083 
fxus64 kcrp 201558 aaa 
afdcrp 


Area forecast discussion...updated 
National Weather Service Corpus Christi Texas 
1058 am CDT Wednesday Aug 20 2008 


Discussion...morning soundings show high moisture and 2 inch+ precipitable waters  
holing onto the coastal plains and offshore areas. 12z NAM has 
come in very dry and this appears to be overdone. Continue to like 
GFS/ecm depiction of a moisture axis (h85 Theta-E ridge) over the 
eastern half. Strong heating with highs near 90 east and into the 90s 
west with high dewpoints will lead to very high instability this 
afternoon west/ convective available potential energy possibly around 3000-4000 j/kg while weak winds 
provide a distict sea breeze boundary very active west/ thunderstorms this 
afternoon. Based on radar...lowered probability of precipitation for remainder of the morning 
most areas...but have kept 40-60 probability of precipitation for the coastal plains and 
Gulf waters...with 20-30 probability of precipitation far west where more dry air has 
crept in. High convective available potential energy point to possibility of a few stronger storms 
with gusty winds and locally heavy downpours. Some isolated 2-3 
inch rainfall totals are possible but appears any heavy rainf/flood 
threat is to localized for a Flash Flood Watch. 


&& 


Previous discussion... /issued 726 am CDT Wednesday Aug 20 2008/ 


Discussion...since convection continuing over the northwestern 
County warning forecast area with sufficient quantitative precipitation forecast...updated zones for this. Fog also put in 
(thought it was in there before). No other changes. Sorry for the 
delay in aviation discussion below as other issues to attend to 
this am. 


Aviation...pretty much maintained tempos for precipitation for eastern 3 
tafs today as expect convection to be not as widespread. 
Again...thunder in late morning through middle afternoon then should be 
over with. VFR conditions expected after 15z all areas except 
invoc of showers/thunder today. Will likely see some MVFR 
conditions in ceilings and/or visibilities all tafs at or above 09z Thursday am. 


Previous discussion... /issued 333 am CDT Wednesday Aug 20 2008/ 


Short term (today through thursday)...main question early part of 
this package is convection over The Hill Country...how far south 
will it go and how strong/heavy will the rainfall be if and when 
it gets into northern County warning forecast area. Believe convection will get into 
northeastern counties later this morning...as convection is being 
fed with moderate 850mb Theta-E air and very weak warm air 
advection. However 850mb - 300mb thickness pattern show storms 
will begin to move more to the east...then northeast and with 
little storm inflow and storms going into warmer middle levels and 
more cap still some uncertainty. At this time...expected activity 
to mainly effect northeastern sections (victoria...Goliad and 
maybe bee). Elsewhere...models generally indicate that main 
convective activity will be over the eastern areas today where 
Theta-E advection and best moisture reside...as well as area being 
east or at least closest to the 700mb trough so highest probability of precipitation there 
with slight chance far west. As we have seen over the past couple of 
days...should see a lull in the action in the evening and 
overnight hours. Models then increase moisture over the area (gfs 
near 2.4 inches) on Thursday and GFS/NAM show 700mb- 300mb q-vector 
convergence and possibly an approaching jet with 850mb Theta-E 
ridge feeding area. Thus...will increase probability of precipitation a bit from previous 
forecast but not go with the highest guidance just yet as am not 
sure if upper low and middle trough may be east of area and thus we 
will remain on the wrong side. High temperatures east should remain 
below normal (a bit higher today and Thursday...though a bit 
higher today with slightly less areal coverage in rain. Minimum 
temperatures should be near normal and close to guidance values. 


Long term (thursday night through tuesday)...the first part of the 
extended begins with an upper level trough axis west of the region 
with south Texas on the favorable side for convection. In 
addition...the latest GFS and European model (ecmwf) forecast a middle-level circulation to 
develop over deep south Texas Thursday night and move north along 
the Rio Grande Friday. This feature is expected to enhance the upper 
support already over the region. As a result...decided to kick up 
probability of precipitation Friday afternoon given those two features in place combining 
with ample moisture/instability. Models continue to struggle with 
run to run consistency based on the evolution of the middle-level 
circulation and subsequent moisture fields. The latest European model (ecmwf) lifts 
the circulation into the I-10 corridor Saturday and absorbs it into 
T.S. Fay Sunday into Monday as the tropical storm churns into the 
northern Gulf. This solution would dry out the region Sunday through 
Tuesday. On the other hand...the GFS retrogrades/elongates the 
circulation into West Texas and keeps south Texas in a favorable 
environment for convection through the rest of the period. The 
latter solution does not seem feasible and therefore am not buying 
the GFS solution. As a result...decided to undercut mexmos guidance 
probability of precipitation for the weekend into the first part of next week. Still think 
sea breeze convection will exist through the weekend...but should 
start to taper off early next week as T.S. Fay scours out the 
moisture across south Texas. As far as temperatures are concerned...will 
maintain the current below normal maximum temperature forecast due to saturated 
soils and near normal min temperatures. 


Marine (today through thursday)...weak to moderate onshore flow 
outside of convection...with winds and seas higher in and near 
scattered to numerous showers/storms through period. 


&& 


Preliminary point temps/pops... 
Corpus Christi 90 75 91 77 90 / 50 20 50 20 50 
Victoria 89 74 89 75 91 / 60 20 50 20 50 
Laredo 97 78 97 78 97 / 20 10 20 20 30 
Alice 93 74 93 76 92 / 50 20 50 20 50 
Rockport 89 78 89 78 89 / 50 30 50 20 40 
Cotulla 95 75 96 75 95 / 20 10 20 20 30 
Kingsville 91 75 92 77 91 / 50 20 50 20 50 
Navy corpus 88 78 89 79 89 / 50 20 50 20 40 


&& 


Crp watches/warnings/advisories... 
Texas...none. 
GM...none. 


&& 


$$ 


Mjg...update 

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