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

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FXUS64 KFWD 232048
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
348 PM CDT MON MAY 23 2016

.DISCUSSION...
A special early afternoon sounding nicely depicted the subsidence
drying and strengthening cap that occurred in the wake of this
morning`s convective system that tracked across the northern
zones. The stronger cap will have implications on the forecast
tonight as almost all guidance indicates it should hold strong.
However this same guidance indicates some convection occurring
across either the western or northern zones this evening and
overnight. Obviously this convection will be elevated above the
cap where the atmosphere will contain sufficient instability for
thunderstorms due to extremely unstable lapse rates of almost 9
deg C per km. Since this convection will not have access to the
very unstable surface air, it will tend to temper the severe
weather threat with just marginally severe wind/hail possible over
the region. Otherwise some very light showers below the capping
inversion will occur due to unseasonably strong moisture
advection which has already been responsible for the thick cloud
cover and drizzle this afternoon west of I-35.

Water vapor loop shows a shortwave trough moving through the Big
Bend region at this time and it appears most of the model guidance
has identified this feature. As forcing for ascent occurs ahead
of this shortwave, scattered thunderstorms will fire along the dry
line across West Texas and the Texas Panhandle. This activity
should move to the east faster tonight than last night, likely
because it will become elevated above the capping inversion and
move only with regard to the mid level mean flow. While I don`t
anticipate an MCS to develop out of this activity and affect our
region, the presence of anvil precipitation seeding the unstable
mid level atmosphere with moisture out ahead of the storms will
allow scattered and mostly disorganized convection to also quickly
develop eastward. Model guidance has some wildly varying QPF
solutions, but in general the consensus has focused on the
northwestern and northern zones for the most favored area tonight
beginning around 9 pm and tracking eastward through the early
morning hours. This is the region where mid level warm advection
and lift is strongest and it makes sense to be the favored area
for scattered convection. The highest pops of 40 percent will be
featured across this area, with 30 percent down to I-20, and 20
percent across the southern half of the CWA. Since convection in
our area is highly dependent on the scope of the dry line
convection out west, there is a very real possibility that the CWA
will stay dry tonight. Therefore have kept the PoPs on the lower
side due to the lower confidence.

The departing shortwave trough Tuesday morning will ensure another
round of subsidence in its wake tomorrow. The cap will again be
strong, but due to steep mid-upper level lapse rates there is the
possibility of another round of elevated convection Tuesday night
primarily over the northern zones. A low severe wind/hail threat
will exist with this activity. Otherwise another mostly cloudy,
warm, and humid day will be the rule with lows in the low 70s and
highs in the mid 80s. The cap will intensify further on Wednesday
and therefore we will keep the forecast dry despite a very unstable
airmass developing over the region as high temps reach the low
90s west to mid 80s east. Wednesday looks to be the warmest day of
the week with the high humidity pushing the heat index into the
upper 90s.

Rain chances increase Thursday as an unseasonably strong shortwave
trough begins to move toward the region. This system will take an
unusually far southern track for late May and therefore will
provide the forcing to lift and erode the capping inversion over
the area by Thursday afternoon. The very moist and unstable
airmass in place will be allowed to utilize its potential energy
in the form of what will likely be vigorous convection. Meanwhile
shear profiles will increase ahead of this upper level system
enough to support supercell convective modes. High precipitable
water values of up to 2 inches, strong 30-40 kt low level flow,
and diffluent thickness contours all point toward an increasing
risk of widespread heavy rain and flooding. These synoptic
dynamics for rain and storms look favorable from Thursday into
Friday afternoon. While it is tempting to get into the details of
a severe weather forecast, it is a bit early to do so at this
time. There could be copious mid level moisture and elevated
convection that would limit the overall severe weather threat. In
addition there is a concern that the vigorous convection may tend
to develop more across South Central and Southeast Texas as the
ECMWF shows which would intercept the best moisture/instability
across North Texas. So while there`s forecast skill to say that a
significant severe weather and heavy rain event may be looming in
the general region by the end of the week, it is too early to say
whether this will definitely impact our CWA or not. Either way it
will be the focus of our attention over the next few days.

Otherwise height rises and diminished moisture/instability in the
wake of this system will likely ensure a dry Saturday, but low
chances of storms will creep back into the forecast Sunday and
Memorial Day as shortwave troughs continue to ripple through in
southwesterly flow aloft. Temperatures by the weekend will be
warm with temperatures in the upper 80s for highs and lows in the
low to mid 70s. Don`t worry plenty of humidity will be available
to make Memorial Day feel like summer.

TR.92

&&

.AVIATION...
/ISSUED 120 PM CDT MON MAY 23 2016/
The thunderstorm complex that moved across areas mainly north
of I-20 this morning had moved off to the east. Ceilings have
improved to VFR in the Metroplex and these conditions will likely
continue through the afternoon into the evening hours. MVFR
stratus should spread back into the TAF sites 04-05z. Although
not mentioned in the TAFs, some of the computer guidance does
indicate IFR conditions developing around 05z and then continuing
through 18z Tuesday. There are very low chances of thunderstorms
late this afternoon into early evening, but with the capping
inversion in place these chances are way too low to include in the
TAFs. There will also be a low chance of thunderstorms
around/slightly after daybreak Tuesday if thunderstorms that are
expected to develop along the dryline in West Texas late this
afternoon manage to work their way toward the Metroplex, but
chances at the Metroplex TAF sites are too low to include at this
time.

MVFR ceilings will prevail through this afternoon across the Waco
area with periods of high end ifr. Expect more widespread IFR
conditions to develop late during the evening and then prevail
through midday Tuesday. Some borderline LIFR may occur 10-14z
with a combination of low ceilings and patchy fog.

58


&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    73  85  73  90  74 /  30  10  20  10  20
Waco                73  86  73  88  74 /  20  10  10  10  20
Paris               69  83  70  86  73 /  30  20  20  10  10
Denton              71  84  71  90  74 /  30  10  20  10  10
McKinney            71  84  71  88  74 /  30  10  20  10  10
Dallas              73  86  73  89  75 /  30  10  20  10  20
Terrell             70  86  72  89  74 /  20  10  20  10  10
Corsicana           71  86  73  87  74 /  20  10  10  10  20
Temple              73  86  73  88  75 /  20  10  10  10  20
Mineral Wells       73  84  71  90  73 /  40  20  20  10  10

&&

.FWD Watches/Warnings/Advisories...
None.
&&

$$



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