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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 190546 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1246 AM CDT Tue Mar 19 2019

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

.AVIATION...VFR is expected through the next 24 hours. Veering
winds throughout the forecast period and the opportunity for
precipitation towards the end will be the result of a trough at 
the surface that will shift westward. 
&&

.PREV DISCUSSION... /issued 647 PM CDT Mon Mar 18 2019/ 

DISCUSSION...Will let Coastal Flood Statement expire as scheduled
at 7 PM. Webcams at South Padre Island indicated that water was 
not washing up to the dunes, even at normally narrower spots on 
the beach, around high tide at 4:03 PM. Tidal gauges also show 
slightly lower readings vs. 24 hours ago. While these readings 
are still running nearly 1 foot above predicted levels, tomorrow 
afternoon's high tide is predicted to be lower than those of the 
past several days. Another complicating factor is the easterly 
swell that is expected to reach the coast late tonight or early 
tomorrow morning. So, while tidal overwash to near the dune line 
may return tomorrow afternoon, the current episode appears to be 
winding down.

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Area of light rain apparent on KBRO radar should move
east of all the aerodromes by 01-02Z. Thereafter, stubborn coastal
trough will continue to dominate the weather over the next 24
hours. Light northerly winds and VFR ceilings should continue
overnight. By mid-day Tuesday, the trough axis is progged to move
inland, shifting winds to NE and lowering CIG's to MVFR, as well
as increasing precip coverage due to convergence associated with
the trough.

PREV DISCUSSION... /issued 242 PM CDT Mon Mar 18 2019/ 

SHORT TERM (Tonight through Tuesday Night): Skies are overcast 
with light, low level north winds under more southwesterly flow 
aloft. There was an elevated inversion base at BRO this morning 
around 4 kft, and a few light showers continue to drift across the
CWA from west to east this afternoon, mainly in the saturated 
lower portion of the inversion. A trough of low pressure lies 
offshore, and moisture continues to funnel north along the trough 
axis.

Light rain chances will continue through the short term as the 
coastal trough remains largely in place and the upper pattern 
remains rather zonal. Subtle dips in the 500 mb pattern may provide 
weak enhancement of rain chances, though timing remains tricky. 
Showers may increase a little in coverage for the lower valley 
tonight as one of these weak pulses moves overhead. Temperatures 
will be below normal for this time of year.  Look for 50s and some 
60s overnight, and mid to upper 60s Tuesday during the day. 
Otherwise, the cloud, cool weather with spotty light showers will 
continue through the next 36 hours.

LONG TERM (Wednesday through Monday): Highly amplified pattern
sets up for the latter half of the week, with large trough diving
along the east coast, and another trough ejecting into the Four
Corners region. This leaves Texas in ridging between, so active
weather will be minimized. There is a little isentropic lift
trying to set up Wednesday and Thursday, so the latter half of the
week will still see cloudy skies and light precipitation. 

Friday and Saturday the western trough moves eastward into the
Central Plains. This will bring better diffluence aloft, along
with more scattered vorts embedded in the southern edge of the 
trough. This will lead to a better chance for showers and 
thunderstorms, vs. the gray and drizzly pattern before it. While 
the midlevel energy will be present, the lack of a surface forcing
mechanism will limit the chances for organized convection, so 
shower activity Friday and Saturday will be scattered, with better
chances to the north closer to the main part of the trough. 

Sunday the leading edge of the trough will be moving north, lack
of midlevel support will lower rain chances. Models have continued
to back away from the next frontal passage, and are now waiting
for the trailing lobe of the larger-scale trough to swing around
into Texas Sunday night, driving the dryline southeastward on
Monday. Still low confidence on it getting to south Texas, but if
this pattern holds out, it would bring light south to southwest
flow to the valley, which would push temperatures well into the
90s a week from now.

MARINE:
Now through Tuesday night: Coastal troughing will remain in place
through Tuesday night, supporting moderate northeast to east 
winds. A long Gulf fetch will provide a swell contribution, 
resulting in elevated Gulf wave heights. Small craft should 
exercise caution to low end small craft advisory conditions will 
be possible on the Gulf tonight through Tuesday night.

Wednesday through Saturday: For the remainder of the week, winds
will remain nearly easterly with high pressure across the lower
Mississippi valley. Winds would remain around 10 knots, but the
long fetch would continue to press long period swells up against
the coast. Southeast flow would finally reestablish Friday night
into Saturday as the high moves east and low pressure tries to
form in the Panhandle. Winds would likely remain at or below 15
knots, as the Panhandle low has trouble organizing to start.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for hazardous seas from 7 AM this morning 
     to midnight CDT tonight for GMZ170-175.
&&

$$

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