Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Fort Worth Texas
1048 PM CDT Sat Jul 12 2014

Update...
ridging aloft will allow clear skies to persist overnight and
through the day Sunday. Off to our east...the TUTT over Louisiana
evident on water vapor satellite is currently producing some
convection west of New Orleans. This feature will continue moving
west overnight and Sunday...but feel that subsidence from the
ridge will win out...keeping convection predominately south of
North Texas Sunday. Otherwise...it still looks like temperatures
will approach triple digits in many locations Sunday and
Monday...with rain chances expected Tuesday through the end of
next week. The current forecast looks good with no changes
expected at this time.

30



&&



Previous discussion... /issued 331 PM CDT Sat Jul 12 2014/
an upper level ridge has become centered over Oklahoma with much
of North Texas under strong subsidence...experiencing hot and dry
weather. Fortunately dewpoints mixed out well into the 40s and 50s
for many areas this afternoon which has kept heat indices in
check. With low level thickness values continuing to increase
overnight believe several sites will see 100 degrees tomorrow.
Dry weather will be the rule...however water vapor shows a weak
TUTT low is now moving over New Orleans...and this feature will
track westward through south Texas over the next 24 hours. Thus a
stray afternoon shower or storm is possible over the far southeast
zones Sunday but will not mention this in the worded forecast.

Water vapor also shows an unusually strong upper level low now
over Manitoba dropping southeast toward the Great Lakes region as
forecast. Upper level flow over the Central Plains will become
highly amplified which will send a cold front south into Oklahoma
on Monday. Ahead of the front...low level winds will likely
become westerly which will result in further warming across the
northern half of the region. This means Monday afternoon should be
the warmest day for most locations. Isolated convection is
forecast to develop in Oklahoma Monday afternoon and with the flow
becoming more northerly...convection will attempt to drop south
into the northern zones Monday evening. Although the low level
airmass will be dry and stable...the middle levels will feature some
moisture and weak instability for weak elevated convection
generally north of I-20 after midnight. The GFS forecast however
looks over enthusiastic with quantitative precipitation forecast early Tuesday morning and
appears to be displaying the classic symptoms of grid scale
convective feedback. All other guidance paints a drier forecast
and therefore will keep probability of precipitation Tuesday generally at 20 percent for
just isolated activity that may fire up along the front.
Temperatures on Tuesday will be several degrees cooler over the
northern half of the area thanks to weak cold advection and
increased cloud cover. However highs across the southern zones
will remain near normal as the front slows down and loses its push
southward. Prefer the NAM/GFS forecasts which lay the front up
stationary roughly along a Cisco to Palestine line over the
European model (ecmwf)/Canadian forecasts which push it into south central Texas.

The primary challenge in the forecast is the rain potential from
middle to late week. Model guidance continues to indicate that all
of the ingredients for widespread rain...some heavy...are in place
over North Texas. The cold front will be stalled out across The
Heart of the County Warning Area causing precipitable water values to increase
above 2 inches. The airmass will be very moist...uncapped and
contain sufficient instability for convection Wednesday through
Friday. In addition model guidance is in good agreement in showing
two separate shortwave troughs will move through the region in
northwest flow aloft. The first arrives Wednesday with model
guidance consensus targeting the northern half of the County Warning Area and
southern Oklahoma. The second piece of energy moves through on
Thursday evening...taking a slower and more southerly track than
the first. Model guidance is in less agreement with where
convection is favored with the second piece of energy. But because
southerly low level flow becomes stronger and more organized it
likely increases the probability that a mesoscale convective system will develop Thursday
and travel into the warm sector airmass. This means areas south of
the front would get their best chance of rain Thursday and
Thursday night. All in all believe the 12z European model (ecmwf) has the best
looking and most reasonable quantitative precipitation forecast trends through the event. It is
probably too early to start throwing out a quantitative precipitation forecast forecast...but it
seems the northern half of the County Warning Area zones will have higher average
amounts than the south. Temperatures Wednesday and Thursday will
be dependent on cloud cover/rainfall coverage more than any true
cold air behind the front. Sunny areas across the south will
reach the low 90s with ease...but some northern zones may be stuck
in the 70s and 80s. Thursday still looks like the coolest day with
most of the County Warning Area not seeing any 90s for highs.

By Friday the upper trough will begin to move eastward...but will
keep a low chance of convection going due to inherent
uncertainties at this time range. The airmass will continue to dry
out and warm back up to near normal by Saturday with just
isolated afternoon convection Saturday afternoon.

Tr.92

&&




Preliminary point temps/pops...
Dallas-ft. Worth, Texas 76 100 79 101 76 / 0 0 0 5 20
Waco, Texas 71 98 74 98 74 / 0 0 0 0 10
Paris, Texas 73 100 73 98 73 / 0 0 0 10 30
Denton, Texas 71 99 74 100 73 / 0 0 0 10 30
McKinney, Texas 71 99 74 100 73 / 0 0 0 10 30
Dallas, Texas 78 100 80 100 76 / 0 0 0 5 20
Terrell, Texas 74 100 77 100 76 / 0 0 0 5 20
Corsicana, Texas 73 98 74 98 75 / 5 5 0 0 10
Temple, Texas 69 98 72 98 74 / 5 5 0 0 10
Mineral Wells, Texas 68 100 72 100 72 / 0 0 0 5 20

&&

Forward watches/warnings/advisories...
none.

&&

$$

National Weather Service Glossary of Abbreviations