Preview of NWS' New Version of Forecast
This preview is not operational and should not be used for support decisions.

Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 211847 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
147 PM CDT Sat Sep 21 2019

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

&&

.AVIATION...The afternoon heating has fired off some spotty shower
activity across portions of Deep South TX this afternoon. Most of
this activity is moving to the NW and is remaining well north of
the RGV airports. These showers should dissipate with the loss of
the afternoon heating later today allowing for VFR conditions to
prevail throughout the overnight period. Expect another round of
isold conv driven by the daytime heating tomorrow afternoon. This
will likely keep the ceilings/vsbys at VFR levels for all three
RGV airports through the upcoming 24 hours.  

&&

.PREV DISCUSSION... /issued 537 AM CDT Sat Sep 21 2019/ 

DISCUSSION...Updated for latest aviation discussion below.

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

PREV DISCUSSION... /issued 355 AM CDT Sat Sep 21 2019/ 

SHORT TERM (Today through Sunday): The most recent KBRO upper 
air sounding revealed a precipitable water content of 1.78 inches 
in the atmospheric column. This relatively deep moisture will 
persist through the forecast period, and when combined with the 
approach from the east of a weak inverted 500 mb trough, isolated 
showers will result across the BRO CWFA. Above normal temperatures
are also anticipated due to the limited rain chances and 
corresponding lesser cloud cover.

LONG TERM (Sunday Night through Friday): The 500 mb mid-level
ridge stretched across the gulf coast states to start the period 
will gradually break down and slide towards the southeast through 
early to middle of next week. An inverted trough in the southern 
Gulf of Mexico will be expected to move around the periphery of 
the weakening ridge. This inverted trough is expected to move 
into/across our region early in the week. The latest runs keep 
this weak disturbance or at least mid-level weakness across the 
region through midweek while a cutoff low is positioned across 
the southwest U.S. Late in the period, mid-level ridging will 
nudge back westward into our region as the cutoff low opens up 
into a shortwave and propagates into the central plains. The
models, however, do show a possible second inverted trough 
approaching the region by next weekend.

The latest model blends and MOS guidance continue to highlight 
that Monday features the best chance for convection across the 
region with pops as high as 30/40 percent. Slight chances for 
showers and thunderstorms will otherwise trend through Friday, 
with best chances along and east of highway 281 with the sea 
breeze. The ECMWF is notably drier after Monday compared to the 
GFS. As a result, the ECMWF guidance is also trending a bit 
warmer compared to the GFS output as well. I have elected to 
trend closer to the warmer side of the guidance throughout the 
long term period with afternoon high temperatures still above 
average levels with higher heat indices. However, I did drop 
the overnight lows by a degree or two for quite a few locales, 
especially for portions of the northern ranchlands.

MARINE (Now through Sunday): Buoy 42020 reported east-southeast 
winds around 16 knots gusting to around 19 knots with seas 
slightly under 4.5 feet with a period of 6 seconds at 250 CDT/750 
UTC. An enhanced pressure gradient over the western Gulf of Mexico
will continue to produce breezy winds and moderate seas along the
Lower Texas Coast. Small Craft Exercise Caution will likely be 
needed for portions or all of the lower Texas coastal waters 
during the period. 

Sunday night through Friday: Light to moderate south to southeast
winds and generally low to moderate seas of between 3 to 5 feet 
will be expected throughout the long term period as a result of a
rather modest pressure gradient at the surface. Winds and/or seas
could reach small craft exercise caution levels at times. Small
craft advisory conditions are not expected. Isolated to scattered
marine showers and thunderstorms will remain possible through the
period. Any heavier cells may result in locally gusty winds and
locally enhanced sea state.

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

This product is also available on the web at:
HTTP://WEATHER.GOV/RGV

Short Term/Aviation...60
Long Term...54