Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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FXUS64 KFWD 190521

Area Forecast Discussion
National Weather Service Fort Worth TX
1121 PM CST Thu Jan 18 2018

/06z TAFs/

No major changes from previous TAFs with predominantly VFR
conditions expected through the overnight hours and into Friday.
The one exception may be at the Waco TAF site where cigs could
briefly dip below 3 kft around daybreak, but otherwise, cigs
around 3-4 kft can be expected. Metroplex TAF sites can expected
continued periods of stratus around 4-5 kft and an increase in
high clouds from an approaching upper disturbance. Winds will
remain out of the south around 10 kts overnight before increasing
in speed by midday Friday; some gusts around 20 kts are possible.

Late Friday afternoon and evening, an increase in low-level
moisture should result in the arrival of widespread MVFR cigs.
Conditions should begin deteriorating at Waco as early as 21z and
at DFW area airports after 00z. Initially, cigs will likely be at
or above 2 kft, but they`ll quickly drop to around 1 kft during
the evening hours. Periods of IFR conditions may also occur, but
have not included any mention in the extended DFW TAF yet. In
addition to lowered cigs, some vsby-reducing mist or drizzle will
also be possible, although the greatest potential for these
conditions seemingly lies east of I-35 at this time. Prolonged
MVFR or even IFR conditions can be expected through much of
Saturday as well.



.UPDATE... /Issued 837 PM CST Thu Jan 18 2018/
Made a few adjustments to the ongoing forecast to account for
observed trends in cloud cover and temperatures. Satellite data
shows a few areas of cloud cover. The first is the cloud deck
which was over much of the area around 00Z. This cloud deck is
advecting eastward for the most part. This will enable much of
the region tonight to see mostly clear or partly cloudy skies for
the majority of the night. The second area is a deck of high
cloud cover, streaming in from the northwest.

The third area observed on satellite and radar, is a disturbance
moving through the upper level trough. This disturbance is located
near Austin at 02Z, and will continue to move slowly northeast
and east overnight. A few observation sites in Central Texas have
reported brief light rain, so a few light showers are possible
across our far southern areas, especially Bell, Milam, Robertson
and Leon Counties. However, the extremely dry air at the surface
will likely keep widespread rain from ever reaching the ground.
Have therefore kept out the mention of rain in the forecast
update, yet it does remain a low possibility.



.SHORT TERM... /Issued 347 PM CST Thu Jan 18 2018/
/Tonight through sunrise Friday/

Main weather concern during the short term time period will be
the areal coverage of cloud cover and its impact on overnight low
temperatures. Otherwise, tranquil conditions are anticipated.

Satellite and surface observations this afternoon indicate that
the initial surge of shallow, low level moisture continues to
stream northward. This moisture appears to be centered around
850-925mb as evidenced in RAP soundings across the area. Flow
within and just below this layer will increase this evening and
into the overnight hours in response to pressure/height falls
across the upper midwest. The increase in low level flow coupled
with an increase in low level moisture should lead to "warmer"
overnight conditions with most areas falling into the 20s and 30s
areawide. A few of the sheltered/low lying areas may fall into the
upper teens, however. The low level flow will also help to
transport additional moisture and stratus northward. While there
is some uncertainty in the northern extent of the cloud shield, it
looks like a guarantee for mostly cloudy skies down across
eastern and southeastern zones. As a result, I`ve kept
temperatures a little higher across this part of the FA with
readings near or just above freezing. The breezy conditions just
above the surface should mitigate any potential for fog, but if
moisture deepens enough, there may be a few sprinkles or drizzle.
For now, this threat is too low to include in the forecast.



.LONG TERM... /Issued 347 PM CST Thu Jan 18 2018/
/Friday through Thursday/

Friday morning will start out considerably warmer than the
previous few mornings with most areas near freezing, but southerly
winds well established. Cloud cover that has spread over the
region this afternoon will thin some overnight, although thicker
low cloud cover associated with a slug of deeper moisture will
spread north overnight primarily affecting the southeast counties.
This is likely to persist through the day Friday and will hamper
a more significant warmup across the eastern and southern parts of
the CWA. Highs on Friday are likely to remain in the upper 40s
and lower 50s across the southeast tomorrow while areas farther
north and west warm into the lower 60s. The increase in moisture
atop some already cool air in place will likely result in some
areas of light rain or drizzle late Friday night into Saturday
morning, especially east of I-35.

By Saturday, a strong upper trough will dig into the southwest
U.S. resulting in surface pressure falls across much of the
Central Plains. Southerly winds will increase in response and
continue to transport moisture northward. A few areas of light
rain or showers may develop mainly east of I-35 where we`ll have
20% PoPs. Strong southwest winds above the surface will aide in
warming with highs expected to climb into the 60s and lower 70s.
The extensive low clouds will also be accompanied by very low rain
chances overnight Saturday night.

By Sunday, as the upper trough ejects into the Central Plains, a
Pacific front/dryline will advance eastward into North Texas. Low
level flow will veer rather quickly during the late morning hours.
Despite strong forcing for ascent spreading across the region, the
veering flow and relatively weak lapse rates will result in little
instability across North Texas. Showers and a few thunderstorms
may develop by midday into early afternoon mainly east of I-35.
We`ll have PoPs at 50-70% for areas mainly east of I-35 Sunday
afternoon. The lack of instability and quickly veering flow should
result in a relatively low severe weather threat. Any
precipitation should quickly end from west to east Sunday evening.

After the passage of the front, we should enter a period of
relatively quiet weather next week with high pressure settling in
through mid week and temperatures just slightly above normal.
We`ll be watching another strong upper trough dig into the western
U.S. toward the end of next week which could bring additional rain
chances to the region.



Dallas-Ft. Worth    32  57  47  68  55 /   0   0  10   5  20
Waco                29  54  45  70  55 /   0   0  20  10  20
Paris               26  53  43  65  54 /   0   0  20  20  20
Denton              27  59  46  69  54 /   0   0   5   5  10
McKinney            25  55  45  68  54 /   0   0  20  10  20
Dallas              32  57  49  68  56 /   0   0  20  10  20
Terrell             28  53  47  68  54 /   0   0  20  20  20
Corsicana           28  51  48  68  55 /   0   0  20  20  20
Temple              29  52  46  70  54 /  10   5  20  10  20
Mineral Wells       27  63  43  72  51 /   0   0   0   5   5




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