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Area Forecast Discussion (AFD)

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

                            
000
FXUS64 KBRO 210855
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
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.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  91  78  91  78 /  20  20  20  20 
BROWNSVILLE          94  77  94  77 /  20   0  20  20 
HARLINGEN            95  76  95  75 /  20   0  20  20 
MCALLEN              98  77  97  77 /  20   0  20  10 
RIO GRANDE CITY      99  76  98  76 /  20   0  20   0 
SOUTH PADRE ISLAND   87  81  88  81 /  20  20  20  20 

&&

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

$$

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

Short Term...Tomaselli/66
Long Term/Graphics...Brady/62
Climate/Upper Air/Graphics...Caceres/63