Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 221746
Area Forecast Discussion
National Weather Service BROWNSVILLE TX
1246 PM CDT FRI JUL 22 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Sea-breeze front continues to march inland per latest
visible satellite, radar, and surface observations. Main aviation
forecast challenge is timing the beginning and end of showery
precip at the terminals this afternoon. (Not expecting any
thunder as instability aloft is somewhat limited.) Sea-breeze
pretty well through at BRO, though a few showers lingering in the
vicinity to the west. Will go with -SHRA there but only until
1830Z. Impact at HRL should be mainly confined to 18-19Z so
inserted a TEMPO line for -SHRA there but will, of course, have to
monitor. Not quite as confident on the line of showers reaching
MFE per short-term model guidance, so will word VCSH there 19-21Z.
Once sea-breeze showers clear the terminals, VFR prevail with
light winds and clear skies overnight yielding to a few SE breezes
by mid-morning on Saturday.
.PREV DISCUSSION... /issued 531 AM CDT FRI JUL 22 2016/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...Isolated to scattered showers will continue offshore
for a few more hours as depicted by the HRRR, but will then
fizzle after daybreak and heading deeper into the day. A sprinkle
may reach Brownsville in the next couple of hours, however, MFE
picked up early morning BKN MVFR ceilings, which has been typical
recently, but still expecting VFR conditions overall for the TAF
sites today with any ceilings lifting above 3 kft. As the day
progresses, a light to moderate east wind with few to sct low
clouds at around 3500 or so ft will prevail, in other words VFR
conditions. Guidance is lean on any daytime showers despite ample
moisture. Thus, won`t carry any precip in the TAFs right now, but
a small potential is there.
PREV DISCUSSION... /issued 359 AM CDT FRI JUL 22 2016/
SHORT TERM (Today through Saturday): A fairly expansive mid level
height center positioned over the southern high plains and extending
from southern California to the lower Mississippi Valley will
provide a measure of stability and persistence to the local
forecast. Fair skies with an occasional smattering of low clouds
along with light to moderate east to southeast winds and warmer than
normal temps will predominate through the short term. Afternoon Heat
index values from 103 to 108 degrees will be possible in some areas
like Starr County, but otherwise 100 to 105 degree heat index values
will be more common. The onshore flow will keep dew points in the
70s, with PWAT values above avg in the upper quartile of the one to
two inch increment. Nonetheless, PoP will remain mostly in the
slight or isolated category via model guidance. May see some coastal
showers overnight, and the sea breeze could result in a few hit or
miss showers during the day. Winds will veer from east today to more
southeast on Friday as high pressure reorients slightly. Otherwise,
conditions will be generally similar to what we`ve been seeing the
last few days.
LONG TERM (Saturday Night through Thursday): Models remain in
good agreement but consistency has faltered slightly on the timing
of the mid level inverted trough expected to move across the
Northern Gulf middle of next week.
In advance of this mid level feature the elongated ridge of high
pressure continues to drift west allowing for mid and upper level
winds to back northeast advecting in slightly mid level drier air.
The combination of subsidence from the ridge and the drier air
will keep rain chances below 20 percent Sunday and Monday. As we
move into Tuesday-Thursday weak inverted troughs track west across
the Gulf. One originating from an East coast trough tracks slowly
across the Northern Gulf and a weaker trough of tropical origin
traverses the Southern Gulf. The combination of these two
increase the mean relative humidity values through the atmosphere
column bumping up the chances for sea breeze convection. Will
maintain isolated to scattered coverage with better upper
forcing/support remaining north of our CWA associated with the
stronger northern trough. Little change in the temperature
forecast with highs a few degrees warmer Sunday and Monday and
maybe a degree or two lower Tue-Thu with the increase in
convection, but not appreciably noticeable with heat indices
remaining in the 100-109 range.
MARINE:Today through Saturday...A large scale ridge centered
over the south central United States is spread over territory
from southern California to the lower Mississippi Valley, and is
also supporting broad high pressure over most of the Gulf of
Mexico. Light to moderate onshore winds and low to moderate seas
will therefore prevail in the short term. Isolated showers may
occasionally develop and move north along the coast.
Saturday night through Tuesday...Weak surface high pressure to
persist across the Gulf of Mexico to combine with lower pressure
across the Southern Gulf maintaining a light to occasional
moderate east to southeast wind and a slight sea regime. showers
and thunderstorms to increase in coverage Tuesday and Wednesday.
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