Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 180534 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1234 AM CDT Sun Jun 18 2017

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


.AVIATION...Some passing high level clouds and moderate southeast
winds prevail across Deep South Texas early this morning. A few
low clouds will drift across the area overnight and enough clouds
may briefly lower ceilings to around 1800 feet. Due to low
confidence and fairly dry air aloft, will not mention a MVFR
tempo group at this time. Otherwise, VFR conditions expected to
continue for the next 24 hours with high pressure in place. Breezy
conditions will develop later this morning, sustained winds
around 20 knots with gusts approaching 30 knots. Southeast winds
will gradually decrease to around 15 knots by late this evening.


.PREV DISCUSSION... /issued 644 PM CDT Sat Jun 17 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Cloud cover remains minimized by dry air and high
pressure aloft. CI beginning to move into the region from the
northeast will remain in the region overnight. This will also keep
cloud cover from forming closer to the surface through sunrise.
Sunday will be breezy again, with sustained winds around 20 knots
with gusts approaching 30kts. Temperatures will again soar,
reaching near 100 at KBRO and KHRL, and near 105 at KMFE. Heat
Index temperatures will likely reach at least 110 areawide, not
including any further influence from tarmac heating.

PREV DISCUSSION... /issued 306 PM CDT Sat Jun 17 2017/

SHORT TERM (Tonight through Sunday Night): A 500 hPa ridge anchored
over North Central and Northwest Mexico will support short term
subsidence and stability, as well as hot weather, over deep South
Texas and the RGV. Almost without saying, above normal to near
record high temperatures will prevail on Sunday. High temperatures
Sunday will range from the lower to mid 90s near the coast to triple
digits across portions of the Mid and Upper Valley. Heat index
values will be in the 105 to 110 degree range for a few hours over
most inland areas, and may even poke briefly into heat advisory
territory at places like McAllen and Rio Grande City. Surface low
pressure across West Texas interacting with high pressure across the
Gulf of Mexico will support moderate to strong southeast winds on
Sunday. Overnight low temperatures will range from 75 to 80 under
mostly clear to partly cloudy skies. Relative humidity values across
the Upper Valley will range from 25 to 35 percent Sunday afternoon
with 20 ft winds of 10 to 15 mph and with drying fuels. Thus,
monitoring of fire weather parameters should be sufficient for now,
with no supplemental fire weather products needed.

LONG TERM (Monday through Saturday): 500mb ridge across the
southwest United States Monday will continue to provide subsidence
across south Texas Monday through early Tuesday before any
impacts reach the CWA from the broad area of low pressure over the
Gulf of Honduras moves northwest across the Yucatan Peninsula
into the Gulf of Mexico Sunday into Monday. The global models
continue to show a wide range of possible tracks of the tropical
low assuming it develops into a tropical depression or tropical
storm during the next couple of days. The GFS continues to prog
the low moving towards the northeast Gulf Tuesday while the ECMWF
progs a westward track across the southwest Gulf approaching the
Mexican coast Wednesday. At this point with no tropical cyclone
defined yet and no official forecast track...will go with a blend
of the models for now which at least brings some rain
chances...mainly across the coastal sections of the
Wednesday through the rest of the week. Temperatures will still be
hot Monday and Tuesday but the increase in clouds and rain
chances through the rest of the forecast period may provide some
relief to the heat across the Rio Grande valley and northern

MARINE (Now through Sunday night): Moderate to fresh southeast
winds and moderate seas will prevail. Diurnal trends, driven in part
by low pressure over North and West Texas interacting with high
pressure over the Gulf, will support SCEC conditions on the Laguna
Madre by day and on the Gulf waters by night.

Monday through Thursday...Light east to southeast winds will
prevail across the coastal waters Monday with a weak frontal
boundary across northeast Texas and a tropical low possibly across
the southern Gulf of Mexico. The rest of the forecast is highly
dependent on the future track of the broad area of low pressure
over the Gulf of Honduras. Northeast winds may develop across the
western Gulf of Mexico Tuesday and increase assuming this feature
moves more to the west than expected. Even if the tropical low
moves more to the north than west...swells will develop across the
eastern Gulf of Mexico Monday into Tuesday and propagate westward
into the western Gulf of Mexico Tuesday into Wednesday.


GM...Small Craft Advisory for winds until 8 AM CDT this morning for



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