Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Fort Worth Texas
642 PM CST Wednesday Dec 4 2013
Concerns...frontal passage timing...ceilings...onset of freezing precipitation.
The initial frontal boundary has been slow to progress southward...
and at nightfall...it remains draped across the Dallas/Fort Worth
metroplex. The Arctic air is still in Oklahoma...but pressure rises
there suggest the air mass will deepen and begin surging southward
this evening. Metroplex tafs begin with north winds...speeds
increasing after midnight when the Arctic air arrives.
Perfect forecast guidance suggest some MVFR ceilings will be possible
overnight near the top of the Post-frontal layer. MOS is less
impressed...and with the stratus upstream confined to northeast
Oklahoma...will forgo including any at this time. Will begin MVFR
ceilings with light rain mid-morning...but significant precipitation
will likely wait until Thursday evening. Have introduced the onset
of freezing rain middle-evening Thursday within the extended portion
of the dfw taf. Since the freezing line may reach the metroplex
earlier than the current forecast...aviation interests should
continue to monitor updates about this developing winter weather
south flow may prevail at Waco until after midnight. Onset of
light precipitation in central Texas will likely be later than at
metroplex sites...potentially middle-afternoon Thursday. At this
time...temperatures are expected to stay above freezing at Waco
until around daybreak Friday morning...when the rain may
transition to freezing rain...but this too is subject to change.
Previous discussion... /issued 321 PM CST Wednesday Dec 4 2013/
We/ve upgraded and expanded the Winter Storm Watch to a Winter
Storm Warning northwest of a Goldthwaite to Canton line and added
a Winter Weather Advisory southeastward to a Temple to Palestine
Today/S front has reached a north of Paris to Eastland line by 2
PM and will continue to move south overnight. Much colder air is
spreading through Oklahoma and will invade North Texas later tonight
and central Texas Thursday morning and early afternoon. Light rain
should begin overnight due to frontal lifting and isentropic
Thursday through Friday...temperatures will not change very much on
Thursday due to cold air advection...clouds and precipitation.
Some freezing rain will be possible over the far northwest
counties before sunset. Conditions will continue to deteriorate as
freezing rain becomes more predominate as the cold air deepens.
Moderate to heavy rainfall and freezing rain is possible Thursday
middle evening through early Friday morning generally northwest of a
Hamilton to Dallas to Paris line with the axis aligned from
Comanche to Sherman. Isolated thunder may also occur after
midnight. If this rainfall materializes...then a significant ice
storm could develop if temperatures can fall into the 20s.
However...this could also be a case where rain falling through the
warm nose aloft gains enough heat to prevent surface temperatures
from falling much below freezing. Thus...the temporal and spatial
characteristics of the transition to all freezing rain remains
hard to determine. It could remain west of the metroplex through
Friday midday or it could migrate east across the metroplex before
daybreak and during the morning hours. By any token...temperatures
above house tops will be cold enough for ice to accumulate on
elevated surfaces and structures...and this could bring down power
lines and tree limbs...and make bridges and overpasses icy.
As the freezing air continues to deepen on Friday...sleet will
become more likely...especially over the northern half of the County Warning Area.
Sleet amounts could total up to one half inch. The wintry
precipitation should end for Friday night...but it will return
Saturday through Sunday as an upper disturbance moves across the
With cold temperatures remaining across the region through much of
this forecast...ice accumulations will likely hang around through
the weekend and in some areas through Tuesday.
Once the Arctic air settles over the region...highs are not
expected to warm above 40 degrees until the middle of next week.
Lows will vary day to day...but will likely will be in the teens
and 20s this weekend through Tuesday morning. Some Red River
locations may see single digits on Tuesday morning. 75
Preliminary point temps/pops...
Dallas-ft. Worth, Texas 38 38 26 29 19 / 20 50 90 50 10
Waco, Texas 50 50 29 32 21 / 20 40 80 50 10
Paris, Texas 39 39 27 29 17 / 20 50 90 60 10
Denton, Texas 34 37 24 26 17 / 20 60 90 50 10
McKinney, Texas 38 38 25 27 18 / 20 50 90 50 10
Dallas, Texas 38 38 26 29 20 / 20 50 90 50 10
Terrell, Texas 42 42 27 29 20 / 20 40 90 50 10
Corsicana, Texas 50 50 29 33 22 / 20 40 80 60 10
Temple, Texas 56 56 30 32 22 / 20 40 60 60 10
Mineral Wells, Texas 33 36 23 25 17 / 20 60 90 40 10
Winter Storm Warning from 6 PM Thursday to 6 PM CST Friday for
Winter Weather Advisory from 6 am to 6 PM CST Friday for txz135-
Winter Storm Warning from noon Thursday to 6 PM CST Friday for