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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 240515 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1215 AM CDT Fri May 24 2019

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

.AVIATION...VFR to MVFR will be the rule through the next 24
hours. Breezy winds through the remainder of the overnight hours
will become even more windy on Friday. Convection continues to be
not anticipated or likely. 
&&

.PREV DISCUSSION... /issued 716 PM CDT Thu May 23 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...MVFR cigs are likely to increase in coverage this
evening and overnight persisting through at least mid-morning
Friday. Daytime mixing to allow for the BKN-OVC MVFR to lift and
become SCT-BKN VFR Friday afternoon. Pressure gradient remains
tight with a persistent 15-25 knots southeast flow tonight 
through Friday. Some gusts to 30 knots. 

DISCUSSION...Updated for latest marine discussion below.

MARINE...Winds across the Southern Portions of the Laguna Madre
have subsided below 20 knots while winds remain rather strong and
gusty over the Mid and Northern reaches of the Laguna Madre. Winds
north of Port Mansfield to remain near 20 knots overnight so have
extended the SCA for these northern marine zones. 

PREV DISCUSSION... /issued 252 PM CDT Thu May 23 2019/ 

SHORT TERM (Now through Friday Night):  A 595 dam ridge will remain 
entrenched/centered over the lower Southeast United States through 
Friday night, supporting high pressure over much of the Gulf. The 
ridge and surface high pressure will extend west to cover portions 
of Texas. A synoptic scale mid level trough will remain upstream 
over the Southwest United States and out of play weather wise as far 
as the local area is concerned. This pattern will maintain a dry and 
subsident/stable atmosphere over the area through the short term. 
Low temperatures will run in the middle to upper 70s while high 
temperatures on Friday will run in the 90s for most inland areas. 
Short term temperatures will be slightly above average for this time 
of year. Heat index values will range from 100 to 105 degrees for 
portions of the CWA for a few hours Friday afternoon. Light to 
moderate south southeast winds will persist through the short term 
under partly to mostly cloudy skies.

LONG TERM (Saturday through Thursday): Overall, hot, humid, and 
breezy weather is expected to continue through the Memorial Day
holiday weekend and right on through most of the work-week
following. There may be a glimmer of hope for the return of
chances for measurable precip by late next week, but not too much
to hang one's hat on at the moment.

Current water-vapor satellite imagery/upper-air analysis shows
upper-level ridge axis spilling down into the southwestern Gulf of
Mexico from subtropical high center centered over the SE CONUS.
Short-wave troughs rotating around the mean western CONUS trough
will attempt to flatten the upper ridge in our vicinity from
time-to-time, but all indications are that it will bounce back 
each time with little appreciable change in the sensible weather.

All this adds up to more heat, which, while uncomfortable, won't
really be too far out of line climatologically as we approach the
start of meteorological summer on June 1st. Heat indices in many 
areas should top out the 101-107F each day through at least 
Wednesday. The "saving grace", if you will, over the holiday 
weekend may be that the atmospheric column should be dry enough 
aloft for some of those higher dewpoints to mix out a bit in the 
afternoons, particularly from Saturday through Monday and over the
eastern CWA (closer to the center of high aloft). Afternoon 
dewpoints will hopefully be more in the lower 70s for the 
populated RGV, as opposed to the 79-80F observed at BRO as of this
writing.

With the persistent SE breeze, can't rule out some light "streamer"
showers along the coast at night as we move into next week. This
would mainly kick in Monday night onward as the low-level flow
veers more SSE and strenghtens a bit more. As we head toward
Thursday-Friday of next week, some mentionable PoP's have been
reintroduced into the forecast. GFS hinting at inverted
troughiness moving into the Yucatan region; ECMWF stalls a front
over north/central TX. Either solution would weaken and back the 
surface flow somewhat locally, which would add the potential for 
a more activated sea-breeze. Any showers/thunderstorms could help 
our abnormally dry conditions which have developed in Cameron and 
Willacy counties.

MARINE (Now through Friday Night):  Moderate to strong southeast
winds and elevated seas will persist through the forecast. 
Surface high pressure anchored over the Gulf of Mexico will 
support a tight pressure gradient and the related stronger winds 
and higher wave heights. A significant swell component will aid in
keeping wave heights higher. Laguna Madre conditions should 
improve to small craft should exercise caution tonight, but 
elevated seas on the Gulf will keep small craft advisory 
conditions going. Tides will continue to run above predicted 
values by about half a foot. Some beach runup will therefore be 
possible, especially around the time of high tide. Rip current 
risk will remain elevated in the short term.

Saturday through Wednesday: Pressure gradient is expected to
remain enhanced across the western Gulf through the period, as
high pressure over the SE CONUS and adjacent Atlantic waters
interacts with lower pressure over the Plains. This will drive
moderate to occasionally fresh winds over the coastal waters,
generally from a southeasterly direction. Overall, winds will
favor Small Craft Exercise Caution (SCEC), possibly ticking up 
toward lower-end Small Craft Advisory (SCA) levels at times.
Higher wind speeds will tend to favor the Laguna Madre during the
afternoons and Gulf waters later at night. With the persistent SE
flow, swells should help keep total seas generally in the 5-6 ft.
range. SCA wind/sea conditions look more likely to occur
periodically from Monday night onward.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds until 6 AM CDT early this morning 
     for GMZ132-135.

     Small Craft Advisory until 6 AM CDT early this morning for 
     GMZ150-155-170-175.
&&

$$

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