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

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230
FXUS64 KFWD 211842
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
142 PM CDT Tue Mar 21 2017

.AVIATION...
VFR through the evening with a mainly clear sky. Stratus will
form over South Texas and the Hill country late this evening with
the development of a 35 knot low level jet. Low MVFR to IFR
ceilings will reach Waco around 08Z and the Metroplex TAF sites by
12Z. The low ceilings will slowly lift through the morning and
eventually scatter by Wednesday afternoon.

A south wind will prevail through Wednesday morning at speeds
between 10 and 15 knots along with some higher daytime gusts.

79

&&

.UPDATE...
Main update this morning was to add in a low chance for a couple
of showers and/or storms out across far western zones for this
afternoon and early evening. Also updated hourly temperatures and
dewpoints to be more in line with observations. Otherwise, the
remainder of the forecast is in good shape.

Satellite imagery this morning revealed a large ACCAS field
across the Big Country with radar imagery actually detecting a few
echoes. While these echoes are likely based at around 11,000 feet
or higher, steep lapse rates, per the 12 UTC FWD RAOB, coupled
with hot conditions may allow for the development of one or two
elevated convective elements. The latest HRRR and to a degree the
TTU WRF indicate that there is enough potential for some high
based convection and I went ahead and added a 15 PoP mainly for
areas along and west of a Hamilton to Palo Pinto to Bowie line. I
wouldn`t be surprised to to see some gusty winds given the high
based nature of convection and subsequent in and sub-cloud
evaporative effects. Rain amounts will be low due to the high-
based nature of the activity.

In addition to the mention of thunder, nudged sky conditions
upward out west and lowered afternoon dewpoints based on trends.
Our max temperatures still look reasonable, so no changes were
made to that part of the forecast. Updated products have been
transmitted.

24-Bain

&&

.PREV DISCUSSION... /ISSUED 410 AM CDT Tue Mar 21 2017/
A quick analysis of the weather pattern this morning shows a cold
front draped from the Texas Panhandle into Northern Oklahoma
early this morning. Meanwhile, over North-Central Texas, it was
breezy and mild under variably cloudy skies with temperatures in
the 60s, except lower 70s across immediate urban areas. The strong
ridge aloft was breaking down somewhat in areas north of I-20, as
progressive shortwave energy moved east-southeast along the
Kansas/Oklahoma border. Current low level water imagery (7.3
microns) indicated the strong EML from south of I-20 into the
Upper Texas Coast.

As the shortwave aloft over the Kansas/Oklahoma border shunts
eastward over the Mid Mississippi Valley, subsidence behind this
feature over the Central and Southern Plains will assist in
advancing the cold front southeast toward the western Red River
Valley late this afternoon. Strong heating and mixing ahead of the
cold front should slow it down or stall it in the vicinity of our
far northwest counties. A surface dryline will be anchored west
of our CWA. A few high-res models hint at some brief isolated
convective activity possible west of Highway 281 between 4 and 7
pm CDT, but not all show this. Environmental analysis shows our
elevated mixed layer (cap) will be strong with only surface
forcing near the triple point of the cold front and dryline just
west of our CWA. With forcing being limited, the strong cap in
place, and moisture fairly limited, have decided to leave the
isolated storms out of the forecast. This reasoning was
collaborated with NWS offices to our west and northwest. However,
this area will be monitored late today, as any activity would be
high-based and could briefly be strong-severe. As of now, it does
not look promising and would be very high-based. Highs will warm
into the upper 80s/lower 90s across this area once again. That
said, no records will be threatened today at DFW, as today`s
record is 100 degrees set in 1916.

The cold front does appear to remain stalled tonight near or within
our Red River counties and far northwest counties. Another
shortwave disturbance tracks east-southeast in the progressive
mid level flow well north of the Red River. This may result in a
small cluster or nocturnal MCS across central/eastern Oklahoma
overnight tonight that tracks southeast toward the ArkLaTex
toward sunrise Wednesday morning. This area of convection is
expected to weaken as low-level wind fields veer and weaken toward
sunrise. In addition, the capping inversion aloft should remain
entrenched south of the Red River, this will leave out low
convective chances across the northeast counties between 3-9 am
Wednesday morning. Otherwise, Wednesday will continue warm and
breezy, though not as hot and more humid with the Gulf of Mexico
opening up and surface dew point temperatures in the 60s surging
into the area. The upper ridge over the area will strengthen
across the Southern Plains Wednesday night through Thursday
evening, in advance of our vigorous system developing across the
Western U.S. As a result, breezy, warm, and humid conditions will
continue with no rainfall expected.

As expected in previous days, the models have slowed down 6-12
hours with the deep mid level energy. A surface dryline will
deepen and remain well west of the area Thursday night. Initial
discrete convection will likely develop along the dryline across
far West Texas late Thursday evening. This activity will likely
congeal into a broken line of storms, or possibly a squall line,
after midnight and move east with the large-scale ascent into
western North-Central Texas through daybreak Friday morning. As
the upper low lifts in a negative fashion northeast over northern
Oklahoma and southwest Kansas, large-scale ascent will increase
across much of the area on Friday, with widespread showers and
thunderstorms occurring across much of the area. Due to the time
of day, much of this activity could be elevated, though a strong
to marginally severe storm will be possible. That said, it`s hard
to determine how much the environment will be corrupted by morning
convection.

If areas along and east of I-35 can partially break out and
destabilize enough Friday afternoon, then there would be a risk of
severe weather with ascent combining with rich moisture and
moderate instability. The main threats at this time would be
damaging winds and large hail. The tornado threat at this time
looks very limited, as wind profiles only veer slightly just
above the surface, before backing above 850mb. In addition, though
conditional, areas west of I-35 should warm up in behind the
advancing cluster of showers and storms. This area may see a high
fire danger. However, at this time earlier rains and some early
spring green up should limit the threat. If convective rains are
more spotty than expected, then fire concerns may be warranted.

A broken line of storms will linger across the far east-southeast
counties Friday evening with a continued risk for a few strong to
possibly severe storms, before a cold front clears things out in
time for the beginning of the weekend. The area will enjoy a day
of cooler and drier weather Saturday with highs in the 70s to
near 80 degrees across Central Texas. However, this reprieve will
be short-lived as strong lee cyclogenesis occurs in advance of a
second shortwave trough expected to lift across the Central Plains
into Oklahoma Sunday night into Monday. Low humidity values and
warm high temperatures Sunday afternoon into the mid-upper 80s
west will likely result in another elevated-to-high fire danger.
This second vigorous shortwave looks to move further north than
Friday`s system. That said, areas mainly north of I-20 could see
low chances for what should be elevated thunderstorms, which would
shift to our eastern counties Monday with a weak surface trough
or weak Pacific cold front. Slightly cooler temperatures will
return on Monday.

Afterward, a third vigorous system looks to organize to our west
or northwest for the early to middle part of next week. Right now,
medium range models and ensembles show a broad variance on
strength, track, and timing, with the European more progressive
than the slower and deeper GFS. Past history suggests that the GFS
is the more likely scenario with another thunderstorm evening
possible by late Tuesday night and Wednesday. Collaboration with
surrounding NWS offices agrees that a slower solution is the more
reasonable solution here. Rain chances were lowered after Monday
due to these uncertainties the first half of next week. Temperatures
next week will continue to be near or above seasonal normals for
late March.

05/



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    62  83  64  82  63 /   5   5   5   5  30
Waco                63  84  64  83  63 /   5   5   5   5  20
Paris               59  74  58  78  60 /  10  10  10  10  10
Denton              61  81  63  81  62 /   5   5   5   5  30
McKinney            61  80  62  81  61 /  10  10   5   5  20
Dallas              63  82  64  82  63 /   5   5   5   5  20
Terrell             62  80  62  82  62 /   5   5   5   5  10
Corsicana           62  80  63  83  63 /   5   5   5   5  10
Temple              61  83  64  84  63 /   5   5   5   5  20
Mineral Wells       61  83  62  83  60 /   5   5   5   0  50

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

79/24



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