National Weather Service Raw Text Product

072 
FXUS64 KFWD 181617 AAB
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1117 AM CDT Mon Jun 18 2018


.UPDATE...
Overall, the inherited forecast is still on track and only minor
adjustments were needed for the morning update. A surface low
located near the Texas Coastal Bend is producing widespread rain
all along the Texas and Louisiana coasts. However, only isolated 
to scattered light showers have been observed across North and 
Central Texas so far this morning. An extensive cloud deck covers 
the region but breaks are observed in the coverage. These breaks 
will provide heating of the moist boundary layer below which is 
expected to result in an increase of convective activity this 
afternoon. Showers and isolated thunderstorms are expected to be 
most numerous south of I-20 and east of I-35 as some of the 
activity in SE Texas may also move into this area. Gusty winds, 
heavy downpours, and lightning will continue to be the main 
hazards with showers and storms through the early evening hours.

For the update, made a few minor adjustments to the high
temperatures and location of PoPs based on latest trends.

JLDunn

&&


.AVIATION... /Issued 729 AM CDT Mon Jun 18 2018/
/12Z TAFS/

Tropical moisture has arrived, as evidenced by the multiple cloud
layers from the boundary layer to 800mb on this morning's 
sounding and CAMs forecast soundings. The main player in aviation 
weather the next 24-30 hours will be the weak Western Gulf of 
Mexico low that is expected to move inland by tonight from the 
Texas Coastal Bend to the Lower Texas Coast. This is a broad and 
weak system with our area on the northern fringe of its' effects. 
With the rich tropical moisture in place, which is at maximum for 
mid June, the main challenges will be timing MVFR/VFR cigs and 
convective chances across all North and Central TX airports. 

For all airports, will prevail low VFR cigs BLO FL040 through 
late morning, as the boundary layer has remained semi-mixed 
through the pre-dawn hours into daybreak this morning. There is 
rich enough moisture within the boundary layer to advertise a 
TEMPO group of MVFR cigs through 15z-16z. By afternoon, all 
airports will see varying VFR cigs AOA FL040 with heating and 
mixing. In addition, strong insolation will likely result in 
isolated instances of TS around DFW and scattered TS near Waco 
this afternoon, but SHRA will be more the prevailing impact. 

As such, have only continued to advertise VCSH at all airports 
due to the tropical environment in place. Though a few rumbles of 
thunder or lightning strikes are possible this afternoon through 
nightfall, the skinny CAPE in place has me foregoing any mention 
of TS in the current TAFS. Since any definitive upper level or 
surface boundaries are expected to be mostly absent, trying to 
define confidence periods for TS occurrence was very difficult. 
Confidence is just too low to try to accurately depict time 
periods for TS, even at Waco Regional Airport where coverage 
should be higher both this afternoon and overnight. 

East-southeast winds will continue through the daytime hours and 
will be near 15 knots with gust to around 20 knots. After sunset, 
sustained winds will drop down to around 10 knots. In addition, 
arrivals/departures may be impacted due to weather specifically at
the BYP/CQY cornerposts and SBND/EBND air traffic due to the 
periodic convection.

05/

&&

.SHORT TERM... /Issued 358 AM CDT Mon Jun 18 2018/
/Today Through Tonight/

Tropical moisture in advance of a weak system over the West-
Central Gulf Of Mexico continues to surge northward across the 
CWA, especially areas east of U.S. 281 per GOES-R Total 
precipitable water(PWAT) data and area soundings this past 
evening. PWAT values per the GOES-R sounder indicate values around
or near 2 inches south of I-20 and east of I-35, with values 
1.6-1.9 inches further north and west. The surge of moisture was 
being support by deep east-southeast low level flow, as noted by 
30-35 knot southeast winds on area 88D VWP profilers. So if you're
noticing it's become noticeably more humid the past 24 hours, you
are correct in your assessment considering the very rich and well
above normal surface dew point temperatures in the lower to mid 
70s across much of the area. Look for the very humid, even muggy 
conditions to continue through much of the week.

The weak Western Gulf system will continue moving inland along 
the Texas Coastal Bend and Lower Texas Coast through tonight. With
a mid level disturbance lifting northeast across the Central and 
Southern High Plains today, our area will be in somewhat of an 
area of mid level deformation, or subtle elevated frontogenesis. 
Currently, the area was pretty much devoid of any precipitation 
early this morning, as we remained underneath the far southwest 
part of an mid level high pressure centered over MS/AL. Widespread
stratus has already overspread much of the area early this 
morning with more in the way of cloudiness expected across 
especially the southeast half of the CWA due to the tropical 
environment in place. Showers were already moving northwest and 
onshore across the Upper Texas Coast into Southeast Texas and 
should become scattered in nature across our Central Texas 
counties through the morning hours, with more isolated coverage 
further north as diurnal heating begins ramping up later this 
morning. 

As we continue to heat up into the upper 80s and lower 90s (mid 
90s far northwest) this afternoon, some skinny CAPE values within 
our increasing moist-adiabatic profile should become realized with
potential for occasional rumbles of thunder occurring during the 
afternoon hours. With our Central Texas counties being closer to 
mid level shortwave energy rotating up north up through Southeast 
Texas, will have a gradient of higher rain chances across Central 
Texas and our far east/southeast counties. Further north and west,
any isolated convection will be more result of strong insolation,
and the occasional outflow boundary that may result from any late
morning development. The tropical environment will likely mean 
any convective development will be capable of brief very heavy 
downpours. Further northwest along the periphery of the deeper 
tropical moisture, gusty winds could occur with stronger cells 
where relatively more mid level dry air could provide brief 
evaporative cooling. Otherwise, lightning strikes will be concern 
for anyone outdoors for any amount of times. East-southeast winds
will continue on the breezy side per aforementioned strong 925mb
wind fields with 15-20 mph common across much of the area with
higher gusts, which should help in some relief from the very humid
conditions. 

Tonight -- we should continue to see scattered coverage of
rainfall across our far southern Central Texas counties, with
isolated coverage continue elsewhere through sunset. Loss of
strong heating afterward should result in more isolated coverage 
of mainly showers through midnight Tuesday. Coverage is expected 
to increasing across especially our eastern Central Texas counties
overnight, as a spoke of shortwave energy rotating west and well 
north of the landfalling, weak Western Gulf disturbance provides 
large-scale ascent to a very rich and moist environment. No severe
weather is expected and much of the activity should be in the 
form of off/on heavy shower activity, though will have embedded 
thunder added in across Central Texas. It's possible some minor 
street flooding could occur across these areas by sunrise Tuesday,
but with soils very capable of absorbing rainfall at this time, 
we do not expect any major or widespread flooding issues. 
Otherwise, look for breezy southeast winds to continue with lows 
in the 70s. 

05/

&&

.LONG TERM... /Issued 358 AM CDT Mon Jun 18 2018/
/Tuesday through the Weekend/

Rain and isolated thunder chances will be the main theme in the
long term portion of the forecast period. As has been noted in
previous AFDs, rain chances will be generally highest during the 
daytime hours with a lull in precipitation during the overnight 
hours, at least through mid-week. Towards the end of the week, 
there will be rain chances during the morning hours mainly along 
the Red River and across the Big Country...as well as afternoon
rain chances across East Texas.

Tuesday and Wednesday---Rain and isolated thunderstorms will
continue on Tuesday morning, though it's possible that immediately
following sunrise that most areas remain rain-free. As diabatic 
heating increases through the day, showers and isolated 
thunderstorms should proliferate---mainly south of I-20. 
Convection will be possible farther north, but at this time the 
chances do not look great. A broad inverted surface trough may 
help to focus more widespread convection down across the Brazos 
Valley and 50 to 60% PoPs seem appropriate here. I can't rule out 
a brief window of some heavy rain across the Brazos Valley, but 
antecedent conditions do not appear to support much in the way of
significant flooding. However, there could be some minor water 
issues here if convective activity trains given the high PWATs and
nearly moist-adiabatic forecast sounding profiles. As has been 
advertised over the past several days, daytime high temperatures 
will be in the 80s and 90s, but it'll be quite humid as dewpoints 
in the upper 60s and 70s are forecast.

Rain chances should diminish during the overnight hours into
Wednesday and I've reduced PoPs down into the 20 to 30 percent 
range as diabatic heating is lost. I can't rule out a few showers 
associated with the core of the surface trough/low down across 
Central and southern parts of East Texas, however. Areas closer to
the Red River should see mostly rain-free conditions. 

For Wednesday, the 00 UTC GFS continues to advertise that a broad
mid-level trough/shear axis will develop across the Texas Coastal
Plain and swing northeastward. The 00 UTC NAM and 00 UTC ECMWF 
now follow the GFS solution and amplifies this feature though the
day. The degree of large scale ascent associated with this 
trough/shear axis is in question, but it's presence is enough to 
increase the areal coverage of likely PoPs across Central and East
Texas through the day on Wednesday. If large scale ascent is 
stronger, then higher PoPs will be needed across East Texas. 
Depending on how much rain falls Tuesday, there could be a very 
minor flood threat across the Brazos Valley and adjacent parts of 
East and Central Texas. Similar to Tuesday, rain chances will 
diminish after sunset across most areas. At this time, we will be
monitoring for possible convective development upstream across 
the Panhandles and southern Kansas. The GFS's QPF max across the 
Big Country looks a little suspicious at this time and is probably
erroneous due to convective feedback. I'll keep the inherited 
slight chance to chance PoPs across the northwest given the 
conveyor of higher theta-e, however. 

Thursday and Friday---The forecast uncertainty increases Thursday
and into Friday, as a majority of the forecast will depend on 
mesoscale processes that are simply too difficult to forecast at 
this juncture. What is appearing more likely is that a decent 
anticyclonic jet for this time of year will nose in from the 
northwest. This will induce a compact surface low along the 
Kansas/Nebraska border. This surface low should drag a front 
southward and new model guidance suggests that it may even make it
into parts of North Texas. I'll trend towards climatology, 
however, and keep the front just north of our Red River counties 
in forecast wind fields until run-to-run consistency increases. 
What is certain, however, is that the synoptic background (lift, 
moisture and instability all in place) will support thunderstorm 
development along this frontal boundary. How far south this front 
and thunderstorms make it is uncertain, but the northwest flow and
instability axis would support a propagation of storm complexes 
southward towards North Texas. With these factors in mind, I'll 
maintain slightly higher PoPs along the Red River on Thursday and 
Friday mornings with lower PoPs towards and south of the I-20 
corridor. During the afternoon hours on Thursday and Friday, 
slight chance to chance PoPs remain across East Texas where there 
may still be some influence from the diffuse mid-level trough 
(though if it moves farther east, parts of our area may be beneath
subsidence). 

The Weekend---Probabilistic guidance suggests that a flat H5 
ridge will set up across our area keeping much in the way of 
synoptic scale forcing to the north of our area. Thus, I've kept 
the weekend forecast dry. However, the zonal flow across Oklahoma 
and Kansas in addition to what should be a decent pool of low 
level moisture and daytime heating, there will be more 
opportunities for daily convection. This convection may attempt to
make a run at some of our Red River counties and if this appears 
more likely, PoPs will need to be included in latter reaches of 
the long term forecast.

24

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    90  76  86  74  88 /  20  10  30  10  40 
Waco                88  74  84  73  87 /  40  40  50  20  50 
Paris               87  72  87  71  86 /  40  10  40  20  40 
Denton              90  75  87  73  88 /  20  10  30  10  30 
McKinney            88  72  86  72  87 /  30  10  30  20  40 
Dallas              90  76  87  74  88 /  30  20  40  20  40 
Terrell             88  74  86  73  87 /  40  20  40  20  50 
Corsicana           87  73  84  73  86 /  40  50  50  20  50 
Temple              86  72  83  72  85 /  40  50  60  30  50 
Mineral Wells       91  73  85  72  89 /  20  10  20  10  20 

&&

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

$$

82/92