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Area Forecast Discussion (AFD)

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

FXUS64 KBRO 221802 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
102 PM CDT Sun Sep 22 2019

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


.AVIATION...VFR conditions prevail now with few to scattered low 
clouds in southeast to northwest streets across the CWA, along 
with light to moderate southeast winds. There is a bit of low 
cumulus convergence along the sea breeze this afternoon, with any 
ceilings staying above 3 kft. Isolated sea breeze showers are 
along the I-69E corridor in Kenedy County, and a few more may form
farther south into Willacy and Cameron later this afternoon. 
Conditions should stay VFR through tonight, with a few low clouds 
again in the morning associated with coastal streamer showers. A 
few high clouds, mainly associated with upper moisture being 
dragged over West and Northwest Texas, may get into the picture 
locally overnight as well. Surface winds will drop to light 
southeast overnight. Patchy ground fog will be more likely inland,
with guidance not picking up a strong signal at the TAF sites.


.PREV DISCUSSION... /issued 623 AM CDT Sun Sep 22 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...VFR will continue to be the rule through the next 24 
hours. Moderate winds with breezy gusts are anticipated for the 
daylight hours of today before diminishing around sunset. Isolated
convection will occur, but still will not be widespread enough to
warrant inclusion in the TAFs for the aerodromes. 

PREV DISCUSSION... /issued 355 AM CDT Sun Sep 22 2019/ 

SHORT TERM (Today through Monday): KBRO Doppler radar shows a steady 
stream of isolated showers transitioning from the Gulf of Mexico to 
the inland areas at this time, no doubt supported by the 1.97 inches 
of precipitable water recorded by the Saturday evening local upper 
air sounding. This relatively deep tropical moisture will persist at 
the same time an inverted 500 mb trough continues to approach the 
BRO CWFA from the east. The result of this weather scenario will be 
isolated convection within Deep South Texas and the Rio Grande 
Valley during the forecast period. The recent trend of above normal 
daytime high and overnight low temperatures will continue given the 
expected low rain chances and limited cloud cover. 

For the local beaches, will allow the Coastal Flood Statement to 
continue until mid-morning today given the predicted astronomical 
tides and the observed swell moving towards the Lower Texas Coast.

LONG TERM (Monday Night through Saturday): Across the mid-levels
of the atmosphere, Deep South Texas will sit in between a 500 mb
ridge across the eastern Gulf of Mexico and a cutoff low across
the Desert Southwest to begin the long term period. Additionally,
a weak inverted trough moving around the flow of the ridge will 
linger within our general region before eventually lifting out
as the cutoff low begins to open up into a trough and progresses
towards the central plains. The 500 mb ridge positioned to the 
east will then expand westward into the region from late in the 
workweek and into next weekend.

Despite the presence of the weak inverted trough over the region 
from early to midweek, model atmospheric profiles and time heights 
do indicate that some dry air remains within the mid-levels of 
the atmosphere. The ECMWF continues to show more pronounced dry 
air aloft compared to the GFS. ECMWF MOS output has continued to 
trend lower in regards to the pops through midweek than the GFS
MOS output. The ECMWF then becomes more in line with the GFS pops
for Friday into the weekend. Elected to remain persistent with a
slight chance for convection each day through the long term, with
primary focus along the seabreeze each afternoon to the east of
highway 281.

Above average temperatures will remain expected through the long 
term period despite the weakness aloft early to midweek. Expect
subtle rise in temperatures and heat indices late in the week as 
the 500 mb ridge to the east builds back westward. With the dry
air aloft on the ECMWF as noted in the previous paragraph, the
model output continues to indicate warmer temperatures then the
GFS solution. Like previous inherited forecasts, I will continue
to go with a blend but with more of a lean closer to the warmer 
ECMWF output. Heat indices will peak between 100 to 105 degrees
early in the period and between 105 and 110 degrees later in the

The tropical Atlantic basin remains active with Tropical Storm 
Jerry south of Bermuda, Tropical Storm Karen which recently
developed near the southern windward islands and the high 
probability for the development of a tropical cyclone off the 
western African coast. The Eastern North Pacific Basin is also 
active with Tropical Storm Kiko, Tropical Storm Lorena and 
Tropical Storm Mario. This serves as a good reminder to stay
prepared and keep updated with the latest tropical systems at

MARINE (Now through Monday): Buoy 42020 reported southeast winds
around 14 knots gusting to around 18 knots with seas slightly 
over 5 feet with a period of 9 seconds at 150 CDT/650 UTC. 
Moderate swells from the east will produce Small Craft Exercise 
Caution along the Lower Texas Coast during the period, especially 
for the Gulf of Mexico waters between 20 and 60 nautical miles 
offshore. Otherwise, mariners can expect light to moderate winds 
and generally moderate seas. 

Monday night through Saturday: Light to moderate south to 
southeast winds and moderate seas will continue due to broad 
surface high pressure across the Gulf of Mexico. Anticipate at
times for small craft exercise caution to near marginal small 
craft advisory conditions during the period. Expect isolated to 
scattered marine showers and thunderstorms throughout the period.
Any heavier cells may result in locally gusty winds and locally 
enhanced sea state. 




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