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Area Forecast Discussion (AFD)

Issued by Fort Worth/Dallas, TX (FWD)

                            
919 
FXUS64 KFWD 221138 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
638 AM CDT Fri Jun 22 2018


.AVIATION...
/12Z TAFs/

VFR conditions are expected today with breezy winds. The winds are
currently out of the southwest but are expected to become more
westerly this morning in response to a front approaching the Red
River. The location of the front is muddled by a complex of storms
moving across western Oklahoma, and we will have to monitor its
location and progress for a possible wind shift at the DFW 
airports. The complex of storms is expected to weaken as it nears
North Texas, but cannot completely rule out some rain at the DFW
airports this morning. However, all of these possibilities are too
conditional to mention in the TAF at this time and will be closely
monitoring this morning.

This afternoon, the winds will come around to the south at around
15 kts with higher gusts. A few storms are possible this 
afternoon east of the airports which may impact traffic to and 
from that direction. Another complex of storms will form in the 
Texas Panhandle late today, but is expected to move in a more 
easterly direction across Oklahoma tonight, mostly staying north 
of the Red River. Some stratus clouds are possible around KACT 
Saturday morning.

JLDunn

&&


.SHORT TERM... /Issued 356 AM CDT Fri Jun 22 2018/
/Today and Tonight/

Hot but breezy conditions are expected across much of the region
today with a few showers and storms possible in our north and
northeast counties. A warm night is expected as a complex of
storms moves through Oklahoma and potentially grazes our northern
counties.

A front can be tracked on regional radars and surface observations
moving south through Central and Eastern Oklahoma early this
morning. A few showers and storms have developed ahead of the
front across Southeastern Oklahoma, and nighttime satellite is
showing a growing area of ACCUS expanding into our northern
counties. Most model guidance keeps these storms to our east and
northeast, but as the front continues to move south this morning 
we may see a few showers or storms in our northeastern counties.
Have maintained low PoPs through the morning hours along and
northeast of a Bowie to Sulphur Springs line as heating later this
morning may generate some elevated convection. The complex of 
storms that is taking shape in the TX Panhandle at this time is 
expected to weaken before reaching North Texas this morning but 
should spread high cloud cover into the region.

An upper level ridge will remain anchored to our west today and
tonight with northwest flow aloft continuing. The front should sag
into part of our CWA this morning but may not make it any farther
south than the northern row of counties. This front should be a
focus for convection this afternoon with the help of peak heating.
The instability this afternoon will be greatest in our northeastern
counties where CAPE values near 3500 J/kg are forecast in an 
uncapped environment. Deep layer wind shear values between 15-25 
kts and decent mid level lapse rates support a potential hail and 
damaging wind threat, but without a more significant mid-level 
shortwave, the forcing may not be strong enough to utilize this 
energy. We cannot discount a severe storm threat this afternoon 
but coverage of storms may be isolated at best. The area that may
see isolated to scattered storms this afternoon is roughly along 
and east of a line from Bonham to Athens.

Otherwise, today will be hot and breezy south of the front. A
plume of hot H850 temperatures is expected to spread across our 
western counties with the help of west to southwest winds this 
morning. Afternoon highs around 100 degrees will be common along 
and west of Interstate 35/35E with highs in the mid to upper 90s 
east of Interstate 35/35E. Even though they will be from the west-
southwest, 10-15 mph winds will provide some relief. Heat Index 
values across most of the region are calculated to remain below 
105 degrees, but some areas across Central Texas where the
humidity is higher will reach 105-107 degrees for a little bit
this afternoon. At this time, we do not plan to issue a Heat
Advisory as the breezy winds will likely reduce the heat stress 
factor, but that doesn't take away from the fact that dangerous 
heat conditions will occur today. In addition, slightly elevated
fire weather conditions may exist this afternoon west of Highway
281 where temperatures near 101 degrees, southwest winds 10-15 mph
and humidity values near 25 percent are expected.

Overnight, the winds will back to the south but remain breezy in 
response to a surface low moving southeast through the Texas
Panhandle. This surface low will be associated with a shortwave
trough moving through the Plains and is expected to foster the 
development of a MCS to our northwest. Steering flow winds move 
this system east across Oklahoma, but part of this system could at
least clip our northern row of counties along the Red River. The 
low level jet will increase to 35-40 kts overnight from the south 
and southwest, helping fuel this complex which could result in 
part of the system moving southeast towards our CWA. For now, will
maintain PoPs along and north of an Olney to Sulphur Springs 
line. Forecast soundings are in good agreement the region will 
remain capped tonight, but gusty winds may be possible, even if 
the storms remain elevated. Overnight lows will range from the 
mid 70s to around 80 degrees in the DFW Metroplex.

JLDunn

&&

.LONG TERM... /Issued 356 AM CDT Fri Jun 22 2018/
/Saturday through the End of Next Week/

The remnants of an MCS over Oklahoma may bring an area of
weakening convection to the Red River early Saturday, but activity
should dissipate by midday. Meanwhile, lee-cyclogenesis will be in
full swing as a shortwave drops southeast through the Great Basin.
The resulting increase in surface winds (which will have a more 
southerly component compared to Friday) combined with lingering 
cloudcover may keep temperatures a couple degrees below Friday's 
expected temps. It will still be a hot one, with highs ranging 
from the mid and upper 90s along and east of I-35 to triple digits
west. 

Zonal flow aloft will be in place Saturday with a lead disturbance
racing eastward across the Southern Plains in advance of the Great
Basin upper low. This should ignite another round of showers and 
storms in the vicinity of a stationary front, which will likely
remain draped somewhere near the Red River. An unstable
environment including a couple thousand J/KG of MUCAPE and mid
level lapse rates not all that far below dry adiabatic presents
the possibility of a few severe storms with any convection that
develops. The caveat may be that a decent capping inversion will
be in place, but a 40KT low level jet should help storms get going
above the cap.

The most likely location for severe storms would be along the Red
River Saturday evening with large hail initially being the 
primary threat, especially if any storms are able to rotate. Storm
mergers will eventually interrupt the rotation of any discrete 
cells, shifting the primary threat to damaging winds later in the 
evening. Activity should be in a weakening phase around or shortly
after midnight as convection approaches the I-20 corridor, the 
fast-moving wave exits to the east and subsidence from a ridge 
aloft becomes too strong to overcome.

Another hot one can be expected on Sunday, and the possibility of
a heat advisory comes to mind as the potential for heat indices to
reach or exceed 105 degrees for consecutive days will exist. The 
likely areas would be along the Trinity and Brazos River Basins 
where the hottest conditions will occur, which includes a good 
portion of the I-35 corridor. We will likely wait until later 
today or tonight to make the decision on whether or not to issue 
the advisory as changes in the evolution of tonight's and Saturday
night's convection may alter the temperature / heat index 
forecast.

The upper ridge aloft will break down a little late Sunday and 
Monday as the Great Basin shortwave trough crosses the Plains. A 
few storms associated with the trough will be possible on Monday, 
but with 500MB heights in excess of 590DAM and the presence of a 
good cap in place, will keep POPs in the slight chance category 
at this time. Mid range model data further strengthens the ridge 
from Tuesday on, meaning above-normal temperatures and dry weather
in the forecast for mid to late next week.

30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    99  79  99  79  98 /  10  10   5  20  10 
Waco               101  77  98  78  98 /   5   5   0   5   5 
Paris               93  75  93  75  94 /  30  30  20  30  20 
Denton              99  79  99  78  98 /  10  20  10  30  10 
McKinney            97  76  97  76  97 /  10  20  10  30  10 
Dallas             101  80  99  79  98 /  10  10   5  20  10 
Terrell             99  77  97  78  96 /  20  20   5  20  10 
Corsicana           98  76  97  76  95 /  10  10   0  10   5 
Temple              98  76  98  76  96 /   0   0   0   5   5 
Mineral Wells      101  78 102  77  99 /  10  10   5  20   5 

&&

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

$$

82/30