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Area Forecast Discussion (AFD)

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

FXUS64 KBRO 191738 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1138 AM CST Sat Jan 19 2019

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


.AVIATION...Mostly clear skies and breezy northwest winds prevail
across deep south Texas late this morning. The main impact for 
this TAF cycle will be the gusty northwest to north winds this
afternoon as some gusts may reach 30 knots at times. Winds
gradually diminish to around 10 knots by late evening as surface
high pressure builds into the region. VFR conditions will persist
for the next 24 hours. 


.PREV DISCUSSION... /issued 618 AM CST Sat Jan 19 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Brief low ceilings now, just under 1000 ft, as a cold
front rushes through the lower Valley. However, quick clearing 
will occur within a couple of hours. Then VFR but windy. Northwest
winds will be 20 to 30 mph and gusty today, with a few gusts to 
35 mph possible, most of the day. Winds will decrease this 
evening, however, becoming light overnight.

PREV DISCUSSION... /issued 443 AM CST Sat Jan 19 2019/ 

SHORT TERM (Today through Sunday):  A cold front is traversing 
the ranchlands and brush country of deep South Texas and the RGV, 
and should clear the coast in the next few hours. There is limited 
moisture ahead of the front and only isolated showers have been 
noted so far, but a rumble of thunder can't be ruled out along the 
leading edge of the boundary. Overnight temps have not decreased a 
whole lot and may be close to high temperatures for the day, 
depending on how much colder air gets into the area during the day. 
Not expecting temperatures to increase dramatically for current 
morning values. Skies will clear quickly from west to east today as 
dry air filters into the area. As mentioned, high temperatures 
should be the upper 60s to near 70 this afternoon before the 
stronger CAA arrives. Strong northwest winds will develop behind the 
front, but should be just shy of wind advisory criteria.
Moderate north winds will persist this evening and into the 
overnight hours as surface high pressure builds into Texas. Low 
temperatures tonight will fall into the lower to mid 40s. Sunday 
will be Chamber of Commerce weather with sunshine, light winds and 
slightly cooler than average temperatures in the lower to middle 60s.

LONG TERM (Sunday Night through Friday): Surface high pressure
will be in control of the weather across Deep South Texas late
Sunday and early Monday. This high should continue to build
eastward and northward very quickly allowing for winds to
transition to east and southeast in short order. With the return
flow, overnight lows Sunday/AM Monday will be slightly warmer.
This will be the rule (a warming trends) early next week as
southerly flow increases ahead of our next strong cold frontal
boundary due into the region early Wednesday morning. Before the
front moves through, winds will increase (may approach wind
advisory thresholds) on Tuesday and again on Wednesday. At this
point, looking at RH values, not expecting a widespread fire
weather threat midweek, however, with RH values in the 30 percent
range, cured fuels, and winds up to 30mph or higher...certainly 
can't rule out some marginal/limited fire weather concerns after 
the frontal passage on Wednesday. 

The main change in this package is the globals have finally 
agreed on a frontal passage Wednesday morning. Similar to the 
previous front, much of the rainfall will fall across the I69C 
corridor and points east, though we can't rule out a shower or two
for Zapata and Starr Counties. With some elevated instability 
around, can't rule out a clap of thunder or two as well.

By Thursday, a 1024mb high will sit over the TX Coastal Bend
region. This will help once again keep the area cool with
overnight lows dropping into the 40s for most and 30s for some.
This high pressure will quickly slide eastward. Another shot of
cooler air is forced southward down the MS River Valley toward the
end of the period. High pressure looks to settle across the bayous
of Louisiana early next weekend. Our temperatures during this time
will be moderated from an onshore flow. Precipitation outlook 
beyond Wednesday isn't very promising if you're looking for 

MARINE (Today through Sunday): Conditions will be less than favorable
most of the forecast. A cold front is nearing the coast. Strong 
northwest winds will arrive mid to late morning over the marine 
areas, and a gale warning (for expected gusts) will take effect at
14Z, along with a small craft advisory for the Laguna Madre. 
Strong winds and high seas will continue into tonight, with some 
improvement on Sunday as high pressure settles across the area. 
Conditions will gradually improve late in the weekend.

(Sunday Night through Friday): The long term begins with a brief
break in winds and seas before conditions gradually decline early
next week. Southerly flow will increase on Monday and especially
Tuesday out ahead of our next frontal boundary. Southerly flow
will likely lead to SCA thresholds being met during this time
frame. Beyond that, as the front pushes through, winds will
transition northerly and increase. Wind gusts up to Gale force is
currently expected Wednesday afternoon even across the Laguna.
High pressure will build southward by Thursday allowing for
conditions to improve by mid to late morning. Rather benign 
marine conditions are expected to take shape through the rest of 
the workweek before a subtle increase occurs again by the end of 
the period.

FIRE WEATHER...In the wake of a morning cold front, elevated fire
weather conditions will develop across deep South Texas and the Rio 
Grande Valley. While red flag warning conditions are not expected, 
there will be an elevated threat of erratic fire behavior beginning 
around 10 AM and continuing through about 6 PM. There will also be 
greater potential for rapid wildfire growth and spread.

Fine fuels such as grasses are considered cured. Relative humidity 
values will decrease to between 25 and 30 percent for inland 
counties for a few hours this afternoon. Northwest winds at 20 feet 
will range from 20 to 25 mph in the wake of the front.

Conditions will be monitored for the possibility of critical fire 
weather conditions if humidity values fall a bit more. the elevated 
fire danger conditions will decrease after sunset as temperatures 
decrease, relative humidity values rise, and winds diminish.

Relative humidity values will remain lower on Sunday, at around 25 
percent for most inland areas during the afternoon hours. However, 
winds will be lighter. Nonetheless, cured fuels and lower relative 
humidity values will mean the continuation of some fire danger 
threat, with increased potential for wildfire growth and spread.


GM...Small Craft Advisory for winds until midnight CST tonight for 

     Gale Warning until midnight CST tonight for GMZ170-175.

     Small Craft Advisory from 6 PM this evening to midnight CST 
     tonight for GMZ150-155.

     Gale Warning until 6 PM CST this evening for GMZ150-155.



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