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Area forecast discussion 
National Weather Service Fort Worth Texas
1155 am CST Monday Dec 22 2014

Aviation...

For the 18z tafs...timing the wind shift associated with a cold
frontal passage at the start of the forecast period...and timing
the onset of rain tomorrow morning are the primary forecast
challenges.

A cold front was moving across the dfw area between 17 and
18z...so started the tafs off assuming the front had just passed
through most local area airports beginning at 18z. Winds will
initially be west-northwest behind the leading edge of the
front...but should veer to the northwest a couple of hours behind
the front. The strength of the winds while out of the west-
northwest are expected to be weak enough to prevent significant
crosswind issues. 10-15 knots winds are expected during this time.
Winds will likely pick up to 15 kts with some higher gusts once
winds veer to the northwest later this afternoon.

The consensus of 12z model data has caused a significant increase
in the forecast confidence for rain across the dfw area tomorrow
morning. Morning deterministic model runs all show a very strong
band of frontogenetic forcing from 850 to 700 mb sloped over the
dfw area tomorrow morning. Models also show that the atmosphere is
conditionally unstable to sloped vertical motions along this
elevated front...so expect banded light to moderate rain shower
activity to impact the tafs for much of the period between 12 and
18z tomorrow.

Models are cold enough for snow from near the 850 mb level
upwards...so once aircraft climb above the 850 mb level...they
will be doing so through light to moderate snowfall. However...all
model guidance has the atmosphere below the 850 mb level well
above freezing...so all snow is expected to melt before reaching
the ground at this time. Model dew points at the surface are in
the lower 40s...so confidence in all all-liquid forecast is fairly
high. Also...upstream surface observations across the Central
Plains are in the mid-40s...so there's really no reason for
significant cooling in the lower atmosphere over the next 24
hours.

Rainfall is expected to end from northwest to southeast across the
region tomorrow afternoon. Forecast soundings show ceilings holding at
VFR levels at this time...although periods of MVFR ceilings cannot be
ruled out during heavier bands of rainfall.

Cavanaugh



&&




Previous discussion... /issued 330 am CST Monday Dec 22 2014/
when are we gonna see the sun? That has been one of our most asked
questions lately...and I think it will be today. Southwest
downslope flow has already eroded the low clouds as far east as
Fort Worth and all areas should be partly to mostly sunny by middle
afternoon...with only middle-high clouds to partially block the sun.
Winds will veer westward and then northwest today as a cold front
pushes into the area.

Clouds will increase overnight as an upper trough follows the
front. We are expecting a decent coverage of light rain...but
precipitation will be light and quantitative precipitation forecast consequently low. Tuesday morning...a
few models are hinting that it may get cold enough aloft to make a
few flurries in western/northwestern counties. There is quite a
bit of dry air below 5000 feet...and the middle layers are drying as
well so the chance of any flurries seems low. Have not added them
to the weather grids since if they occur they will not accumulate
with temperatures above freezing...but they may provide visual
interest in the aforementioned areas.

Wednesday and Thursday mornings will be cool...with the northwest
two thirds of north/central Texas possibly dropping to or just below
32. Gusty south winds on Thursday plus sun and dry air will
provide a rapid warm up and highs should be in the 60s. The dry
air and gusty winds will elevate fire weather danger
conditions...so outdoor burning should possibly be delayed for
another day.

The Friday cold front will produce highs below normal for
Saturday...and near normal for Sunday/Monday. The European model (ecmwf) does bring
a stronger trough across on Saturday...and if this feature
continues in future runs...precipitation chances will increase. Of
interest in the extended is a cutoff low in the southwest U.S. On
day 10 that could bring multiple chances at precipitation next week. 84




&&



Preliminary point temps/pops...
Dallas-ft. Worth, Texas 64 45 53 36 49 / 5 10 30 5 0
Waco, Texas 68 45 54 36 52 / 5 10 30 5 0
Paris, Texas 61 43 53 35 46 / 10 10 40 10 0
Denton, Texas 63 42 53 35 48 / 5 10 30 5 0
McKinney, Texas 63 43 52 35 48 / 5 10 30 5 0
Dallas, Texas 64 46 53 37 49 / 5 10 30 5 0
Terrell, Texas 64 46 54 36 48 / 5 10 30 5 0
Corsicana, Texas 67 47 54 36 50 / 5 10 30 5 0
Temple, Texas 69 46 54 35 52 / 5 10 30 5 0
Mineral Wells, Texas 64 41 51 33 50 / 5 30 30 0 0

&&

Forward watches/warnings/advisories...
none.

&&

$$

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