Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Fort Worth Texas
304 am CDT Friday may 22 2015

Discussion...

Today...
lightning data and the latest satellite loop indicate a shortwave
currently moving northeast out of New Mexico into northwest
Texas. It looks like the best lift associated with this feature
will reach western counties of North Texas by daybreak...and the
latest radar trends /elevated convection increasing to our west/
seem to support this. The showers and storms which affect the
region today will be associated with isentropic ascent /generated
by the shortwave/ above the cool airmass at the surface. The cool
air extends well south of the region behind the cold front which
pushed through the area on Wednesday.

At this time we are not not expecting severe weather...but a few
storms may produce small hail. Rain rates and precipitation totals
should not get too out of hand today...but there may still be some
localized flooding due to the saturated conditions of area soils.
Most of today/S precipitation will occur along and north of the
Interstate 20 corridor as it shifts east across the region.
Activity will diminish from west to east this evening as the
shortwave accelerates off to the northeast.

Memorial Day weekend...
an unseasonably deep West Coast trough will move east across the
southwest states today and Saturday. Lee rockies surface
cyclogenesis will occur in response to the large scale upper
trough. The resulting surface pressure gradient will draw the
front north across North Texas as a warm front tonight and
Saturday. Abundant moisture south of the boundary will surge north
across the region. Precipitable waters are prognosticated to climb to values just shy
of two inches around the time that strong ascent associated with
the upper trough arrives late Saturday. A slow eastward
progression of the system will likely lead to training
thunderstorms late Saturday through Sunday. At this time...the
highest quantitative precipitation forecast remains north of the I-20 corridor...so we will keep
the Flash Flood Watch in place /roughly from I-20 to the Red
River/ Saturday afternoon through Sunday evening. It is possible
that the watch may eventually be expanded south to include the
rest of the County Warning Area...but we will give it another round of model data
and let later shifts make this decision. Some severe storms will
be possible given the time of year and depth of the upper level
system...mainly during the late afternoon hours Saturday...but the
most recent data is indicative of mainly a heavy rain threat.

Next week...
models are now showing another system traversing the plains Monday
night and Tuesday...so we have included fairly high probability of precipitation for the
first half of next week. This system will be much faster
moving...but with expected recent rainfall over the weekend...it
will not take much to aggravate the flooding problem. We will look
at this system in greater detail once we see how the upcoming
events unfold.

30

&&

Aviation...

The previous thinking remains the same...with the exception of the
introduction of VFR ceilings over the dfw area terminals in the short
term. These ceilings are expected to be short lived...as MVFR filters
back into the area within the next hour or two.

Ajs

../previous aviation discussion/...
/issued 719 PM CDT Thursday may 21 2015/
the main aviation concerns for this forecast period are three-
fold: low ceilings throughout this taf cycle...a chance for showers
on Friday...and a return to southerly flow.

Widespread MVFR ceilings remain in place across much of North
Texas...with the exception of areas along the Red River...who
currently have observation in the VFR category. Regardless...expect MVFR
to prevail for our taf sites this evening. Some guidance hints at
IFR ceilings coming in overnight and climatology reveals this is a
definite possibility...as we will be under weak easterly winds
during the overnight hours. Therefore...have decided to place IFR
ceilings in the dfw area terminals by 09z and for Waco by 04z. Ceilings
should lift back to MVFR by late morning on Friday though.

As far as winds go...weak northeasterly winds are the current
trend...but expect veering to occur overnight and winds to wind
up southeasterly by midday for the dfw area terminals. Waco will
be slower to respond to the approaching shortwave and may not end
up in southeasterly flow until Friday evening.

As hinted at a moment ago...a shortwave will approach the area
over the next 12 hours. This will bring renewed lift for
convection. While the convection...currently in the Texas
Panhandle that developed in response to this upper level
support...will likely stay northwest of the terminals during the
overnight hours...have it mentioned in the tafs during the
morning hours tomorrow. This corresponds to the time when the
upper level support will be strongest over our area. Not expecting
a widespread rain event during this time frame like was observed
this morning...so kept it at vcsh.

In the extended...conditions look favorable for a widespread rain
event to occur this weekend and heavy rain and occasional
lightning will be the primary concerns for the terminals. More
details to come as time progresses.

Ajs



&&

Preliminary point temps/pops...
Dallas-ft. Worth, Texas 75 67 82 68 79 / 30 20 50 70 80
Waco, Texas 77 68 81 69 81 / 30 20 40 60 80
Paris, Texas 72 61 81 68 79 / 30 20 40 70 80
Denton, Texas 73 65 83 68 78 / 40 20 60 80 80
McKinney, Texas 73 65 81 68 78 / 30 20 50 70 80
Dallas, Texas 75 67 83 68 79 / 30 20 40 70 80
Terrell, Texas 76 66 81 70 80 / 30 20 40 60 80
Corsicana, Texas 76 67 82 69 80 / 30 20 40 50 80
Temple, Texas 77 68 80 69 80 / 30 20 40 60 80
Mineral Wells, Texas 74 66 82 67 79 / 50 20 60 90 80

&&

Forward watches/warnings/advisories...
Flash Flood Watch from Saturday afternoon through Sunday evening
for txz091>095-100>107-115>120-129>133.



&&

$$

National Weather Service Glossary of Abbreviations