Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Fort Worth Texas
235 PM CST Friday Nov 28 2014
south/southwest winds continue to increase over the region today
as surface pressures drop across the Front Range of The Rockies.
A 995mb surface cyclone over eastern Montana will intensify and
head eastward into the Great Lakes...opening the door for an
Arctic airmass to invade the plains over the weekend. After an
unseasonably warm weekend...this cold front will arrive Monday
morning and bring a dramatic cool down to north central Texas.
850mb temperatures will increase to 16c to 18c over the region
tonight...which should allow high temperatures to warm into the middle 70s
over most of the County Warning Area tomorrow. Southwesterly flow above the
surface will keep most of the overnight stratus east of I-35
tonight and Saturday morning. The clouds east of I-35 should mix
out by noon...which means mostly sunny conditions are expected.
Otherwise a breezy...if not windy...day is expected Saturday...but
it appears speeds will be just shy of Wind Advisory criteria. A
subtle backing and weakening of the winds occurs Saturday night
which will allow stratus to encompass most of the area by Sunday
morning. These clouds will be more stubborn to erode...and is the
only reason temperatures will not reach the 80s Sunday afternoon.
Meanwhile the strong cold front will be heading southward through
the plains and should arrive into North Texas early Monday
morning. Forecast high/low temperatures Monday are very sensitive
to the exact timing of the front...and if the front is just a
couple hours faster than expected...they will need to be lowered.
The exact forecast highs/lows are largely frivolous...because
regardless of frontal timing...temperatures will be falling into
30s for the northwest half and into the 40s for the southeast half
of the area by midday Monday. Ahead of the front a shallow layer
of moisture will exist below a Stout thermal inversion. While just
a few low-topped weak showers will be possible ahead of the front
over the east...the rapid cooling of the low level column is
suggestive of widespread drizzle for a few hours behind the front.
It is entirely possible freezing drizzle may occur over the
north/northwest zones before the precipitation ends. Since the ground
will be warm and the drizzle will be very light...will hold off
on mentioning it in the forecast. In addition...there is little to
no threat of significant measurable precipitation behind the front
due to very little moisture above 850mb...no organized lift
aloft...and anemic lapse rates. This raises confidence that no
impacts from any wintry precipitation are expected...and is another
reason to not mention it in the official forecast this far out.
With the Arctic high tracking more east...as opposed to south early
next week...the cold airmass will remain very shallow over Texas.
In all likelihood...low clouds will remain in place near the
strong frontal inversion. Winds will weaken Tuesday and turn
around to the south by Wednesday. These are good indications that
the clouds will hang around Tuesday...even though model guidance
is breaking through the inversion and indicating sunny skies. As a
result...will undercut guidance for highs on Tuesday...and these
may need to be lowered more if confidence in cloudy skies grows.
By Tuesday night and Wednesday...southerly flow in the low levels
is a good bet that clouds will return even if they do scatter out
Tuesday afternoon. Isentropic lift and moisture may be sufficient
for weak showers over the east Wednesday...and covering most of
the area by Wednesday night and Thursday. The forecast highs for
Wednesday may also be too warm given the clouds and potential
for drizzle/fog. The effective warm front should pass through by
Wednesday night with 60s for highs area wide by Thursday.
Additional low chances for showers will exist with the warm front.
All in all...it is shaping up to be a cool...damp and cloudy
string of days...but unfortunately the precipitation that falls
during this period will not amount to much of anything.
/issued 1121 am CST Friday Nov 28 2014/
VFR conditions expected across most of North Texas through the
period although some low clouds may try to make a run at the
airports during the morning hours on Saturday. Currently a tight
pressure gradient across the region will result in gusty south
southwest winds which will continue into Saturday. Some low level
moisture will surge northward tonight although very strong
southwest winds just above the surface should help keep most of
the associated low clouds along and east of Interstate 35 early
Saturday morning. For now will just include a sct012 at the major
airports for Saturday morning...although MVFR ceilings are expected
east of there. Otherwise...south winds will continue through
Saturday afternoon with VFR skies.
Preliminary point temps/pops...
Dallas-ft. Worth, Texas 54 76 63 77 40 / 0 0 5 5 10
Waco, Texas 54 75 63 76 53 / 0 0 5 10 10
Paris, Texas 52 73 61 74 45 / 0 0 5 10 10
Denton, Texas 53 75 61 77 37 / 0 0 5 5 10
McKinney, Texas 53 74 63 76 40 / 0 0 5 5 10
Dallas, Texas 55 75 63 76 41 / 0 0 5 5 10
Terrell, Texas 55 73 63 74 48 / 0 0 5 10 10
Corsicana, Texas 56 75 62 77 55 / 0 0 5 10 10
Temple, Texas 53 76 63 77 56 / 0 0 5 10 10
Mineral Wells, Texas 50 75 57 76 36 / 0 0 5 5 10