816 
FXUS64 KFWD 101124 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
624 AM CDT Sat Aug 10 2019


.AVIATION...
/12z TAFs/

Concerns: Minor for TEMPO MVFR cigs BLO FL015 at Waco Regional 
Airport through 14z-15z, otherwise VFR with occasional mid-high 
clouds FL150-300. 

SSW flow at 25 knots right off the deck will have low MVFR cigs 
affecting Waco through mid morning, but otherwise VFR with strong
subsidence over all airports due to the strong upper high on top 
of the area.

All airports will see S winds 10-15 knots with a gust or two near
20 knots today, before winds go SE 10 knots or less after 00z
Sunday. Weather will be quiet, but very hot and breezy as a strong
upper high over the state keeps showers/storms well off to the
north and northeast through tonight.  

05/

&&


.SHORT TERM... /Issued 349 AM CDT Sat Aug 10 2019/
/Through Tonight/

Entering the beginning of the weekend, unfortunately, pretty much
more of the same. A stout upper high at 594 decameter will remain
centered right on top of North and Central Texas through tonight.
Another hot and humid day is in store for the area as highs warm 
to between the upper 90s and 103 degrees with a Heat Advisory 
continuing for the entire area this weekend for heat index values 
to/or exceeding 105 degrees. Breezy south winds will help a little
bit, but precautions should continue to be taken if you're 
expecting to be outdoors for any prolonged period of time during 
the heat of the day. 

Our area will be sandwiched between surface high pressure across 
the Western Gulf of Mexico and modest lee-side pressure falls 
across the Southern and Central High Plains for occasionally gusty
south winds 10-15 mph today, diminishing to around 10 mph 
tonight. There is a mid level disturbance dropping southeast 
across E OK/W AR and across the AR-LA-TX early this morning. There
is ample moisture near 700mb and lift from 25 knot SSW flow at 
925mb focusing across this area on the northeast periphery of the 
upper high. I expect a few sprinkles or even a brief shower or 
two northeast of a Gainesville to McKinney to Emory line this 
morning with these items in mind. Nothing significant weatherwise
or regarding rainfall amounts is expected with this activity 
considering time of day, high-based nature of activity, and 
brevity of occurrence this morning. 

Regarding fire weather, areas west of I-35 will mix out with than
areas further east. Afternoon humidity values in the west will
likely fall below 30 percent this afternoon. Winds will remain 
overall below 15 mph, but with rainfall lacking across this area 
recently and grasses/small vegetation continuing to cure, an 
elevated grass fire danger may be present this afternoon and we'll
continue to investigate if a grass fire danger statement may be 
need to be issued this morning for western parts of North and 
Central Texas. 

Tonight, the broken record of breezy, humid, and very warm 
conditions continue as temperatures will be very slow to fall 
considering the very warm boundary layer right above the surface. 
Low temperatures in the mid-upper 70s will be the rule across 
rural areas where more vegetation is present, while the high 
concentration of concrete across urban areas will retain the heat 
longer with lows only falling to between 80-85 degrees. No 
rainfall is expected tonight. 

05/

&&

.LONG TERM... /Issued 349 AM CDT Sat Aug 10 2019/
/Sunday through Friday/

As to be expected, heat will be the main story in the long term
forecast period. There does appear to be some *slight* relief from
the widespread triple digit heat Late Tuesday through Thursday. 
Thereafter, it appears that the widespread triple digit heat will 
return to North and Central Texas.

For the latter half of the weekend, the center of the 595 
decameter ridge will be centered across the Ark-La-Tex. This will 
equate to nil rain/storm chances as the mid and upper level airmass
over North and Central Texas will be very dry and subsident. Low 
level mixing will be absent across all but portions of the Hill 
Country and Sunday afternoon heat index values are expected to 
remain in the 105 to 110 degree range...easily validating the 
previously extended Heat Advisory. Most areas will top the century
mark, with a few locations across the higher terrain of the Hill 
Country remaining closer to 98-99 degrees. Regardless, it'll feel
very hot and with the plethora of late weekend outdoor 
activities likely, individuals should closely follow heat 
precautions and remain hydrated/cool with plenty of water.

The oppressive heat will continue into Monday and Tuesday as 
slightly stronger southerly flow ushers in a greater degree of low
level moisture. Blended guidance may be a little overzealous with
the degree of moisture transport, but heat indices may climb 
closer to 110 degrees for a good portion of the area. If trends 
continue and these 110 degree heat indices appear more plausible, 
Excessive Heat Watches/Warnings may be required. This will be 
particularly true near and east of I-35 (including the 
Sherman/Denison...D/FW Metroplex and Waco areas). 

On Tuesday, however, the upper level pattern will start to change
as the ridge axis will be shunted southward and become oriented 
from the Permian Basin to the Big Country by a deepening 
shortwave trough across western parts of the South Plains. This 
should give birth to a compact surface low with an attendant 
surface front that will move east and southeastward through 
Oklahoma and North Texas. Model guidance diverges significantly 
during this portion of the long term forecast period and this 
results in a low confidence forecast. The ECMWF has shown some 
run-to-run consistency with its depiction of synoptic features 
late Tuesday into Wednesday. It advertises that a diffuse frontal 
boundary will sink south of the Red River with very little fanfare
initially. As low-level convergence increases beneath the far 
northeastern flank of the H5 ridge across western North Texas, 
nocturnal convective initiation (Tuesday Night into Wednesday 
Morning) is forecast. Showers and storms are then forecast to 
become a bit more numerous through the day on Wednesday and roll 
east and southeastward around the northern periphery of the mid- 
level ridge. The ECMWF maintains a slightly wetter pattern through
Thursday as it keeps the ridge at bay. The latest GFS/Canadian 
tell a slightly different tale and both plow the frontal boundary 
(likely driven southward by convective outflow) through the area 
on Tuesday afternoon and evening with pockets of convection 
accompanying the boundary. With triple digit heat, high cloud 
bases and steep low level lapse rates, this would certainly cause 
some concern for strong storm outflows. Moreover, these solutions 
keep most of Wednesday and beyond precip-free as they build the 
ridge much quicker. What does appear consistent in all models is 
the presence of a diffuse back-door front that will slide eastward
and stall near the I-35 corridor by late Thursday. 

For the official forecast, I'm not confident that the areal 
coverage of convection forecast to develop upstream across 
Kansas/Oklahoma will be enough to surge any front southward into
North Texas as suggested by the Canadian/GFS. Hi-res NWP should 
be able to tell a more complete story as we get into early next 
week regarding this. With that in mind, I've sided with the first
portion of the 12 UTC Friday/00 UTC Saturday ECMWF for a slightly
slower FROPA and delayed CI Tuesday evening into Wednesday 
morning. This means low rain/storm chances for the eastern two- 
thirds of the FA through at least Thursday. I believe it's 
unlikely that we will see widespread convective development as far
west as the Big Country (per the ECMWF) on Thursday and believe 
that the ridge will build back to the east faster (per the GFS).
Thus I'll only keep a low chance for showers/storms near and east
of I-35 where there could be some slight ascent along the decaying
surface frontal boundary. 

Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth   101  81 102  82 102 /   0   0   0   0   0 
Waco               102  79 101  79 103 /   0   0   0   0   0 
Paris               97  76  99  78 101 /  20   0   0   0   0 
Denton             101  80 101  81 103 /   0   0   0   0   0 
McKinney           100  80 100  80 101 /   5   0   0   0   0 
Dallas             102  83 102  83 102 /   0   0   0   0   0 
Terrell            102  80 101  79 100 /   5   0   0   0   0 
Corsicana           97  78 100  78 101 /   0   0   0   0   0 
Temple             101  77 100  77 103 /   0   0   0   0   0 
Mineral Wells      102  78 102  78 105 /   0   0   0   0   0 

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT Sunday for TXZ091>095-100>107-
115>123-129>135-141>148-156>162-174-175.

&&

$$

05/24