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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Sunday
• 
• High: 88 °
• Low: 68 °
• Chance of a Thunderstorm

• Monday
• 
• High: 91 °
• Low: 73 °
• Chance of a Thunderstorm

• Tuesday
• 
• High: 86 °
• Low: 64 °
• Chance of T-Storms

• Wednesday
• 
• High: 84 °
• Low: 64 °
• Chance of Rain

• Thursday
• 
• High: 88 °
• Low: 70 °
• Clear

Area forecast discussion 
National Weather Service Fort Worth Texas 
705 PM CDT Sat may 18 2013 


Aviation... 


For the 00z tafs...timing the onset of stratus...and the impact of 
any anvil cloud precipitation over metroplex area taf sites are 
the primary forecast concerns. 


Regarding stratus...kept MVFR stratus in the forecast for a few 
hours tomorrow morning as most guidance agrees that a 50 knots low 
level jet will ramp up over North Texas tonight. This strong jet will 
help keep Gulf moisture in place...but there is uncertainty 
regarding the presence of stratus within the low level jet. The 
low level jet is not expected to be associated with strong warm 
air advection overnight...therefore there will only be shallow 
lift within the core of the jet over North Texas. This shallow lift 
may be sufficient for stratus to form...but there is no guarantee 
that this will pan out. The lamp is aggressive with the stratus as 
it has been recently. The rap forecast soundings do not support 
the development of stratus while the NAM does. At this point just 
kept the stratus in the forecast but bumped up the ceilings to 2500 feet 
which should have little impact on Airport operations even if it 
is in place. 


Regarding anvil cloud precipitation tonight...placed a mention of 
light rain with gusty winds in the forecast from 06 to 09z for 
metroplex area taf sites. This will only occur if storms become 
established around Abilene this evening. At the time of this 
discussion visible satellite and regional radar showed some good 
convective attempts just north of Abilene...and this tipped the 
scale towards including the light anvil precipitation in metroplex 
area tafs. Any light rain in the extremely unstable air mass in 
place over North Texas will result in heat bursts...or heat burst like 
activity. Essentially very gusty winds accompanied by a warming 
and drying out of the near surface air. If the Abilene activity 
never becomes established...will remove this group from the tafs 
in future amendments. 


Cavanaugh 


&& 




Previous discussion... /issued 324 PM CDT Sat may 18 2013/ 
a slow moving upper level trough over the plains will put the 
region in an active weather pattern through Tuesday with severe 
weather possible each day. Primarily the northwest/northern parts 
of the County Warning Area will be impacted by convection tonight through 
Monday...but the central and southern County Warning Area will be under the gun 
for a widespread rain event Tuesday afternoon and evening. The 
main change with this forecast concerns tonight...and the addition 
of probability of precipitation for areas north of I-20...not necessarily for supercell 
type convection...but for very high based weak convection that 
could cause strong gusty winds via heatbursts late this evening. 


This afternoon the dry line remains well to the west of the region 
and short-term guidance suggests it will stay as far west as a 
Childress to San Angelo line. This results in some concerns about 
whether surface based convection will initiate close enough to 
enter the County Warning Area. Middle level westerly flow is stronger today...and 
therefore storm motions would be more easterly. Surface based 
convection would have enough shear and instability to become 
supercells and produce significant severe weather. Local objective 
analysis indicates the best axis of instability and diminished cin 
is to the west of the County Warning Area...with the airmass over our western 
counties not quite as unstable with cape at 1500-2500 j/kg and 
higher cin due to dewpoints dropping into the low 60s. Water vapor 
loop and model guidance does indicate a shortwave is approaching 
from the southwest and the lift provided by this feature should 
allow surface based convection to initiate and organize west of 
the County Warning Area. Some of this activity should enter the northwest zones...but 
believe the cells may weaken a bit and become elevated due to the 
slightly less favorable environment. In summary...a severe threat 
exist for primarily hail/wind...and probability of precipitation are near 20-30 percent in 
the northwest zones early this evening. The risk for giant hail or 
tornadoes does not look as high as it did yesterday in our County Warning Area. 


Currently...weak elevated convection based at around 14000ft 
continues to bubble up over the western zones. Most of the precipitation 
is evaporating before reaching the ground...but this elevated 
moisture plume looks like it will have implications on the forecast 
over the northern half of the area tonight. Essentially there are 
a few models now indicating a moisture plume from 500-600mb 
entering the northern half of the area...likely associated with 
anvils from storms to the west. The issue is that this moisture 
will be within an area of dry adiabatic lapse rates...and 
coincides with upper level forcing from the shortwave. The stage 
is set for scattered elevated convection with bases above 12000ft. 
Most of the rain will evaporate due to very dry air below 600mb... 
but sporadic lightning strikes will be possible tonight. 
Meanwhile...a 50kt southerly low level jet will be developing and 
the environment will be favorable for this high based convection 
to Transfer strong winds to the surface in what is technically a 
type of heatburst. This is tough to communicate to the public in 
simple terms...but the probability of precipitation are for measurable rain and the chance 
for that is low. However gusty winds and light rain may affect a 
large portion of the northern County Warning Area tonight...and therefore have 
bumped up south winds to 20-25 miles per hour and mentioned gusts to 40 miles per hour 
in the zones. This forecast is not of high confidence...partly 
because it may be The First National Weather Service forecast that has ever tried to 
include a risk of heatbursts in a zone forecast. However looking 
at all of the data...the setup tonight looks very favorable for 
period of gusty south winds beneath elevated radar echoes. We 
shall see. 


A strong shortwave trough will rotate through the Southern Plains 
tomorrow and will push the dryline farther to the east into the northwest 
zones. With daytime heating...cin should be low enough over the northwest 
zones for isolated severe storms to develop in the afternoon. 
Wind fields will strengthen a bit and supercell storm motion will 
be easterly. West to east storm tracks on Sunday evening means 
probability of precipitation will cover the areas north of I-20. Low level helicity ramps 
up around sunset Sunday evening and if supercells can overcome the 
weak cin and tap into surface parcels...a tornado threat will 
exist. Monday looks like a Carbon copy of Sunday/S pattern with 
the main features in the same place...just a little weaker cin so 
probability of precipitation are slightly higher/farther south. Temperatures will remain near 
persistence and winds will be breezy Sunday and Monday. 


On Tuesday the upper trough will begin to finally move east and 
this will push a cold front into the northwest zones Tuesday afternoon. 
Scattered to numerous storms should fire along the cold front 
Tuesday afternoon and work east and southeast across much of the 
area into Tuesday night. Rainfall may be widespread and average 
1/2 to 1 inch. Severe weather will be a concern given high 
instability and adequate deep layer shear. 


The front will push through the region and drier air will end rain 
chances from north to south Wednesday. Low temperatures will cool a bit 
and into the 60s due to the lower dewpoints...but highs will 
continue in the middle 80s to near 90 through the remainder of the 
week. Will keep the forecast dry as an upper ridge settles into 
the area...but we may have to watch for northwest flow mesoscale convective system activity on 
Friday night in the northwest zones. Too far out to rely on the model 
forecasts for this possibility at this time. 


Tr.92 


&& 






Preliminary point temps/pops... 
Dallas-ft. Worth, Texas 73 90 72 89 72 / 20 10 20 10 20 
Waco, Texas 72 90 73 90 73 / 10 5 5 5 10 
Paris, Texas 70 88 70 87 70 / 20 10 20 10 40 
Denton, Texas 73 90 71 89 70 / 20 10 20 20 30 
McKinney, Texas 73 89 71 88 71 / 20 10 20 10 30 
Dallas, Texas 75 91 74 90 74 / 20 10 20 10 20 
Terrell, Texas 72 88 71 89 73 / 10 5 20 10 20 
Corsicana, Texas 71 89 72 89 73 / 10 5 5 5 10 
Temple, Texas 71 89 73 90 73 / 5 5 5 5 10 
Mineral Wells, Texas 71 93 70 92 71 / 20 20 20 20 20 


&& 


Forward watches/warnings/advisories... 
none. 


&& 


$$