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Area Forecast Discussion (AFD)

Issued by Brownsville/Rio Grande Valley, TX (BRO)

                            
000
FXUS64 KBRO 161142 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
642 AM CDT Tue Oct 16 2018

...12z Aviation Update...

.DISCUSSION...Updated for latest aviation discussion below.

&&

.AVIATION...MVFR conditions expected through today. Terminals will
flirt with IFR from time to time as well. Kept IFR this morning
with a gradual improvement. We'll go back to IFR around or shortly
after sunset this evening. Guidance is also suggesting we'll be
back to MVFR by 09z at all TAF sites prior to the end of the
cycle. Did reflect this in the forecast, but confidence is low to
moderate at the moment. Otherwise, light showers and drizzle
expected through the cycle. At this point, rather uncertain in
timing and placement of the pockets of drizzle and light rain. To
compensate for the uncertainty kept VC's, however, did at a PROP 
group beyond 09z for drizzle for all sites. Finally, strong 
northerly winds will continue. Pilots can expect a not so subtle 
wind shift at around 2kft or so with the interaction of the 
frontal boundary aloft.


&&

.PREV DISCUSSION... /issued 353 AM CDT Tue Oct 16 2018/ 

SHORT TERM (Today through Wednesday):The southward surging cold 
frontal boundary that pushed through the region on Monday sits off 
the TX/MX coastline this morning. Cold air is still advecting, 
however, doubt we'll drop much between now and sunrise. The drop 
behind the front was rather impressive with temperatures dropping in 
some cases close to 40 degrees (from around 90F to lower 50s in just 
a couple of hours). 

With the front offshore, a surface coastal trough is still projected 
to develop all along the TX coastline. This coastal trough will 
persist through the entire short term period. With the trough expect 
cool, blustery, and damp conditions across the region. With plenty 
of isentropic upglide with the front residing just downstream, 
expect overcast skies. At this point, model guidance is struggling 
with precipitation just a bit. With the initial frontal passage most 
models were fairly bullish, however, activity was more scattered 
than initially thought. That said, models are still not helping 
pinpoint specific timing rainfall will occur. With at least some 
modest QPF pinging in the globals, kept POPs mostly unchanged minus 
a few adjustments to fit our neighboring office. Think whatever 
precipitation falls in the short term should be on the light side. 
In many cases, it could be nothing more than light pockets of 
drizzle around. 

As for temperatures, expect high temps to remain well below the 
average high (usually in the middle 80s) with many locations not 
getting out of the 50s today and perhaps 60s on Wednesday. 

LONG TERM (Wednesday Night through Monday):The stagnant wet and 
relatively cool weather pattern to be maintained through the long 
term with models remaining in good consistency and fair 
agreement. The day to day details are difficult to decipher 
(especially as we go farther out in time) but the overall above 
normal chances of rainfall and below normal temperatures remain 
within the general trend.

Mid level low over the Desert Southwest and ridging across the Gulf 
of Mexico continue drive a very moist south-southwest mid-upper flow 
over Mexico into S Texas from the Tropical Pacific and the Southern 
Gulf. While mid/upper level ridge over the Pacific NW and over the 
Midwest/East will maintain surface high pressure over and to our 
north through with additional reinforcing high pressure next 
weekend. Also at the surface, the stalled front and coastal trough 
off the Lower Texas coast will continue to be the staging point for 
day to day rain with occasional bouts of convection.  Models remain 
consistent showing higher chances of rain Wednesday night/Thursday 
and again next weekend especially near the coast as the front and 
coastal trough fluctuates west to east and encounters disturbances, 
within the southerly flow, and influxes of anomalous tropical 
moisture (Pwats 2-2.4 in).  Nuisance flooding remains a viable 
threat across the Eastern counties with 7 day WPC QFP values still 
averaging 3-5 inches in the east and 2-3 inches in the West.  A 
Flash flood watch is still a possibility for the initial surge Wed 
night and Thursday but will wait another model run before 
considering.  

The relatively cool airmass over the region will already be under 
some modification and model guidance continues to indicate a steady 
warming trend. Similar to the the previous forecast will show slower 
warming due to the continued thick overcast and high rain chances. 
Coastal and Eastern counties are likely to see better warming if the 
coastal trough inches closer to the coast line. Re-enforcing high 
pressure moves in behind another front, that moves farther east then 
south next weekend, however cooling remains limited at this time. 

MARINE:(Today through Wednesday): Adverse marine conditions are 
ongoing across the adjacent gulf waters and the Laguna Madre. At 
Buoy 42020 winds have been gusting to near 30kts with wave heights 
as high at 7 feet at times. Hazardous marine conditions are expected 
to continue through the short term period and again perhaps beyond. 
Wave heights will likely begin to respond more later today and 
especially tonight as surface winds begin to veer to a more 
northerly or perhaps even a little east of due north direction. 

Wednesday night through Saturday...The continued presence of high
pressure over Texas and a stalled front and coastal trough off 
the lower Texas coast will maintain unsettled hazardous marine 
conditions. Gradient remains tight Wednesday with strong 
northwest-north winds and rough seas persisting. The coastal 
trough edges west approaching or even moving over the coastal 
waters Thursday and Friday with the pressure gradient relaxing. 
However seas will be slow in subsiding due to overall easterly 
flow over the much of the Gulf of Mexico. Surface high pressure 
rebuilds in next weekend and the wind gradient once again 
strengthens. Small Craft advisories are likely to be extended for 
much of the week. 

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 7 AM CDT Wednesday for GMZ130-132-135-
     150-155-170-175.

&&

$$

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Short Term/Aviation...Frye-55
Long Term/RDA...59