Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/17/21
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
647 PM CDT Wed Jun 16 2021
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...Showers and thunderstorms continue to wane across
portions of Deep South Texas with clouds steadily dissipating. VFR
conditions will likely be the dominate category overnight with
flight categories lowering briefly to MVFR due to shallow patchy
fog development mainly near KMFE and KHRL. Tropical moisture
continues to increase across the region tonight with another
round of showers and thunderstorms developing Thursday with
increasing cloud cover. VFR should prevail with brief MVFR
conditions in and near the convection.
&&
.PREV DISCUSSION... /issued 303 PM CDT Wed Jun 16 2021/
SHORT TERM (Tonight through Thursday Night): Rinse and repeat for
todays forecast with a few sea breeze showers and storms developing
in coastal areas of the CWFA. More activity is noted offshore per
BRO radar and may push onshore later this afternoon. Much of this
activity should come to an end by late this afternoon. Shallow and
patchy fog may occur again late tonight/early Thursday morning
around sunrise as winds go nearly calm. Temperatures near seasonal
normal are expected for the remainder of today and into early
Thursday morning.
And now for something not completely, but slightly different. Invest
92L in the Bay of Campeche will begin to lift northward and enter
the central Gulf on Thursday, increasing the amount of tropical
moisture pushed onshore. This will lead to cloudier skies and some
enhanced precipitation chances especially near the coast and the
three easternmost counties in the CWFA. Overall precipitation
amounts appear fairly light, generally up to 0.10 inch with
localized higher amounts in any thunderstorms. Daytime temperatures
on Thursday will also remain a few degrees below seasonal normals as
a result of cloud cover and higher rain chances. Stay tuned to
updates from the National Hurricane Center on the anticipated
development of Invest 92L.
LONG TERM (Friday through Wednesday): The main two stories in the
long-term forecast continue to be the potential for tropical
cyclone development of Invest 92L in the southwestern Gulf of
Mexico in the next 24 to 48 hours and the intense heat anticipated
this weekend and into early next week.
The latest 1 PM CDT Tropical Weather Outlook from NHC has a 70%
chance of Invest 92L developing into a tropical cyclone
in the next 48 hours and a 90% chance of development in the next
5 days. A reconnaissance aircraft is scheduled to fly into the
area of low pressure sometime tomorrow. Latest deterministic
forecast models continue to trend the center and track of the
storm more and more eastward with each run. Still lots of
uncertainty at this time, especially since a depression/tropical
storm hasn`t yet formed. But even with the uncertainty, was
confident enough to go ahead and drop PoPs down about 10-20% for
Friday and Saturday from the previous forecast as models continue
to trend drier and warmer. Best chances of precipitation look to
be offshore over the Gulf waters on both days, but can`t rule out
isolated showers and thunderstorms, especially closer to the
coast. The main hazards that are expected (mainly for Friday and
Saturday) continue to be an enhanced threat of rip currents, rough
and high surf conditions, and the potential for some wave run-
up/minor coastal flooding at SPI and Boca Chica beaches.
As the potential tropical cyclone moves northeast of the area and
eventually making landfall across the northern Gulf coast, strong
ridging will build over the region that will cause substantial
subsidence beginning on Saturday. In addition, south to southeast
winds will make a return Saturday afternoon/evening, causing
dewpoint temperatures and relative humidity values to increase as
well. The combination of the abnormally hot temperatures and high
dewpoints will cause heat indices to spike between 110-115F on
Sunday afternoon, which may warrant a Heat Advisory for some
portions of the CWFA. The hottest day is forecast to occur on
Monday, where widespread high temperatures will rise into the
upper 90s to lower-mid 100s in most locations. With a very moist
airmass in place, dangerous heat indices are forecast to occur in
the afternoon, with maximum values ranging between 111-120F. If
these temperatures verify, an Excessive Heat Warning may be
needed for some portions of the CWFA on Monday.
Some relief in the heat may come on Tuesday as a weakness in the
mid/upper level ridge occurs as a longwave trough sweeps over the
central CONUS, helping push a weak cold front into central Texas
on Monday night. The front will likely stall and lift back north
before reaching South Texas on Tuesday morning. Though forecast
confidence remain very low for Tuesday, long-range models
indicate a build up of low-level moisture and rain along and ahead
of the cold front that may push into Deep South Texas during the
day on Tuesday and possibly lingering into Wednesday.
MARINE (Now through Thursday Night): Marine conditions will remain
favorable through this afternoon and evening as a result of light to
moderate easterly winds across the coastal waters. As Invest 92L
begins its trek northward late tonight and early Thursday morning,
conditions will then gradually deteriorate as swell from this
tropical system approaches the lower Texas coast. Building wave
heights and moderate easterly winds can be expected for Thursday
afternoon and evening as a result of a tightening surface pressure
gradient as 92L moves into the central and northern Gulf.
Friday through Monday: Generally slightly adverse to adverse
marine conditions are expected on the Gulf waters on Friday due to
Invest 92L moving into the central Gulf of Mexico. Small Craft
Exercise Caution may be on-going across the offshore Gulf waters
on Friday into Friday afternoon, then gradually pushing into the
near-shore Gulf waters by Friday evening. Small Craft Advisories
may be needed for the offshore waters periodically through Monday
as swell heights increase to over 6 feet. Isolated to scattered
showers and thunderstorms will be possible on Friday and Saturday.
&&
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 77 87 78 91 / 10 30 30 20
BROWNSVILLE 77 90 76 94 / 10 40 30 20
HARLINGEN 75 90 74 95 / 10 30 20 20
MCALLEN 74 91 73 96 / 10 20 10 20
RIO GRANDE CITY 73 94 72 98 / 10 10 10 10
SOUTH PADRE ISLAND 80 84 79 85 / 10 30 30 30
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
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