas 26 36 25 43 31 / 100 10 0 0 5
Terrell, Texas 26 34 21 42 27 / 100 10 5 0 5
Corsicana, Texas 29 36 25 43 30 / 100 30 5 0 10
Temple, Texas 30 37 23 45 30 / 100 50 5 0 10
Mineral Wells, Texas 24 36 19 44 28 / 100 10 0 0 5

&&

Forward watches/warnings/advisories...
Wind Advisory until 6 am CST Thursday for txz091>095-100>107-
115>123-129>135-141>148-156>162-174-175.

Winter Storm Warning until noon CST Thursday for txz091>095-
100>107-115>123-129>134-141>145.

Winter Weather Advisory from midnight tonight to noon CST
Thursday for txz147-148-160>162-174-175.

Winter Storm Warning from midnight tonight to noon CST Thursday
for txz135-146-156>159.



&&

$$

/

National Weather Service Glossary of Abbreviations