Scientific Forecaster Discussion

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Area forecast discussion...updated 
National Weather Service Fort Worth Texas
1131 PM CDT Sat Apr 19 2014

challenges still remain regarding ceilings and if cap can moisten and
lift enough for isolated showers toward sunrise near airports with
approaching and weakening mesoscale convective vortex over west central Texas. This
activity is being driven by shortwaves moving quickly northeast
out of Mexico toward far West Texas. Have very low confidence in
ceilings going below VFR with mixing from approaching lift and nothing
seen upstream near the Gulf. Will hold to VFR and expect most
activity to be either sprinkles or virga by the time it arrives
here toward sunrise. Otherwise...light S/southeast winds 6 kts or less
will increase by late morning to around 10 kts. Did throw in vcsh
in the extended period after 00z Monday as cap continues lifting
weakening and system approaches from the west.



kfws 00z sounding indicates a substantial layer of warm air between
800 and 700 mb. The warm layer also extend much farther southwest
based on how storms are struggling as they move east out of the
Permian Basin. We do expect the cap to weaken overnight and Sunday
due to increasing large scale lift from the ejecting short wave.
It appears that the best rain and storm chances across North
Texas will hold off until Sunday afternoon/Sunday night.

The current forecast is in good shape and no update is needed at
this time.



Previous discussion... /issued 252 PM CDT Sat Apr 19 2014/
broad upper trough...currently located in Baja California region...will
gradually lift east and northeast across the southern rockies and
then across OK/Texas by late Monday. This trough...and associated
smaller-scale impulses...will bring several rounds of convection
to north and central Texas from late tonight through Monday night.

Lead impulse...associated with convection in far West Texas this
afternoon...will weaken as it moves east northeast tonight. Widely
scattered showers and isolated thunderstorms will spread into western
sections of North Texas after midnight...with isolated showers as
far east at the Interstate 35 corridor by sunrise Sunday morning.

For Sunday afternoon and Sunday evening...the coverage of showers
and thunderstorms will increase across the area as the larger
scale upper trough moves into West Texas. Will forecast highest
probability of precipitation across the north and taper probability of precipitation to slight chance category in
the central Texas zones. Mesoscale model output suggests that a
cluster of showers and elevated thunderstorms will move across
western and northern sections of North Texas Sunday afternoon and
Sunday night. This output seems reasonable and appears to be
related to best large scale forcing for ascent seen in 500-300 mb
q-vector convergence forecasts from several operational models. Will
forecast likely probability of precipitation in the region from Graham to Gainesville. A
strong storm with small hail and gusty winds is not out of the
question for Sunday afternoon and Sunday night in these areas.
However...the threat for severe thunderstorms Sunday afternoon and
Sunday night is expected to remain across West Texas where
surface-based storms can develop near the dryline and along the
upper trough axis. These severe...surface-based storms are expected
to weaken drastically as they approach the western County Warning Area late Sunday

The potential for an episode of severe weather is increasing for
parts of north and central Texas on Monday. Subsidence early in
the day should lead to breaks in the cloud cover...allowing
insolation to help push surface based convective available potential energy to over 2000 j/kg
locally. With upper trough in the area and at least moderate
instability...chances for multicell clusters of strong to severe
thunderstorms will increase by afternoon. Will keep probability of precipitation at 40-50
percent over a large part of North Texas on Monday as convective
development focuses along a slowly advancing cold front. The most
likely areas for severe storms will be tied to regions of
strongest instability...the exact timing/location of the upper
trough... and best convergence along the cold front. At this
time...the favored region for severe storms on Monday looks to be
east of Interstate 35 and north of Interstate 20.

Scattered showers and storms will end from northwest to southeast
late Monday night as the cold front moves into south Texas. Large
scale subsidence behind the departing trough should lead to mostly
clear skies and quiet weather Tuesday and Wednesday.

The next chances for showers and thunderstorms will be Wednesday
night into Thursday night. A progressive trough will move into the
intermountain west on Wednesday...then move into the plains on
Thursday. The strongest large scale forcing for ascent looks to
remain well north of will keep probability of precipitation at or below 30
percent at this time. However...prospects for at least moderate
instability and perhaps a dryline in the area could lead to an
episode of severe thunderstorms Thursday afternoon into Thursday

Dry weather and above-normal high temperatures are forecast for
next Friday and Saturday as the trough moves east of the area and
largely zonal flow dominates the central Continental U.S..



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 62 77 63 81 61 / 10 30 40 50 30
Waco, Texas 59 78 61 81 61 / 10 30 20 40 30
Paris, Texas 57 76 60 76 58 / 5 20 40 50 40
Denton, Texas 59 76 62 78 57 / 20 30 50 50 20
McKinney, Texas 57 76 62 77 57 / 10 30 40 50 30
Dallas, Texas 62 78 64 79 61 / 10 30 40 50 30
Terrell, Texas 59 78 61 79 60 / 10 30 40 50 30
Corsicana, Texas 59 78 61 79 61 / 5 20 30 50 30
Temple, Texas 58 76 59 81 61 / 10 30 10 30 30
Mineral Wells, Texas 58 76 60 81 57 / 20 40 40 50 20


Forward watches/warnings/advisories...