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FXUS64 KFWD 251734

Area Forecast Discussion
National Weather Service Fort Worth TX
1134 AM CST Sat Feb 25 2017

VFR and clear skies will prevail through tonight as generally 
light winds veer from the north this afternoon, to the east this 
evening, and to the southeast by daybreak. 

Southerly low level winds will increase during the morning hours
Sunday and bring a rapid return of low level moisture. MVFR CIGS 
should arrive into Waco around 15z and the DFW Metroplex around 
17z and prevail through the day. Moisture and instability 
increases enough for a chance of showers by late in the afternoon 
and will include a VCSH in DFW extended TAF. Elevated instability
may be high enough Sunday night for scattered storms in the 
TRACON, but believe that the best potential for thunder will be 
east and southeast at this time.



.PREV DISCUSSION... /ISSUED 340 AM CST Sat Feb 25 2017/
We're off to a cold start this morning, especially across North 
TX where temperatures are expected to reach the freezing mark at
some rural outlying areas before sunrise. Winds have remained 
breezy overnight as a strong surface high continues to build 
southward through the Plains, but winds will begin decreasing 
later this morning as the high becomes centered over North TX. 
Much drier air continues to filter in with these northerly winds 
and dewpoints are expected to fall into the teens and 20s area- 
wide later today as mixing ensues. It will be a cool, but 
pleasant Saturday afternoon with highs in the 50s and low 60s.

Changes will begin on Sunday morning as broad troughing develops 
across the western US. A warm advection regime will be in place 
across the region from Sunday through Tuesday night which will 
supply North and Central TX with rich moisture, above normal 
temperatures, and multiple rain/storm chances including the 
potential for some strong or severe storms as disturbances pivot
through the parent longwave trough. Generally, the farther east 
in the forecast area, the greater the chance for storms during the
Sunday night through Tuesday night time frame.

The return of moisture and warmer air will begin tonight as winds
turn to the south and surface high pressure shifts east. A 40+ kt
LLJ will begin to advect in low-level moisture resulting in 
widespread cloudiness for much of Sunday. In addition, this 
momentum will mix down to the surface by late Sunday morning 
through the evening resulting in gusty south winds of 20-30 mph. 
During the afternoon hours, enough moisture will be available to 
generate showers within the axis of strongest warm advection; the
highest coverage of showers is expected roughly along and east of
I-35. Instability will begin increasing Sunday evening as lapse 
rates steepen due to an approaching shortwave trough. Showers and 
storms will be on the increase during this time with ample lift 
both from the shortwave trough and from very strong low-level warm

The passing shortwave will drag a weak front into the Southern 
Plains Sunday night with a surface low developing across the TX 
Panhandle. There are discrepancies among the models as
to how far south this front will reach, but it's possible that it
will stall somewhere in the vicinity of I-20 around daybreak. 
There will probably be a lull in thunderstorm activity Monday 
morning as weak subsidence follows behind the departing shortwave 
and warm advection lessens with the weakening of the low-level 
wind fields. South of the front, moisture will still be on the 
increase and fog will be possible; have not included a fog mention 
in the official forecast just yet as there is too much uncertainty
to delineate the most favorable area. 

Early Monday afternoon, a dryline will take shape near or slightly
west of I-35 associated with the aforementioned developing 
surface low and the stalled front will surge back north as a warm 
front. Dewpoints will have climbed into the low to mid 60s east of
the dryline which will result in SBCAPE of 1000-2000 J/kg across 
our eastern zones. While little in the way of dynamic forcing will
be available, there will still be isentropic ascent through the 
low levels and steep lapse rates in the 700-500mb layer. As a 
result, scattered storms should be capable of developing within 
the warm sector airmass ahead of the dryline and northward toward 
the warm front on Monday afternoon. With 50+ kts of deep layer 
shear in place, storms will have the potential to become strong to
severe as long as buoyancy is able to result in strong updrafts 
and overcome the lack of large-scale dynamic lift.

The dryline should stall before progressing very far east and 
will retreat westward overnight. Models have come into better  
agreement on a western solution for the dryline position on 
Tuesday, spreading a swath of mid 60s dewpoints across the eastern
2/3rds of the forecast area. In addition, temperatures will be 
well above normal with another "winter" 80-degree day possible. 
There should be more instability in place on Tuesday than on 
Monday as mid-level lapse rates drastically steepen as a second, 
more powerful shortwave sweeps through the Plains. Stronger 
isentropic ascent in addition to lift from the shortwave trough 
will be sufficient to generate scattered storms again Tuesday 
afternoon within the warm sector ahead of the dryline. SBCAPE of 
around 2000 J/kg could be present with over 60 kts of deep layer 
shear as a strong 500mb jet overspreads North TX. If these 
conditions materialize, some strong to severe storms will be 
likely on Tuesday afternoon.

Later Tuesday night and Wednesday morning, the strong shortwave
will be departing to the northeast while dragging a strong cold
front through the area. A few showers and a few storms will be 
possible along the front as it catches up the dryline's location,
but the strong/severe storm potential should be decreasing during 
this time. Much colder air and strong northwest winds will follow
this fast-moving front as it surges through the forecast area
Wednesday morning. Have undercut temperature guidance slightly 
for the Wednesday-Thursday time frame. Dry and cooler conditions 
should persist through the end of the week before low rain chances
resume next weekend.



Dallas-Ft. Worth    57  42  66  57  78 /   0   0  20  30  40 
Waco                59  41  67  58  77 /   0   5  30  40  30 
Paris               53  35  62  52  68 /   0   0  30  60  50 
Denton              54  38  65  54  75 /   0   0  20  30  30 
McKinney            57  37  63  54  74 /   0   0  30  40  40 
Dallas              57  42  67  58  78 /   0   0  30  40  40 
Terrell             55  39  65  57  74 /   0   0  40  50  40 
Corsicana           57  41  67  59  76 /   0   0  40  60  40 
Temple              59  40  68  58  77 /   0   5  30  40  30 
Mineral Wells       55  39  67  52  76 /   0   0  20  20  10 



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