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

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175
FXUS64 KFWD 252320
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
620 PM CDT Sat Mar 25 2017

.AVIATION...
Winds will become light and variable toward sunset and then
southerly later during the evening as a surface high moves off to
the east. Low clouds and areas of fog are expected to develop
across South Texas overnight tonight and some low clouds may
spread north into the Waco area by 12z and into the Metroplex TAF
sites after daybreak. Thus have indicated a TEMPO BKN015 at KACT
from 12 to 16z and a TEMPO BKN020 at the Metroplex TAF sites for
the 13 to 16z period.

Southerly winds will be on the increase Sunday as a lee side
trough deepens. Expect south winds 10-12 knots at 13z to increase
to 15-17 knots by 16z with some gusts of 25 knots possible through
the afternoon. Although a capping inversion will be in place,
isolated to scattered thunderstorms may form along the dryline by
mid afternoon along and north of the I-20 corridor. Thus have
placed VCTS in the Metroplex TAF sites for the 21z through 00z
period.

58

&&


.PREV DISCUSSION... /ISSUED 400 PM CDT Sat Mar 25 2017/
Mostly sunny skies and pleasant temperatures prevail across North
Texas behind last night`s cold front. West-northwest winds have
ushered in some drier air making for a nice day across the region.
Temperatures are generally in the 60s and 70s with dewpoints in
the 40s.

Springtime usually means rapidly changing weather as the upper
pattern is usually fairly progressive. Tomorrow will be no
different. Shortwave ridging today and tonight will give way to a
fast moving shortwave trough by tomorrow and increasing severe
weather chances. As the upper disturbance approaches, rapid
surface cyclogenesis will commence during the morning hours. This
will result in strengthening southerly flow and a rapid northward
transport of moisture. By midday, surface dewpoints will likely
be near 60 degrees along the I-35 corridor toward to the Red
River. In addition, a dryline will advance eastward across West-
Central Texas.

By late afternoon, an elevated mixed layer will be in place across
North Texas resulting in a capping inversion around 800mb with
very steep lapse rates through about 500mb. Even as the main
shortwave tracks across northern Oklahoma, stronger forcing for
ascent will spread into North Texas by late afternoon. This should
help to lift the capping, which is not expected to be overly
strong. We`ll likely sample this with supplemental balloon data
tomorrow afternoon. The bigger concern regarding convective
development will be the quality and depth of moisture return into
the area given the northerly track of the shortwave. Surface based
instability is expected to be around 2000 J/kg with dewpoints in
the lower 60s, although this moisture is fairly shallow. Mean
layer instability (around 1500 J/kg) will likely be more
representative of the environment tomorrow afternoon from the
Metroplex and areas southward. Most of the high resolution
guidance develops convection to the west-northwest of the
Metroplex by 22Z, although these initial convective attempts
quickly diminish by 00Z. This suggests that the initial
development along the dryline may not have enough support to allow
them to move off the dryline into a more unstable environment.
Forcing will be stronger the farther north, so areas generally
north of I-20 should have a better chance for thunderstorms
through the early evening hours.

Our latest thinking is that the best chance for severe
thunderstorms in our area will be in the Red River counties,
particularly Cooke, Grayson, and Fannin counties, from about 22Z
to 00Z. However, it should be noted that if any storms farther
south can be sustained, then the environment is more than suitable
to support severe weather. Forecast soundings for tomorrow
afternoon feature lapse rates in excess of 8 C/km through a deep
layer along with large clockwise curved hodographs through the
lowest 2 km. While all modes of severe weather will be possible,
the quality/depth of moisture remains the biggest limiting factor
for a more appreciable tornado threat. Very large hail (baseball
size or larger) will be the main severe weather threat through the
evening hours. We`ll maintain 20-30% PoPs across mainly the
northern half of the CWA with the best chances along the Red
River. Any convection that develops will move east through the
evening with a cold front moving into the area during the
overnight hours.

Monday looks like it will be a rather nice day behind the cold
front but it won`t last long. Another strong upper low will
move into the southwest U.S. by Tuesday. This will again allow
moisture to spread northward and rain/storm chances increasing
late Tuesday through Wednesday. There may be an initial severe
weather threat late Tuesday afternoon/evening as convection
develops across West Texas along a dryline and moves eastward.
Rain/storm chances increase significantly across North Texas
Tuesday night into Wednesday where one or more rounds of
thunderstorms may move through the region. At this time, the
severe weather threat does not look overly impressive, although
there will be sufficient instability/shear to support rotating
storms during this time. We`ll monitor this closely over the next
48 hours. Heavy rainfall will be possible through Wednesday with
current forecast rainfall amounts between 2 and 4 inches across
parts of North Texas. While the system looks like it will remain
progressive enough to preclude a more significant flash flood
threat, localized training of storms would support flash flooding.

This system moves east Wednesday night into Thursday with quiet
weather through the end of the week.

Dunn

&&



.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    55  84  60  80  56 /   0  30  20   0   0
Waco                54  83  62  83  59 /   0  20  20   0   5
Paris               50  80  60  77  53 /   0   5  50   0   0
Denton              51  82  58  78  53 /   0  30  20   0   0
McKinney            49  81  59  78  54 /   0  30  30   0   0
Dallas              55  84  62  81  57 /   0  30  30   0   0
Terrell             50  82  62  79  56 /   0  20  40   0   0
Corsicana           54  84  63  82  60 /   0  10  30   0   0
Temple              54  84  60  84  60 /   0   5  10   0   5
Mineral Wells       52  86  54  80  53 /   0  20  10   0   0

&&

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

$$

58/24



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