Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 212333 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
633 PM CDT Fri Jul 21 2017

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


.AVIATION...VFR conditions to prevail tonight and Saturday with
high pressure overhead maintaining drier air through the
atmosphere. An upper level low pressure area over the North
Central Gulf of Mexico to drift west while weakening tonight and
Saturday. An isolated shower or even a thunderstorm is possible
over the coastal waters east of Padre Island. Gusty winds early
this evening to diminish an hour or two after sunset before
increase Saturday mid to late morning as the pressure gradient
tightens across South Texas. Southeast wind to gust between 22-28
knots Saturday afternoon.


.PREV DISCUSSION... /issued 258 PM CDT Fri Jul 21 2017/

SHORT TERM (Tonight through Saturday Night): Not much change to
the short term forecast, as the summertime ridge remains the main
influence on local weather. The cutoff low across northern Florida
will drift west along the Gulf coast during the next 36 hours,
but will not arrive during the short term period. The ridge will
continue to produce hot temperatures areawide. Highs tomorrow will
increased at or above 100 degrees for all except eastern Cameron
County, as models were not handling the increased heat noted in
the western valley the past 3 days.

LONG TERM (Sunday through Friday): No significant changes have
been made to the long term forecast for this afternoon package.
The period begins in the middle of a hot and dry stretch of
weather as large, highly amplified mid-level ridge sits over much
of the Western U.S. This will keep generally keep subsident
condition in place across Texas. This will be reinforced by the
western edge of a weak low/inverted trough that will be over Deep
South Texas. This weak low will shift further inland across Texas
on Monday, however moisture will be slow to return on the back
edge of it, and have kept Monday dry as well. High temps will run
from the mid to upper 90s near the coast to around 105 degrees
across the Mid to Upper Valley. Heat index values will easily
range from 105-110 both days.

A small surge of moisture does appear to make a come back by
Tuesday and Wednesday as the trough pushes west and generally
dissipates around the periphery of the high pressure ridge.
However, models are still in some disagreement, with the GFS
still holding in to slightly higher chances than the ECMWF, which
continues to indicate the best moisture remaining south of the
region. Given the continued uncertainty have kept the small slight
chance to chance POPs. There should be at least some increased
cloud cover as well, which would help keep temperatures a little
cooler. However, have increased them slightly by a degree or so.

By the end of the period, the H5 ridge looks to stretch east and
become centered across the Southern Plains in responds to a
developing Eastern Pacific tropical system. This will effectively
shutoff the taps for the RGV with the dry/hot streak of weather


Today through Saturday night: Seas continue around 2 feet today
as wind profile across the Gulf remains light. Conditions will
begin to change starting tomorrow as a front moves into Oklahoma
and north Texas, tightening the gradient in the vicinity.
Southeast winds tomorrow will reach near 15 knots for the open
Gulf waters, and 15 to 20 knots for the Laguna Madre. No
advisories are currently expected, but mariners will likely need
to Exercise Caution during the day Sunday, and Sunday night across
the open Gulf waters.

Sunday through Tuesday: Broad high pressure over the Eastern Gulf
will interact with a surface low pressure system over the
Panhandles region of Texas and Oklahoma on Sunday through Monday.
This will strengthen the surface pressure gradient and cause
winds to increase to near 15 to 20 kts from the SE. Seas will
increase from around 4 to 5 feet. By Tuesday, the high over the
Gulf will shift westward, decreasing the pressure gradient and
allowing seas and winds to relax.


BAYVIEW/PORT ISABEL  80  97  80  95 /  10  10   0  10
BROWNSVILLE          79  96  79  96 /  10  10   0  10
HARLINGEN            78 100  78  99 /  10  10   0  10
MCALLEN              80 103  80 103 /  10  10   0  10
RIO GRANDE CITY      78 106  78 104 /  10  10   0  10
SOUTH PADRE ISLAND   82  92  82  89 /  10  10   0  10




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