Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Fort Worth Texas
618 PM CDT Monday Jul 28 2014
The cold front has moved south of kact with convection occurring to
the east over central East Texas. Although there is a low chance
for convection around kact this evening and again on Tuesday...do not
have high enough confidence to include in the kact taf.
Otherwise...all terminals will remain VFR through the forecast.
Winds will be northerly overnight with speeds dropping to less
than 10 knots. Winds will become more easterly around/after
midday Tuesday generally 10 knots or less. 75
Previous discussion... /issued 342 PM CDT Monday Jul 28 2014/
a weak cold front entered central Texas this afternoon but has
become nearly stationary...despite increasing surface winds behind
the boundary. Thunderstorms have developed along and behind the
surface boundary as meager mechanical forcing above the frontal
slope is helping very unstable air overcome deep subsidence. July
sunshine and strong surface heating north of the boundary has
allowed Post-frontal air to mix with the air above the frontal
inversion...resulting in the unusual situation of surface-based
convection behind a frontal boundary.
With cape values exceeding 2000j/kg where convection is ongoing...
and precipitable water values topping 2 inches...strong updrafts will allow for
significant precipitation loading. The weak shear is resulting in slow-
moving storms capable of very heavy rain...but individual updrafts
will generally be too short-lived for any flooding concerns. Rain-
cooled air and associated cloud cover have begun to narrow dew
point depressions at the surface...but some cells will still be
capable of producing downburst winds in excess of 50 miles per hour...
particularly with collapsing storms.
Although cool/dry advection behind the boundary has so far been
modest...the 60-degree isodrosotherm is expected to slip south of
the Red River tonight. The northern extent of the ongoing
convection...which is now from Sherman/Denison to near Lake
Tawakoni...will drift southwestward as drier air invades from the
northeast. The axis of elevated instability...and the primary
focus for activity tonight...will set up across the southwestern
zones. This convection may persist into the late morning on
Tuesday. An unusual gradient between dry conditions in East Texas
and maritime tropical air in western North Texas will keep the
Tuesday afternoon activity primarily west of I-35.
The first of a pair of shortwaves embedded in northwest flow aloft
will swing into Oklahoma on Wednesday...with its trailing friend
eventually gliding through North Texas on Thursday with an
associated cold front. The best chances for precipitation
throughout the period will be in areas north of the I-20 corridor
and in northeast Texas...but areas farther south could see some
activity Thursday afternoon as the front moves through the region.
Portions of central Texas could reach the century mark Wednesday
if the cloud cover and precipitation fail to make an impact
there...particularly in areas that miss the rainfall Monday and
Tuesday. Thursday temperatures are largely dependent on the
extent of rainfall and lingering cloud cover...but even central
Texas will see milder air arrive on Thursday and Friday.
Middle-Summer cold fronts are always difficult for guidance to
handle...but the upper pattern suggests that the boundary should
be able to clear the County Warning Area...bringing an end to rain chances
Thursday night. However...chose to leave some lingering probability of precipitation in
the southeast on Friday in case the front is not so inclined.
Northwest flow will continue into the upcoming weekend...and north
winds should prevail at the surface. Abundant sunshine will still
allow temperatures to reach the 90s...but the humidity may be a
bit more tolerable than it usually is in early August.
Preliminary point temps/pops...
Dallas-ft. Worth, Texas 74 95 74 95 74 / 30 20 10 20 40
Waco, Texas 74 96 73 98 74 / 40 30 10 10 20
Paris, Texas 69 90 69 81 67 / 20 10 30 50 60
Denton, Texas 71 94 73 94 71 / 30 20 20 30 40
McKinney, Texas 70 92 71 93 72 / 30 20 20 40 50
Dallas, Texas 75 94 75 95 74 / 30 20 10 20 40
Terrell, Texas 71 94 71 94 73 / 30 20 10 30 40
Corsicana, Texas 73 94 72 96 72 / 40 20 10 10 30
Temple, Texas 73 96 72 98 74 / 40 30 20 10 20
Mineral Wells, Texas 70 94 71 97 73 / 30 30 20 20 30