Area Forecast Discussion
Issued by NWS Brownsville, TX

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729
FXUS64 KBRO 190907
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
407 AM CDT Sat May 19 2018

.SHORT TERM (Now through Sunday): The axis of 500 mb high
pressure over the BRO CWFA is expected to continue to shift
slightly east, with the ridge becoming less prominent as a deep
mid-level trough becomes more enhanced along the west coast of the
United States. Although this pattern shift will allow for
increased convection over the neighboring high terrain of Mexico,
none of it is likely to intrude into Deep South Texas and the Rio
Grande Valley, where dry conditions are expected to persist. Above
normal daytime high and overnight low temperatures will also
continue.

.LONG TERM (Sunday night through Friday): A mid-level low
pressure system will dig southward across California at the
beginning of the week with ridging weakening ahead of it across
the Southern Plains. Higher pressure will ultimately dominant the
synoptic pattern, but a few shortwave troughs of low pressure will
move through the flow and provide a chance of showers and storms
early in the period. Moisture has been an issue the past several
days with strong subsidence aloft, dampening any possible rain
chances. However, models show a bit of hope with Precipitable
Water values rising to around 1.75" Sunday night into Monday along
with a vorticity maximum early on Monday. MOS guidance
probabilities have gone up across the Upper Valley the last couple
of model runs with convective-allowing models showing a few
stronger storms in the higher terrain of Mexico, which may move
across the border. With models still ranging quite a bit on PoPs,
was reluctant to go any higher than 30% for right now, though that
may be raised if better agreement occurs.

By mid week, the mid-level low lifts northward and the ridge takes
back over across our region through the rest of the week with ESE
flow at the surface. Rain chances will be slight at best with any
possible sea breeze, as a light easterly wind component may spark
a few showers along the coastal counties. Otherwise, hot and
humid conditions will be the story each day. Above-normal
temperatures in the upper 90s to perhaps the century mark out west
can be expected with Heat Indices rising above 100 across much of
the area.

&&

.MARINE (Now through Sunday): Buoy 42020 reported south-southeast
winds around 18 knots gusting to around 21 knots with seas slightly
under 4.5 feet with a period of 6 seconds at 150 CDT/650 UTC. The
Small Craft Advisory previously in effect for the Gulf of Mexico
waters for the overnight hours has been cancelled early due to a
lack of Advisory conditions. However, a Small Craft Advisory for
Winds has been posted for the Laguna Madre today in anticipated of
strong winds over the bay. Additionally, another Advisory may be
needed for the Gulf of Mexico waters tonight from 0 to 60 nautical
miles offshore due to the possibility of strong winds and rough
seas. A slight improvement in marine conditions is expected for
Sunday, with Small Craft Exercise Caution most likely for the Lower
Texas coastal waters.

Sunday night through Thursday: The pressure gradient will relax
for much of the period with moderate east to southeast winds
across the lower Texas coastal waters. A long fetch of easterly
flow across the Gulf may increase swells at the beginning of the
week, but seas should stay at around 3 to 5 feet each day.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  92  76  90  77 /   0   0   0  10
BROWNSVILLE          93  75  92  77 /   0   0   0  20
HARLINGEN            96  74  94  75 /   0   0   0  20
MCALLEN              98  75  95  77 /   0   0   0  30
RIO GRANDE CITY     100  74  97  76 /   0   0   0  30
SOUTH PADRE ISLAND   85  77  84  78 /   0   0   0  10

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory for winds from 9 AM this morning to 10 PM
     CDT this evening for GMZ130-132-135.

&&

$$

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

Short Term...66
Long Term...65



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