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

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FXUS64 KFWD 220509
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1209 AM CDT Mon May 22 2017

.AVIATION...
/06Z TAFs/

Overnight rain trends remain challenging as one wave is now moving
through the region and additional showers and isolated
thunderstorms will likely continue to develop through the night.
Based on latest guidance, have decided to end the mention of
precipitation in the Metroplex at 09Z, but it`s possible this may
have to be extended through at least 12Z. At KACT, have left a
mention of rain through 11Z, but even this may also have to be
extended into the morning hours. For now, have also opted to leave
VCTS out of the KACT TAF, but if overnight trends indicate the
development of more thunder overnight, will have to include a
mention. The overnight round(s) of rain should end at the TAF
sites Monday morning, but additional showers or storms are
possible near DFW late Monday afternoon. As for another round of
storms Monday night, the latest guidance has slowed down the
timing and have removed a mention from the TAFs for now.

The wind direction this evening has been variable as a weak
surface low/MCV developed in the rain across Central Texas, but is
now moving into East Texas. For the Metroplex TAFs, will carry
VRB05KT for the start of the TAF period but eventually return them
to an easterly direction Monday morning, then southeast Monday
evening. For KACT, light north-northeast winds will continue for
the next few hours, and then northeast to east winds are expected
for the remainder of the TAF period.

The ongoing rain trends and MCV has impacted ceiling trends this
evening but still expect MVFR and IFR cigs to spread across the
region early Monday morning. Conditions will be slow to improve
and cigs are expected to largely remain in MVFR category for much
of the day. Some fog may occur at KACT overnight.

JLDunn

&&

.UPDATE...
Moisture appears to be surging north in advance of a shortwave
trough over South-Central TX. A swath of rain with occasional
embedded thunderstorms has moved into the southern-most counties,
warranting an increase to likely POPs for the 00-06Z time across
the southern few rows of counties. Clouds and precipitation have
kept temperatures down across the southern half of the forecast
area and hourly temp grids have been adjusted accordingly. The
south-to-north POP gradient will be kept for the overnight hours
with likely POPs across the south decreasing to slight chance near
the Red River. A break in the precip is expected during the day
Monday, then another disturbance will bring a chance of storms
(some possibly severe) Monday evening.

30

&&

.PREV DISCUSSION... /ISSUED 333 PM CDT Sun May 21 2017/
After a round of morning strong to severe storms in the vicinity
of the 850mb front and steep lapse rates aloft, a quiet period has
settled across the CWA in between shortwave disturbances. A
strong shortwave trough in the southern stream was seen on water
vapor imagery moving out of West TX and over the Upper Rio Grande
Plain and southern Hill Country as of this afternoon. Meanwhile,
the old surface cold front was draped along the I-10 corridor.

The surface cold front will remain south of the area through this
evening, before both it and the 850mb front begin their trek back
north as a warm front with the approach of the subtropical branch
shortwave over Southwest TX. Convective rain chances will increase
across our Central TX counties very late this afternoon and through
this evening. Thunderstorms, some possibly strong to marginally
severe will then expand north up through the I-20/I-30 corridors
later tonight through Monday morning, as the southern branch
shortwave trough moves across Central TX and enhances isentropic
ascent and elevated WAA above the frontal slope. A brief reprieve
is expected later in the morning and into mid afternoon Monday, as
this shortwave exits the area to the east. We will then await an
amplifying northern branch shortwave arriving from the northwest
later in the afternoon and even, at which time a second round of
storms will move southeast toward our northwest counties. There
will be the potential for strong to severe storms with large hail
and damaging winds. Any morning severe weather will likely be
associated with hail due to the elevated nature of convection with
the surface front to the south of the CWA. However, this surface
front will move north during the day and allow the area to be in
the warm sector by afternoon and add the damaging wind threat to
the equation.

By later Monday night/Tuesday morning, a cold front will move
into the region from the northwest, as yet another strong and
progressive shortwave disturbance arrives. Scattered showers and
storms will likely occur both in advance and behind the cold front
for another round of at least some strong storms. The environment
becomes more unclear at this point due to previous rounds of
convection and how much the atmosphere has been contaminated and
if re-charging can take place. We will continue to refine threats
for the late Monday night/Tuesday time period in future forecasts,
as it`s totally possible the morning MCS could really play a role
in evolution of frontal convective activity and the thermodynamic
environment during the afternoon hours Tuesday.

Afterward, convective chances come to an abrupt end on Tuesday
evening, as both the cold front and shortwave disturbance shift
southeast of our area. Brisk north winds will occur Wednesday,
before diminishing Wednesday evening with surface high pressure
settling in. Morning lows will be cooler with values in the 50s,
however, with the bulk of CAA remaining northeast of our area,
strong late May insolation will help heat the dry airmass in place
and allow for highs to rebound into the 70s to lower 80s.

Temperatures are expected to modify and warm up readily with the
arrival of shortwave ridging aloft and a return to southerly winds
Thursday through Saturday, especially the western half of the
region where low-mid 90s will make a return to the area. A broad
Western CONUS trough organizes next weekend, but bulk of the
stronger energy appears to remain north of the area. That said, a
few shortwave disturbances will move southwest to northeast across
the area during the Memorial Day Weekend into early next week. I
have have added low confidence slight rain chances through the
period. Either way, the modest west-southwest flow aloft will
likely enhance a relatively strong EML (cap) over the area than
even the medium range models are realizing, not to mention the
normal bias of these models being too weak and progressive with
the longwave trough to west and northwest. We should see better
upper-air sampling of this system as the week progresses, which
will help in refining the forecast with more confidence.

05/



&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    63  79  63  77  57 /  40  30  50  30   5
Waco                61  78  62  79  55 /  70  50  40  40  20
Paris               61  75  60  73  52 /  20  40  40  30  10
Denton              60  78  61  75  51 /  30  40  50  30   5
McKinney            60  77  60  75  54 /  30  40  50  30   5
Dallas              63  78  64  78  57 /  40  30  50  30   5
Terrell             60  75  62  76  55 /  50  40  40  30  10
Corsicana           61  77  63  78  55 /  60  60  40  40  20
Temple              61  78  62  79  55 /  70  60  40  40  20
Mineral Wells       60  78  60  74  51 /  30  30  50  30   5

&&

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

$$

82/30



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