FXUS64 KFWD 152118

Area Forecast Discussion
National Weather Service Fort Worth TX
318 PM CST Fri Feb 15 2019

/Through Tonight/

Big temperature changes coming to North and Central Texas tonight.
1800Z surface analysis revealed a 1004 mb surface low over Dallas.
A cold front runs through this surface low out into West Texas,
and to the east into southern Arkansas. This cold front demarcates
the boundary between continental arctic (cA) air to the north and
maritime tropical (mT) air to the southeast of the surface low.
The air mass over East Texas is characterized by temperatures in
the 70s and dewpoints in the 50s, while the air mass to the north
of the cold front over the Sooner State is characterized by
temperatures in the 30s and dewpoints in the 20s.

The cold front has been shy about moving south through the day
with little in the way of upper-level support to encourage it to
continue southward. The southward push should begin forthwith
however as an upper-level shortwave trough along the lee of the
Colorado and New Mexico Rockies ejects into the Great Plains. The
cold front should clear Dallas/Fort Worth in the next few hours,
and reach the Killeen/Temple/Waco area a little after sundown.

Cold air advection behind the front will result in rapidly
falling temperatures, with lows tonight expected to drop into the
30s for the northern two-thirds of our forecast area, and into
the 40s in our two southeasternmost tiers of counties. A light
freeze is expected in rural areas north of Interstate 20 (the
urban heat island effect should keep overnight lows in the
Dallas/Fort Worth Metropolitan Area just above the freezing mark).
While winds will not be particularly strong overnight, northerly
winds at around 10 MPH will result in wind chills in the 20s for
most areas north of Interstate 20 (including in Dallas and Tarrant
Counties). In terms of precipitation potential, the 1200Z RAOB
from Fort Worth showed very dry air immediately above the boundary
layer ahead of the cold front, with both mid-level and low-level
mean relative humidity values below 35%. This lack of moisture
should keep precipitation chances near zero through the overnight



/Saturday through Next Week/

Main focus of the long-term forecast is the return to a
southwesterly mid/upper flow regime through most, if not all, of
next week, and a resultant increase in precipitation chances
(primarily on Tuesday). Right now, we are not anticipating any
significant winter-weather impacts across our area, but surface
temperatures will be close to freezing across western North Texas
so this area will likely be the largest focus going forward. More
info below.

In the meantime, Saturday presents another tricky temperature
forecast, with a large gradient possible across North and Central
Texas. Low clouds, in association with the frontal surface aloft,
are forecast across much of the region during the morning hours.
Through the day, though, strengthening west/southwesterly flow
aloft and increased low-level mixing will advance east across the
region. Cloud cover is expected to gradually diminish from west
to east through the day, but broken/overcast skies will likely
hold steady east of I-35 and north of I-20 into the
afternoon/evening. Therefore, forecasting a tight gradient in
high temps (mid 70s southwest, near 50 northeast) and these cooler
conditions may not be cold enough. Later updates may have to
tweak highs downward for locales in the direction of
Sherman/Bonham/Paris/Sulphur Springs. Additionally, some patchy
drizzle will be possible across East Texas during the day, under
the influence of poleward 925mb theta-e advection.

A passing front brings a low chance for light showers across East
Texas Saturday night. Then temperatures cool on a broader scale Sunday
and especially Monday, as high pressure builds over the
central/southern Plains in response to building heights aloft
behind a Missouri Valley system. Conditions should be relatively
dry, although strengthening southwesterly mid/upper flow will
likely yield a solid plume of upper-level cloud cover across Texas
into early next week. Meanwhile, in the western-US pattern that can`t
stop (won`t stop), another strong jet streak will drop south
along the Pacific Coast Monday, amplifying an already well-
established trough over the Inter-Mountain West.

Ahead of this trough, isentropic ascent atop a shallow, cold air
mass will stream low-level clouds northward Monday night.
Precipitation chances will increase accordingly and should be
light initially. Towards Breckenridge/Graham/Bowie, surface
temperatures may be close to freezing initially, although guidance
continues to suggest any potential for more significant issues
will be just northwest of our area. Still, given the proximity of
sub-freezing temps and also potential for wet-bulb cooling, have
advertised a slight chance of freezing rain across the far
west/northwest Tuesday morning. With only marginal surface
temperatures, though, believe the potential for significant
impacts is low at this time.

Expect a cold rain everywhere else on Tuesday, as temperatures
range from the mid 30s to upper 40s. The amount of precipitation
over Central and North Texas will likely be a function of the
amplification of an ejecting mid/upper system over the Plains (related
to the jet streak discussed above), given its impact on low/mid-
level thermal advection and frontogenetic ascent. The 15/12Z ECMWF
cycle suggests a more amplified solution, but this potential
remains uncertain. Regardless, a developing cyclone ejects
northeast across the lower Mississippi Valley Tuesday night, which
should bring drying mid levels and an end to any deeper
precipitation processes. There could be a quick mix of light
rain/snow (once again across far northwestern areas) before
precipitation ends Tuesday night, in tandem with a cooling column
behind the aforementioned departing low. Still, not anticipating
any notable impacts at this time due to precipitation ceasing
before surface temperatures cool dramatically.

The region remains under the influence of southwesterly flow aloft
and a switch to low-level return flow by late week. Temperatures
are expected to modify slowly, but precipitation
timing/distribution remains of low predictability, due to the
subtle nature of shortwave troughs within the broader synoptic
regime. In turn, only show slight rain chances by Friday.



.AVIATION... /Issued 1216 PM CST Fri Feb 15 2019/
/18z TAF Cycle/

The main concern continues to be the wind shift expected in the
next couple of hours, as the ongoing stationary front slowly
moves south and out of our area. North winds 10-12 knots will
prevail, but there will be a brief window late afternoon into the
evening where winds could gust up to 17-20 knots. So far, the low
clouds have remained north and east of the DFW Metroplex and Waco
area this morning. Overall, VFR conditions will continue, but
some of the guidances are moving some of the low level clouds
near the DFW Metroplex tomorrow afternoon. Confidence is low at
this time to introduce MVFR cigs, but trends will be monitored
this evening and will make the necessary adjustment to the



Dallas-Ft. Worth    34  57  41  60  34 /   0   0   5   0   5
Waco                39  65  45  61  39 /   0   0   5   0  10
Paris               35  50  41  58  33 /   0   0  10   0   5
Denton              31  55  38  57  31 /   0   0   5   0   5
McKinney            33  51  40  58  33 /   0   0   5   0   5
Dallas              36  58  44  60  35 /   0   0   5   0   5
Terrell             37  57  45  60  36 /   0   0  10   0  10
Corsicana           40  61  48  62  39 /   0   0  10   0  10
Temple              42  68  48  64  41 /   0   0   5   0  10
Mineral Wells       32  61  39  60  31 /   0   0   5   0   5





NWS FWD Office Area Forecast Discussion