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Area forecast discussion...updated 
National Weather Service Fort Worth Texas 
633 PM CST Sat Nov 7 2009 


Aviation... 
expect another surge of low level moisture to spread northward 
overnight. Have forecasted IFR ceilings into Waco by 08z...and 
into the metroplex by 10z. Ceilings will improve to MVFR 
15-17z....and to VFR after 18z in the metroplex...and 21z at 
Waco. Rain chances Sunday afternoon and night are too low to 
mention at this time. South to southeast winds of 8 to 12 knots 
will prevail. 


58 


&& 




Previous discussion... /issued 353 PM CST Sat Nov 7 2009/ 


Primary forecast concern is the precipitation chances associated 
with the shortwave trough just south of nm and Arizona at forecast 
time. 12z models all kick the shortwave trough out northeast over 
the next 24 hours spreading large scale forcing for ascent over 
North Texas beginning late tomorrow morning and extending through 
about midnight Sunday night. 20z water vapor imagery and upper level 
pv analysis indicate the presence of a cyclonic shear axis 
associated with the subtropical jet extending through the southern 
Baja California peninsula and into Mexico. Models seem to point to this 
feature as being at least partially responsible for developing a 
convective complex over the Gomex during the overnight hours. This 
area of persistent convection is expected to cause a surface 
low/inverted trough to deepen near the Texas/la coast backing the low 
level winds along the Gulf Coast...effectively limiting the 
potential moisture transport of deeper Gulf moisture into North Texas 
for Sunday. 12z models have also been shearing out the upper level 
pv anomaly as it moves northeast towards the County Warning Area here starting 12z 
Sunday. Despite the potential for a weaker upper level shortwave 
trough forcing for ascent is expected to remain strong over North 
Texas ahead of this wave...so have kept low chance probability of precipitation in the 
forecast for Sunday. The areas expected to see the deepest Gulf 
moisture return in the County Warning Area are those areas generally south of the 
Waco area. Areas in North Texas that receive the best Gulf moisture 
are most likely to see some embedded thunderstorms within the 
general scattered rain shower activity that is expected to develop 
in the broad forcing for ascent associated with the shortwave 
trough. As the trough departs off to the northeast after sunrise 
on Monday...any lingering precipitation should quickly diminish as 
large scale forcing for subsidence spreads over the region. 


Monday through Tuesday...the cold/Pacific front still looks on 
track to move southeast through North Texas Monday night. 12z model 
runs are now bringing some upper level support along the frontal 
boundary in the form of a weak shortwave trough pushing southeast 
through OK and the Red River Monday night through Tuesday morning. 
Because of the upper level support...introduced slight chance for 
rain showers for areas generally along and north of Interstate 20 
with the frontal boundary and upper level support looking to move 
through the area. Did not spread probability of precipitation further south as forcing 
along the front by itself does not look strong enough to support 
precipitation at this time. Behind the front...skies should begin 
to clear out for Tuesday afternoon as upper level ridging builds 
back over the Southern Plains. 


Wednesday through Friday...in general upper level ridging looks to 
hold over the forecast area allowing for a dry forecast. The upper 
flow looks to transition to southwest as a broad upper level trough 
moves into the western Continental U.S.. this will bring fairly strong Lee 
side troughing over the High Plains bringing a period of 
persistent southerly flow through Texas...allowing for some deeper Gulf 
moisture return by Friday. 


Friday night and Saturday...upper level energy looks to remain north 
of the forecast area...however a strong shortwave trough moving 
through the plains should send a cold front southeast into North Texas. 
With better moisture in place kept precipitation chances across the 
forecast area along the cold front even without significant upper 
level forcing for ascent over the area. 


Cavanaugh 


&& 






Preliminary point temps/pops... 
Dallas-ft. Worth, Texas 59 75 58 76 54 / 5 20 30 10 20 
Waco, Texas 59 76 56 76 53 / 5 40 30 10 10 
Paris, Texas 53 74 54 75 53 / 5 20 30 10 20 
Denton, Texas 56 74 55 75 52 / 5 20 30 10 20 
McKinney, Texas 55 74 58 75 53 / 5 20 30 10 20 
Dallas, Texas 61 75 58 76 55 / 5 20 30 10 20 
Terrell, Texas 56 75 58 76 54 / 5 20 30 10 20 
Corsicana, Texas 59 77 57 76 54 / 5 30 30 10 10 
Temple, Texas 58 76 58 76 53 / 5 40 30 10 10 


&& 


Forward watches/warnings/advisories... 
none. 


&& 


$$ 


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