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

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FXUS64 KFWD 240915

Area Forecast Discussion
National Weather Service Fort Worth TX
415 AM CDT Mon Apr 24 2017

Quiet and very warm conditions are forecast over the next couple
of days with little to no precipitation expected. Warm conditions
are expected again on Wednesday with a low rain chances, mainly
across the eastern third of North and Central TX as a cold front
slides through the area. The cold front will usher in cooler and
breezier conditions with most areas near and west of I-35 remaining
precipitation-free in its wake. Southerly warm and moist flow at
the surface will intensify through the latter half of the week and
into the weekend. While low level humidity will increase,
southwesterly winds aloft will ensure a stout cap is in place
which will limit the areal extent of precipitation chances.
Current thinking is that the best chances for a higher coverage of
showers and storms won`t occur until the weekend.

Monday and Tuesday should be precipitation-free, despite the
sharpening of the dryline out across western zones. While this
boundary will be present, southwesterly flow aloft will result in
the development of a formidable cap remain in place. If a
convection can breach and maintain itself, the storm will have the
potential to become severe. This scenario appears highly unlikely
at this time. Monday will be mostly sunny with a few passing high
clouds, especialy across southern zones. Temperatures will climb
into the upper 70s to mid 80s on Monday afternoon. The dryline
will become more well defined on Tuesday and should slowly
progress towards the I-35 corridor. In the wake of the dryline,
southwesterly winds should promote downslope warming and allow
temperatures to climb to above normal levels with readings in the
mid 90s. To the east, high temperatures are also expected to be
above normal with many areas in the mid to upper 80s. If the
dryline mixes a bit further to the east, it`s possible that some
locations along the I-35 corridor may near or break record high
temperatures. There may be an low-end fire weather threat across
areas west of I-35 as forecast soundings are indicative of a
classic dryline passage with steep lapse rates and unidirectional
wind shear. Both of these factor will likely foster some momentum
transfer and breezy southwesterly winds. Overall, live vegetation
and generally poor energy release component`s (ERCs) should
mitigate a more appreciable fire weather threat. That being said,
the breezy conditions may support fire spread and a low-end grassfire
danger statement may be warranted on Tuesday. The dryline should
mix back towards the east during the overnight hours into
Wednesday morning, as moisture sloshes back up along the higher
terrain back towards the west as a low level jet of around 35-40
knots develops.

On Wednesday morning, there could be some streamer showers across
far eastern zones, but model guidance seems to frequently over do
the amount of precipitation. For now, will show a 15-20 PoP out
across eastern zones where low level moisture is expected to be
most abundant and we could see the development of a few light
returns beneath the strong temperature inversion. Models are in
fair agreement with the synoptic pattern regarding Wednesday`s
rain potential. An upper trough should dive south and eastward out
of the 4-Corner`s region. As this occurs, low level moisture
should lift northward quickly out of the Gulf of Mexico. The
quality of moisture should be somewhat poor given the recent cold
front intrusion and the return flow in most guidance appears to be
overdone, with the GFS being the most aggressive. The
ECMWF/CONSMOS output appear to be the most reasonable, so will
trend dewpoints and PoP chances towards these solutions. That in
mind, a sharp dryline should still progress towards the east with
a fast moving cold front diving southward out of Oklahoma. There
is some discrepancies between timing of FROPA with the 00 uTC NAM
being the fast outlier as opposed to the 00 UTC GFS/00 UTC ECMWF
solution. The 18 UTC TTU-WRF seems to be more in line with the
GFS/ECMWF and given the higher resolution of this model, went more
in line with the GFS/ECMWF /TTU-WRF consensus. Forecast soundings
indicate that a strong cap will be in place until the late
afternoon hours and thus, the front should pass through the
western 2/3rds of the forecast area without much fanfare (outside
of some breezy conditions). The one area that we will need to
monitor for possible convective development will be along the
front/dryline interface up along the Red River. Interestingly
enough, model output remains scant on precip chances here, but we
will have to monitor trends as in there could be sufficient mesoscale
ascent here for some convection. Farther to the east, the front
will pass through at a time in which the cap should begin to
weaken courtesy of daytime heating and large scale ascent as 70 to
80 meter heights overspread the area.

While this is a pretty potent upper trough forecast to move
through on Wednesday, there`s too much uncertainty with the depth
and quality of the moisture to warrant anything higher than a
30-40% PoP. The strongest synoptic scale forcing for ascent (and
thus rain chances) is expected across northeastern and eastern
zones. Instability and shear parameters do support a conditional
risk (conditional if storms develop) for strong to severe
thunderstorms with the main risks being large hail given the steep
lapse rates and strong/damaging thunderstorm wind gusts given the
likely high based nature of convection and amount of mid-level
dry air. The tornado risk looks to be limited as low level winds
will veer slightly. The gradual upscale growth into more of a
linear complex should also limit the tornado potential.

In the wake of the front, lower temperatures and breezy
conditions are expected as 12mb/6 hr surface pressure rises
overspread areas north of the I-20 corridor. Temperatures will
fall down into the 70s and 80s with dry low level air spilling
southward. This dry air will likely seep all the way down to the
TX Gulf Coast which will have important ramifications for
Thursday`s precipitation chances. Winds will shift back towards
the east and southeast quickly on Thursday as the next upper
trough develops out towards the west. Initially, models advertised
that the cold front would stall out across portions of Central
TX, but recent runs, which have a deeper trough, now push the
front as far south as the upper TX coast. Given the amount of dry
air forecast to spill southward in the wake of the front, it
appears unlikely that sufficient moisture will lift back towards
the north in time for appreciable rain chances on Thursday. As a
result, I`ll show a dry forecast for all of the area through
Thursday. Low level moisture will return quickly on Friday ahead
of the next upper trough.

As expected, models have slowed the eastward progression of the
upper trough as it should continue to dig southward through
Arizona and New Mexico. The warm front will lift northward, and
while there may be some ascent atop the frontal surface, it
appears that the best focus will be to the north of the Red River
late Thursday into Friday. With strong capping expected per
forecast soundings and little in the way of forcing across North
and Central TX, rain chances should generally be below 20
percent, mainly along the Red River zones. Late Friday afternoon,
the dryline does appear to sharpen somewhat, beneath the
southwest flow aloft. While there is the potential that a subtle
wave could ripple through, it appears pretty unlikely at this time
and so for now, will show a 10-15 PoP mainly out across western
zones and along the Red River. If a storm can develop, it`s
probable that they will be strong to severe as shear and
instability parameters will support supercellular storm
structures. At this time, it`s too early to tell whether or not
enough forcing for ascent will be in place to breach the cap
across North TX, so for now, stay tuned for updates.

The long term forecast remains challenging and diverse model
solutions result in low confidence in timing and placement of
PoPs. As a result, significant alterations were not made to this
portion of the forecast from the previous issuance. Saturday and
into Sunday at this time appear to be the better chances for more
widespread showers and thunderstorms. Given the forecast shear and
instability profiles a few of these thunderstorms could be strong
to severe. The 00 UTC ECMWF appears a bit more progressive with
the upper trough and slice the dryline quickly through North and
Central TX through the day on Saturday. The 00 UTC GFS and to
some extent, the 00 UTC Canadian are a tad slower and keep the
dryline back towards the west before advancing it eastward through
the day on Sunday. At this time, am inclined to lean more on the
GFS/Canadian solution given model trends and the greater
likelihood that the upper trough will continue to dig southward,
thus slowing its eastward progression. With that being said, I
broad-brushed PoPs with values in the 20-40% range given the
uncertainty in timing on Saturday and Sunday. We`ll have to watch
the weekend carefully as robust values of instability and shear
could mean the potential for a severe weather episode across the



/ISSUED 1136 PM CDT Sun Apr 23 2017/
Surface high pressure is cresting overhead at this hour resulting
in light and variable winds, which will become south-
southeasterly overnight. No aviation concerns are anticipated
through the forecast period, and VFR will prevail with passing
high clouds on Monday. A southerly breeze will persist Monday
night as an area of low pressure passes well to our north.



Dallas-Ft. Worth    80  62  89  67  77 /   0   0  10  10  10
Waco                80  59  88  70  85 /   5   5  10  10  10
Paris               78  56  83  65  72 /   0   0  10  20  40
Denton              79  58  89  64  74 /   0   0  10  10  10
McKinney            79  59  85  66  75 /   0   0  10  10  20
Dallas              80  63  87  68  79 /   0   0  10  10  10
Terrell             79  59  85  67  78 /   0   0  10  10  30
Corsicana           80  59  86  68  84 /   0   0  10  10  30
Temple              80  60  87  70  88 /   5   5  10  10  10
Mineral Wells       82  58  94  63  76 /   5   5   5  10   5




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