Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 181936

Area Forecast Discussion
National Weather Service Brownsville TX
236 PM CDT Tue Sep 18 2018

.SHORT TERM (Tonight through Wednesday Night): Mid level ridging is in
place over Texas, shifting east toward the lower Mississippi Valley,
with high pressure at the surface across the northwest Gulf.
Moisture is near average, with precipitable water this morning at
Brownsville checking in at 1.88 inches, and should remain around
this value in the short term. Mostly clear skies will develop
tonight after diurnal heating subsides, with overnight low
temperatures in the mid to upper 70s. Few to scattered Gulf based
low clouds will set up in the early morning hours.

The slow eastward movement of the overhead H5 ridge on Wednesday may
open the door to a bit more instability over the area, with slightly
higher, i.e. mentionable, pops. Isolated showers, either triggered
by or enhanced by the sea breeze, will develop and move northwest
over the coastal and mid valley areas by afternoon. The ECMWF is a
bit a little more aggressive than other models with rain chances,
but overall the models are in general agreement with an increase in
rain chances on Wednesday. Will hold off on introducing thunder this
go around.

Otherwise, temperatures will be just a few degrees above average,
with afternoon high temperatures in the 90s, and light winds
overnight becoming southeast each morning, then east southeast with
a modest pickup in the afternoon, courtesy of a westward pushing sea
breeze. Skies will be partly sunny by day and mostly clear at night,
with some morning stratus development over the ranchlands that will
burn off quickly by mid morning.

.LONG TERM (Thursday through Tuesday): As the upper level ridge
slides eastward into the southeast United States, an upper level
trough will be pushing deeper into Texas from the west. This
should be just enough support coupled with the sea breeze to
generate scattered showers and T`storms across the CWFA. The best
chances look to remain across the northern Ranchlands at this
time, closer to the trough axis and better lift.

The ECMWF brings a very weak cold front into central TX by late in
the weekend. The front doesn`t quite make it down this way before
it washed out along the I10 corridor or just north. An upper level
high builds into the area bringing drier air and subsidence,
however, globals still ping some QPF (likely from a very rich
boundary layer) for late this weekend and early next week. Kept
"slim" POPs going through the end of the period. Just beyond the
scope of this cycle, another frontal boundary appears on the
Globals. Timing and strength vary from model to model, but it is a
reminder that autumn may not be too far away.


.MARINE (Tonight through Wednesday Night): Light southeast winds will
become moderate after Wednesday, with high pressure staying in
control over the Gulf. Low to moderate seas will persist through
the short term. Isolated showers will be present, especially
Wednesday into Wednesday night.

(Thursday through Tuesday): Southeasterly flow will begin to
increase to start the long term. This will cause moderate winds
and seas with a sufficient southeasterly fetch. That said, not
expecting anything more than low-end cautionary wording (if that).
Gradual improvement is expected through the upcoming weekend and
early next week as surface pressure gradient relaxes allowing
winds and seas to become light. Can`t rule out scattered
convection from time to time, especially early in the forecast
period. The proximity of showers/T`storms may locally cause a
subtle increase in seas and winds.


BAYVIEW/PORT ISABEL  78  91  79  91 /  10  10  10  30
BROWNSVILLE          77  93  78  93 /  10  20  10  30
HARLINGEN            75  94  77  94 /  10  20  10  20
MCALLEN              78  95  78  95 /  10  20  10  20
RIO GRANDE CITY      77  96  77  96 /  10  10  20  20
SOUTH PADRE ISLAND   80  89  80  89 /  10  10  10  30




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