-- Discussion containing changed information from previous version are highlighted. --
587
FXUS64 KBRO 231124 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
624 AM CDT Thu May 23 2024

...New AVIATION...

.SHORT TERM...
(Today through Friday)
Issued at 302 AM CDT Thu May 23 2024

500 mb high pressure centered over the Bay of Campeche, and
extended over the BRO CWFA, will continue to be the dominant
weather feature through the period. The persisting effect of this
synoptic weather set-up will be not only dry weather, but also
well above normal daytime high temperatures. As was the case 24
hours ago, NBM guidance appeared slightly too cool for high
temperatures today, so increased these a degree. Once again, this
yielded heat index values at, or slightly above, HEAT ADVISORY
criteria for all of Deep South Texas and the Rio Grande Valley
except the island portions of Cameron, Willacy, and Kenedy
counties today, and as a result, a HEAT ADVISORY is in effect for
this specific area for half a dozen hours. An additional HEAT
ADVISORY is likely to be needed on Friday for the same area.

&&

.LONG TERM...
-- Changed Discussion --
(Friday night through Wednesday)
Issued at 302 AM CDT Thu May 23 2024

No major changes on the extreme heat forecast for the holiday
weekend. Dangerous heat indices along with record high temperatures
and much above normal overnight low temperatures remain in the
forecast through at least Tuesday morning. Models begin to show
some relief Tuesday and more so Wednesday as the anomalous mid-
level ridge over N Mexico and S Texas gets shunted southward (just
a bit) with a cold front indicated to undercut the ridge as it
drops into Central Texas.

Ensemble members continue to show 850mb temperatures in the 27-31C
range or 2-4 standard deviations above normal across Deep South
Texas Saturday-Monday. Latest deterministic model temperatures
guidance ranges from near 90 at SPI, 95 to 110 degrees each
afternoon for inland locations with not much relief ovenight with
lows in the 77-85F range. Of course, the continuation of moderate to
occasionally strong onshore flow will maintain elevated dew points,
resulting in extreme heat index values reaching 110-120+ degrees.
The NWS Heat Risk product continues to indicate most of the CWA
in the Extreme category for Sat-Mon which will lead to Heat
advisories and Excessive Heat Warnings. This will be a
particularly dangerous situation with the extreme heat indices
possibly leading to heat related illnesses especially since more
people are likely to be outdoors for the Memorial Holiday weekend.

Relief may be on the way the middle of next week with all ensemble
and deterministic models trending lower on the overall temperature
profile.  GFS/ECMWF show 850mb temps in a more reasonable range of 20-
27C with the GFS cooler than the ECMWF. A cold front is shown to
undercut the mid-level ridge settling over Central Tuesday and South
Central Texas Wednesday. This should lower ambient temperatures 4-8
degrees across the board and possibly bring a low chance 10-20{%) of
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
(12Z TAFS)
Issued at 622 AM CDT Thu May 23 2024

A breezy to windy onshore flow will combine with partly to mostly
cloudy skies to produce MVFR to VFR at the aerodromes through the
next 24 hours.
-- End Changed Discussion --

&&

.MARINE...
Issued at 302 AM CDT Thu May 23 2024

Today through Friday: Buoy 42020 reported southeast winds around
18 knots gusting to around 21 knots with seas slightly over 6 feet
with a period of 7 seconds at 1:50 CDT/6:50 UTC. An enhanced
pressure gradient will continue along the Lower Texas Coast during
the period courtesy of high pressure over the western Gulf of
Mexico interacting with thermal low pressure over inland Mexico.
Generally breezy winds and moderate winds are likely, as is Small
Craft Should Exercise Caution for portions to all of the lower
Texas coastal waters.

Friday night through Wednesday: Broad surface ridging persists
over the Gulf of Mexico through the holiday weekend. A combination
of a pressure and thermal gradient will continue to produce a
moderate to occasionally strong southeast to south wind and a
moderate sea. The strong winds with the potential for small craft
advisories are trending for Sunday as a deepening low pressure
area moves across the Central Plains. The gradient begins to relax
next Monday and Tuesday as a cold front edges into Central Texas.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             95  81  96  81 /   0   0   0   0
HARLINGEN               98  78  99  79 /   0   0   0   0
MCALLEN                101  81 102  81 /   0   0   0   0
RIO GRANDE CITY        104  80 106  79 /   0   0   0   0
SOUTH PADRE ISLAND      88  83  88  82 /   0   0   0   0
BAYVIEW/PORT ISABEL     94  80  94  80 /   0   0   0   0

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory from 1 PM this afternoon to 7 PM CDT this evening
     for TXZ248>255-351-353>355.

GM...None.
&&

$$