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Area forecast discussion 
National Weather Service Fort Worth Texas
645 PM CDT Friday Jul 3 2015

late afternoon convection has diminished considerably over North
Texas over the last hour as weak boundary appears to have become
quite a bit more diffuse. There also appears to be at least some
weak subsidence in place as any activity that does try to develop
quickly diminishes. In the immediate short term...have lowered
probability of precipitation to 20-30 percent through the remainder of the evening but
will continue to monitor upstream activity. There is another
shortwave moving through the Central Plains that will provide
ascent overnight to our north. Any shower and thunderstorm
activity that can get organized to our north may push into North
Texas later tonight. Other than some minor adjustments to probability of precipitation
through the next 6 major changes made at this time.



/issued 639 PM CDT Friday Jul 3 2015/
the trend during the afternoon has been for the thunderstorms
across southern Oklahoma to weaken as they moved southeast into
North Texas. Expect this trend to continue this evening. The
showers that formed farther south...closer to the I-20 corridor...
have been short-lived. Besides some scattered storms along the Red
River...expect only isolated showers/thunderstorms this evening.

There will be a slight chance of thunderstorms overnight through
Saturday along and north of the I-20 corridor...but the chances
are too low to mention in the metroplex taf sites. MVFR ceilings
are expected to develop across south central Texas by 06z...and
spread into the Waco area by 10z. Expect these low clouds to
scatter out by 16z with VFR conditions expected thereafter. South
winds around 10 knots will prevail during the 36 hours.



Previous discussion... /issued 320 PM CDT Friday Jul 3 2015/

From the early afternoon forecast discussion...the primary short
term forecast concern continues to center on the chances for new
thunderstorms developing along a weak frontal boundary located
just south of the Red River. 2 PM surface observations indicated
that the weak front was in place roughly along a Bowie to McKinney
to Emory line. The front has reoriented itself from east to west
earlier this morning to northwest to southeast this afternoon.
Water vapor satellite imagery continues to track one weak
shortwave moving away from the Southern Plains...with a second...
slightly stronger...shortwave trough moving south-southeast over
western Nebraska.

Through this evening...neither of these troughs is in a position
to spread lift across North think that the weak frontal
boundary will continue to be the source of any new rain shower or
thunderstorm development. Think that the coverage of storms near
this boundary will remain scattered in do not think
any evening Independence day related festivities will be a
complete wash out. Delays will be possible...and most likely near
the frontal boundary. At this time the frontal boundary has not
really made any progress due south towards downtown Dallas or Fort rain chances this evening were held in the 20 to 30
percent range. Kept probability of precipitation in the 50 to 60 percent range close to
the frontal boundary.

Any storms that develop through this evening will be capable of
producing cloud to ground lightning strikes...locally heavy
rainfall...and locally strong wind gusts. While severe weather is
not expected for most is difficult to rule out a
damaging microburst from a few storms through this evening.
Locally calculated parameters indicate that cape is on the order
of 1500 to 2000 j/kg...with deep layer shear of 15 to 20 kts.
Regional morning radiosonde observation analysis indicated that middle-level lapse
rates were somewhat meager...and the kfws radiosonde observation had a precipitable
water of 1.90 inches. These parameters support primarily a single
to multi-cell storm Mode capable of producing the threats
mentioned above. Widespread severe weather is not a threat at
this time. Flooding is expected to remain localized...but could
become a larger scale threat if the coverage of storms is greater
than anticipated. The weak forcing along the front suggests that
the coverage will remain scattered to isolated in
nature...limiting the potential for widespread heavy rain and

Overnight into tomorrow morning...the western Nebraska shortwave
trough is expected to continue to move south-southeast overnight
before swinging east tomorrow morning. This trough will spread
some decent lift across the Southern Plains tonight...and will
help increase deep layer shear a bit as well. As a result...think
that the 12z NAM solution for thunderstorm chances has a good
chance of verifying. This solution indicates that a multi-cellular
cluster will develop across eastern Oklahoma after midnight
tonight and move due south towards North Texas.

Our low-level winds are expected to veer strongly out ahead of
this cluster...and pick up in intensity to 20 to 25 kts. While
this is not a super strong low-level jet by any means...the change
in direction and speed in the lower troposphere does promote a
situation where the propagation of new storm development will be
just as strong if not a bit stronger than the mean layer or
advective winds. As a result...the multicell cluster is expected
to sink almost due south...while slowly building or generating new
updrafts on the western flank of these storms dragging the cluster
south-southwest over our northeastern County Warning Area after 09z. Have 60
percent probability of precipitation for areas along and northeast of a Gainesville to
Emory line late tonight through tomorrow morning to account for
this anticipated storm motion.

Think that the backbuilding component of the multicell cluster
will weaken after a few hours of heating helps to mix out the
higher momentum air within the low-level jet. With the shortwave
trough then moving east of the region...the combination of
subsidence behind the trough...and the low-level jet weakening
should cause the entire complex of storms to dissipate just
east/northeast of Dallas by 15z/10am.

For tomorrow afternoon and evening...without any obvious upstream
shortwave trough...thunderstorm chances are expected to remain
tied to whatever convective outflow boundary remains in tact. Left
probability of precipitation in the northeastern County Warning Area as the overnight multi-cell cluster
of storms is expected to dissipate the northeast of the
dfw area tomorrow morning. If the cluster does not pan out as
expected...probability of precipitation may be able to be removed from the forecast
tomorrow. If the cluster moves farther southwest than
expected...will probably need to add at least a small chance of
probability of precipitation to wherever the outflow boundary GOES tomorrow. Most of the
operational model guidance favors a solution that is similar to
the think that most of the area will remain dry for
evening Independence day festivities tomorrow.

Sunday and Monday...upper level shortwave ridging is expected to
build east over the County Warning kept most areas dry with highs in
the lower to middle 90s at this time. Any outflow boundaries that
remain in place or move into the County Warning Area from the north or west may
become a focus for storms. At this time only left some low probability of precipitation in
the forecast for locations along and northeast of a Sherman to
Emory line on Sunday as this is the most likely area where a weak
outflow boundary may remain in place.

Tuesday and Wednesday...medium range guidance is fairly consistent
in indicating that a strong shortwave trough over the Canadian
Pacific coast will move southeast over the northern plains Monday
through Monday night. This will send a cold front south across the
central and Southern Plains Monday night into Tuesday. Models are
fairly aggressive with convection along this front as it moves
southeast towards North Texas. However...this front will be
getting farther and farther away from upper level support on it may stall out before it ever reaches the County Warning Area.

Think that the aggressive convection in model guidance is helping
the front to move southeast into North Texas for Tuesday and
Wednesday. This stalled out frontal boundary across the area
explains why most guidance is advertising 40 to 60 probability of precipitation across a
large portion of North Texas. Kept some precipitation chances in
the forecast during this period...but undercut guidance because
confidence in the front making it all the way into the County Warning Area is low
at this time. It is fairly uncommon for a synoptic cold front to
make it all the way into North Texas in will hedge
towards lower rain chances at this time. If the front is lined up
with storms as it moves does have a chance to make it
into the County Warning Area as advertised. Would like to see a solid line of
storms on that front before bringing it into North Texas however.
If it gets here...will definitely need to increase precipitation
chances during the period.

Thursday through next weekend...most model guidance suggests that
upper level ridging will build over North Texas. If we have 4-5
days of upper level ridging from the end of next week through next
weekend...we may start flirting with 100 degree highs across
portions of north and central Texas. Kept highs in the upper 90s
for now...but this is a large scale pattern that typically
increases the heat this time of year.



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 76 95 76 92 77 / 30 20 10 5 5
Waco, Texas 74 93 74 91 75 / 20 20 10 5 5
Paris, Texas 72 88 73 88 74 / 60 40 20 30 10
Denton, Texas 73 95 74 91 75 / 30 20 10 10 5
McKinney, Texas 74 89 75 90 75 / 40 30 20 10 5
Dallas, Texas 77 95 77 93 77 / 30 20 10 5 5
Terrell, Texas 74 89 74 89 74 / 30 30 20 10 5
Corsicana, Texas 74 91 75 91 75 / 20 20 10 5 5
Temple, Texas 73 93 73 91 74 / 20 20 10 10 5
Mineral Wells, Texas 73 93 73 92 74 / 20 10 10 5 5


Forward watches/warnings/advisories...



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