Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Fort Worth Texas
325 PM CDT Wednesday Apr 23 2014

an approaching shortwave is still in The Four Corners area at this
time...but ascent is occurring well in advance of this feature. A
tropical plume of moisture has been streaming into West Texas...
with persistent middle clouds...and high-based showers/storms have
been ongoing since the morning hours in eastern portions of the
Texas Panhandle. Lee surface troughing below has quickly
intensified the low-level moisture gradient...and this dryline
will be the focus for more widespread convective initiation later
this afternoon as the middle-level clouds move away from the unstable
area to the east of the boundary. Our area of interest for
initiation will be generally from Vernon to Abilene...where
temperatures are already in the middle 80s with dew points near
60f...which equates to MLCAPE values near or in excess of
2000j/kg. A cumulus field continues to increase in this area...but
only minimal vertical extent is evident at this time. Expect
initiation in western portions of North Texas will begin between 4
and 6 PM CDT.

Individual cells will move quickly northeast...but the activity
will have a tendency to gradually propagate to the east...invading
the forward County Warning Area this evening. With deep layer shear exceeding 40kts
and steep middle-level lapse rates...updrafts rooted in a very
unstable boundary layer will be able to quickly produce large
hail. Local values will likely be too high for a significant tornado
threat. As the storms move into North Texas...they will encounter
a stabilizing boundary layer and generally increasing cap
strength (and decreasing helicity). The result will be either:
(1) steadily dissipating storms... or (2) storms that gradually
separate from the boundary layer. The latter does not necessarily
imply a significant decrease in intensity...with steep lapse rates
aloft maintaining the potential for hail. The bulk of any
remaining activity will likely be along and north of the I-20
corridor late tonight.

The shortwave trough axis will pass through the area Thursday
with associated frontal passage. Shower/storm chances will shift
east of the I-35 corridor...the back edge generally coincident
with the two aforementioned features. The shortwave will be
potent...but it appears the main forcing for ascent be north of
the Red River. There will remain the potential for small hail in
eastern zones midday into Thursday afternoon...but the severe
threat appears low.

Southerly flow will quickly return Friday as a dryline quickly
develops across West Texas. This will bear watching for
development...but any storms should dissipate long before they
could reach North Texas. Another potential area of interest will
be the retreating 850mb front...which will be draped west-to-east
across central Texas...above a significant moisture discontinuity
at the surface. With minimal convergence along the boundaries and
no upper support...did not introduce any probability of precipitation/weather at this time.

A far more potent system will swing through the intermountain west
on Saturday. A dryline will set up across West Texas once again.
The area and timing of convective initiation may be similar to
today (wednesday)...with any potential activity invading North
Texas during the evening hours. The storm Mode will favor discrete
(potentially tornadic) supercells...but the storm motion may keep
the bulk of the activity within Oklahoma Saturday night. But with
a vigorous low level jet...the activity may have a tendency to turn right
toward North Texas. The low level jet will also serve to maintain a tornado
threat into the evening hours. A transition to an mesoscale convective system with an
enhanced wind threat may occur after midnight.

The extent of precipitation that lingers Sunday morning will have
a considerable bearing on the extent of any additional severe
weather Sunday. A powerful middle-level jet swinging around the base
of the main upper trough will force the dryline eastward...perhaps
as far east as the I-35 corridor by midday. Additional development
of thunderstorms could occur along the I-35 corridor Sunday
morning but would more likely occur in eastern zones during the
afternoon. The boundary may hang up...maintaining the potential
for strong/severe storms throughout the evening hours Sunday.

The associated front will blow through North Texas on Monday.
Reinforcing shots of cool air will follow next week as the upper
low lingers in the eastern Continental U.S.. this will mean little chance for
additional rainfall and persistent below normal temperatures.



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 87 67 82 61 85 / 0 30 20 0 0
Waco, Texas 86 66 83 60 85 / 0 20 20 5 0
Paris, Texas 82 63 78 55 82 / 0 20 30 5 5
Denton, Texas 86 67 82 55 84 / 0 30 20 0 0
McKinney, Texas 85 66 81 52 84 / 0 20 20 0 0
Dallas, Texas 87 67 82 63 84 / 0 20 20 0 0
Terrell, Texas 85 65 81 58 84 / 0 20 20 5 0
Corsicana, Texas 85 65 82 62 84 / 0 20 20 5 0
Temple, Texas 85 65 83 61 85 / 0 20 20 5 0
Mineral Wells, Texas 87 64 83 55 87 / 0 30 10 0 0


Forward watches/warnings/advisories...