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Area forecast discussion
National Weather Service Fort Worth Texas
535 PM CST Wed Dec 13 2017

a cold front has entered North Texas and will move through the
dfw metroplex in the next 3-6 hours. This will cause winds to veer
to the west and eventually to the north by midnight. This front
is slow-moving and likely won't pass through the Waco taf site
until close to daybreak Thursday. Behind the front, winds will
increase across the entire area to 10-15 kts and persist through
Thursday. Otherwise, VFR conditions will prevail with a slight
increase in high cirrus.



Short term... /issued 404 PM CST Wed Dec 13 2017/

The primary weather concern this evening will be the timing of a
cold front which was approaching the Red River at 3 PM. Based on
the current trend in observations, and a blend of the short-term
guidance, we'll bring the front through the dfw metroplex in the 8
to 10 PM time frame, reaching a Palestine to Temple line by 6 am
Thursday. Initially, the pressure rises in the wake of the front
won't be all that great, and thus the northwest winds won't be
that strong through most of the night. May see the speeds pick up
toward morning, however, as high pressure belatedly builds into
the region.

With clear skies and decent cold air advection occurring behind
the front, we'll see overnight lows drop into the 30s just about
everywhere (outside the normal urban heat island areas), with near
freezing readings possible across the far west and northwest



Long term... /issued 404 PM CST Wed Dec 13 2017/
north winds will pour into the region on Thursday, keeping afternoon
high temperatures 15 to 20 degrees cooler than wednesday's in many
areas. Despite the dry postfrontal air currently upstream, without
the deep mixing and downslope flow, thursday's dew points and
minimum relative humidity values will be higher than wednesday's.
Near normal afternoon temperatures should preclude significant
fire weather concerns, but dormant, drought-stressed vegetation
will remain conducive to fire initiation. The breezy daytime winds
could spread such fires and make them difficult to maintain.

Low temperatures will be in the 30s Thursday night. Mostly clear
skies across northern and western zones will allow a few locations
to dip below freezing Friday morning. Aloft, a potent trough will
approach from the northwest. Previous discussions have made
comparisons to the minor sleet event on December 6. The mid-level
moisture still appears less than what was available during that
event, but there are significant differences among the guidance
moisture profiles' evolution. Similar events have proven that this
magnitude of lift can overcome insufficient moisture, and while
we'll maintain a dry forecast, this will need to be continually
monitored as the event approaches.

A reinforcing shot of cool air on Friday will delay the warming
trend until Saturday, but even then, temperatures may only return to
normal. The wild card will be the extent of the westerly component
in the surface wind, which could enhance the daytime temperatures,
particularly across our western zones. However, cloud cover may work
against this process. As an upper low digs deep into Mexico, nearly
pinching off near the sinaloa coast on Friday, the downstream
flow above Texas will back, and cirrus within the subtropical jet
will spill north on Saturday. The extent and density of these
clouds may have a considerable impact on saturday's high
temperatures and the potential for fire weather concerns.

This plume of moisture will allow the atmosphere to gradually
moisten from the top down, a process that will initially be the most
effective in our southern zones. Rain chances will spread across all
of North Texas Saturday night. As an impulse embedded in
southwesterly flow exits to the east on Sunday, the rain chances
will end from west to east. With marginal instability throughout the
event, showers will likely dominate with the best potential for
embedded thunderstorms across central and East Texas. Significant
drought relief is not anticipated, but precipitation totals this
weekend may be 1/4" to 1/2" across our eastern zones.

Guidance quickly diverges with the upper pattern early next week,
reducing confidence in any additional precipitation beyond the
weekend system. The forecast for the upcoming workweek will be dry
with temperatures steadily climbing above normal.



Preliminary point temps/pops...
Dallas-ft. Worth 40 57 36 56 37 / 0 0 0 0 0
Waco 37 61 37 57 34 / 0 0 0 0 0
Paris 37 53 33 54 33 / 0 0 0 0 0
Denton 35 56 32 56 34 / 0 0 0 0 0
McKinney 34 55 33 55 34 / 0 0 0 0 0
Dallas 41 58 37 56 37 / 0 0 0 0 0
Terrell 36 58 33 56 33 / 0 0 0 0 0
Corsicana 38 60 35 56 35 / 0 0 0 0 0
Temple 37 61 37 58 35 / 0 0 5 0 0
Mineral Wells 35 57 31 55 31 / 0 0 0 0 0


Forward watches/warnings/advisories...

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