Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Fort Worth Texas
346 PM CDT Wednesday Oct 1 2014

afternoon satellite imagery shows an extensive cumulus field across the
eastern half of Texas this afternoon indicative of ample low level
moisture being pulled northward ahead of an approaching upper
trough. This shortwave trough can be seen on water vapor imagery
digging into the southwest U.S. And it will continue eastward
overnight. In the immediate short term...our primary concern will
be potential for convective development across the far western
counties this evening. There is a thin band of cumulus that has
developed along a diffuse dryline across west-central Texas.
Temperatures have climbed into the middle and upper 90s across this
region and inhibition is weakening. It is hard to tell whether
there is any additional forcing for ascent being provided to the
area from the approaching trough as Texas currently appears to be
between systems. What is clear though is that forcing will begin
to increase later tonight as the upper trough gets any
activity that does develop might be able to sustain itself for a
while. Went ahead and kept some 20 probability of precipitation across the far western
counties to account for this.

By tomorrow morning the western U.S. Trough will be approaching
the Southern Plains. A surface low will be located across
northwest Oklahoma and will quickly be moving to the northeast
while a cold front begins to surge southward. The guidance has
continued to support a slower arrival of the upper trough but
appears to be consolidated around a midday to middle afternoon
timeframe. This would be favorable for more widespread convection
along the cold front as temperatures are likely to warm into the
middle 90s across parts of North Texas...especially along and east of
I-35. The tricky part for the 8 million or so people who live in
North Texas and desperately want rain is exactly where the
thunderstorms initiate along the cold front. High resolution
guidance is very well clustered with initiation occurring between
3 and 5 PM Thursday afternoon. The variance comes with a couple
of models showing thunderstorms developing from Dallas eastward
and others indicating that they will develop farther west. This
forecast will favor a slightly farther west development based on
the strong forcing coming in along the front during peak heating
which should help weaken the cap quickly. Our current forecast
will indicate thunderstorms developing in the middle afternoon along
a line from near Gainesville southwest to Decatur and Weatherford.
Initial activity will primarily remain north of I-20 but should
quickly expand southward as the front moves east. All of this
means that the western half of the metroplex and areas west of there
could miss out on the more significant rainfall. Areas along and
east of I-35 will have much better chances for rainfall. The front
will continue east through the evening with showers and
thunderstorms affecting primarily the eastern half of the County Warning Area
through midnight before quickly coming to an end with frontal passage.

Concerning severe weather potential...with the upper forcing
coming in coincident with peak area of moderate
instability will have developed along and ahead of the cold front.
Deep layer shear of around 45 kts will be more than sufficient
with instability around 2500 j/kg to support severe convection.
Wind profiles become veered rather early in the event which is typical
of frontal type convection...and this is likely to limit the
overall tornado threat. The exception may be areas south of
Interstate 20 where capping will be a little stronger and a discrete
supercell or two may develop along or ahead of the cold front.
Again...while wind profiles dont appear to be favorable...discrete
supercells can quickly modify the local the potential
needs to be monitored. The most likely severe threat will be large
hail and damaging winds from squall line convection across the
eastern half of the County Warning Area.

Thunderstorms will come to an end Thursday night as the front
clears North Texas. It wont be considerably colder behind the
front but it will be much drier. Dewpoints will fall into the 30s
by late Friday with temperatures in the upper 70s and lower 80s.
The coolest morning will be Saturday when the surface high is
centered across the region. Temperatures will drop into the 40s
and lower 50s with significant topographical effects due to near calm
winds. The forecast will remain dry into next week although
moisture will work back into the area by Monday and temperatures
will warm back into the middle and upper 80s.



/issued 103 PM CDT Wednesday Oct 1 2014/
/18z tafs/

Not a whole lot of change from 12z tafs outside of a few minor
tweaks on stratus timing tonight. VFR with scattered clouds is
expected through bulk of the large-scale forcing
remains well north and west of the airports. Timing of MVFR ceilings
into dfw will occur between 09z-12z...and between 07z- 09z at
Waco. It is possible with the 35-45kt low level jet closer than last night
that stratus may develop sooner with timing bumped up on later
forecasts. For now...continuity was the best path on the stratus
timing. The borderline IFR ceilings at Waco have been removed due to
stronger low level winds just above the surface. This should keep
the bottom of the boundary layer more mixed and ceilings within the
MVFR category through late morning Thursday. South-southeast
winds will remain steady 10-15 kts through sunrise Thursday.

By midday Thursday...winds should veer and strengthen just ahead
of an approaching cold front with sustained speeds increasing to
between 15-25 kts. Storm initiation should occur near or just
northwest of dfw airports late in the afternoon as the cold front
and large-scale ascent arrives with a few possible severe. Have
introduced thunderstorms in the vicinity at dfw later in the afternoon or by 02/22z. A
frontal passage and wind-shift will likely occur by early evening Thursday
at dfw metropolitan airports and by middle-late evening at Waco. Northwest
winds will gradually increase to between 10-15 kts behind the cold
front Thursday night.



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 75 95 61 83 53 / 10 60 20 0 0
Waco, Texas 74 94 58 85 52 / 5 30 40 5 0
Paris, Texas 72 92 57 77 48 / 10 50 60 0 0
Denton, Texas 73 94 57 81 47 / 10 60 10 0 0
McKinney, Texas 73 94 58 80 46 / 10 70 30 0 0
Dallas, Texas 75 95 61 82 54 / 5 60 30 0 0
Terrell, Texas 74 93 60 80 50 / 5 40 50 0 0
Corsicana, Texas 74 93 60 83 52 / 5 30 60 5 0
Temple, Texas 73 92 61 85 52 / 5 20 50 5 0
Mineral Wells, Texas 72 92 56 80 49 / 10 30 5 0 0


Forward watches/warnings/advisories...




National Weather Service Glossary of Abbreviations