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Area forecast discussion 
National Weather Service Brownsville Texas 
217 PM CST Sat Nov 21 2009 


Discussion...a fairly progressive pattern will prevail across 
the lower 48 states for the upcoming forecast period as a steady 
series of 500 mb short waves continue to dig across the Continental U.S. 
Region from the west and northwest. A fairly zonal pattern will 
prevail over deep south Texas for the short term allowing fairly 
dry and benign conditions to prevail over the next couple of days. 
The current cool and dry surface high over the area will be 
steadily moving east allowing the low level flow to become more 
east-southeast resulting in an increase in surface dewpoints and warming 
temperatures. The next major middle level trough to affect the Rio Grande 
Valley area will dig into the Central Plains states late Monday 
cutting off Tuesday and Wednesday. This will push the next Midwest cold 
front through deep south Texas on Tuesday resulting in the next good 
rain chance for the region. After this front clears the region an 
eastern Pacific closed middle level Baja California low will form up and will 
move over the northern portions of Mexico during the latter half 
of the upcoming work week. Meanwhile at the low levels an east/NE 
flow will persist through the end of the week due to the surface 
ridging dominating the eastern half of the nation. This combination 
of west-SW flow aloft and the east-NE flow at the surface will likely 
maintain generous cloud cover during the latter half of this week. 
This Baja California low will eventually open up and will move over northeast 
mex and southern tex Friday and Sat with yet another broad 500 mb 
trough axis digging into the south Central Plains early next week. 
Will maintain a mention of some slight chance/chance probability of precipitation after Tuesday to 
account for this potential overrunning situation. Short term 
comparisons between the mav and met temperatures/probability of precipitation look pretty close 
and will not stray too far from this overall trend. Run to run and 
model to model consistency with long range guidance looks above 
average and will go close to mex probability of precipitation from days 3 to 7 and near to 
a little below guidance for maximum and min temperatures in the longer range. 
&& 


Aviation...mostly clear skies and light to moderate northerly winds 
are prevailing today across deep south Texas. Some higher cirrus clouds are 
advecting northward from Mexico and will drift overhead through this afternoon 
with no impacts to aviation interests. Fairly light north to 
northeast winds are expected to prevail through the overnight as high 
pressure takes control. Anticipate VFR conditions to persist through 
the next 24 hours. 
&& 


Marine...the 1 PM observation from buoy020 indicates winds were 
west northwest around 16 kts gusting to around 19 kts and seas were 
around 6 feet with a period of 8 seconds. Marine conditions will 
continue to gradually improve through this afternoon across the offshore 
waters. The day began with Small Craft Advisory conditions due to elevated winds and 
seas. High pressure will gradually take hold the rest of today through 
Monday. Marine SC clouds will gradually erode to the east-southeast through this 
aftn/eve. The light to moderate northerly flow will prevail into 
tonight. Winds will veer NE to east overnight through Sun night and remain light 
to moderate. Southeast flow will return on Monday as high pressure shifts 
farther east. Seas will continue to subside this afternoon and are 
expected to remain relatively low sun into Monday. The onshore southeast flow 
will begin to strengthen by late Monday into Tuesday in response to a cold 
front working through north and central Texas. Seas will gradually build 
possibly resulting in scec to possibly marginal Small Craft Advisory conditions. The 
front is prognosticated to push through the coastal waters on Tuesday. Small Craft Advisory 
conditions will be possible in conjunction with the frontal passage and 
possibly persist through Wednesday. 
&& 


Preliminary point temps/pops... 
Bayview/Port Isabel 57 77 65 80 / 0 0 10 20 
Brownsville 53 79 64 80 / 0 0 10 20 
Harlingen 52 78 63 82 / 0 0 10 20 
McAllen 53 81 62 83 / 0 0 10 20 
Rio Grande City 53 81 60 82 / 0 0 10 20 
South Padre Island 59 76 64 79 / 0 0 10 20 
&& 


Bro watches/warnings/advisories...none. 
&& 


$$ 


This product is also available on the web at: 
http://www.Weather.Gov/Brownsville 


Synoptic/grids...60 
marine/aviation...57 
mesoscale...Martinez