Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Brownsville Texas
1246 am CDT Tuesday may 26 2015
Discussion...updated for latest aviation discussion below.
Aviation...MVFR conditions have already developed locally...and
will remain steady overnight. Clouds will scatter out late
tomorrow morning...with VFR conditions through the day. Winds will
continue 5 to 10 knots overnight...rising to 15g20kts tomorrow.
Previous discussion... /issued 622 PM CDT Monday may 25 2015/
Discussion...updated for latest aviation discussion below.
Aviation...only changes made to the previous set of tafs were
to initial conditions. Previous aviation discussion follows:
Wind is the main issue this afternoon as southeasterlies cranking
at 20+ knots with gusts to 30+ knots along the Highway 77 corridor
including kbro/khrl...and expect this to continue through late
afternoon before things ramp down toward or just after sunset. The
wind machine is enhanced by the energy cruising across North Texas
as I write...and will ease off a bit on Tuesday though there will
be some gustiness by late morning.
Otherwise...another fairly typical day with enough low level
moisture to support a brief period of broken MVFR/low VFR ceilings
which will lift to low VFR in all areas and scatter out as dry air
spread from the west/southwest into the valley...with kmfe
improving soonest but khrl and kbro probably soon after. For the
prevailing period through 02/03z went for scattered through some
broken periods are likely for the first half of the period.
Overnight...expect the low MVFR ceilings to return toward midnight
and continue through early-middle morning before even drier air
arrives to scatter things out between 14/15z or so with ceilings
remaining in the high MVFR range.
Have removed all mention of precipitation...see earlier discussion
Previous discussion... /issued 249 PM CDT Monday may 25 2015/
Short term /now through Tuesday night/...some have termed the Rio
Grande Valley the 'land of wasted cape'...and the current big
picture 'puzzle pieces' are making the argument this afternoon.
Highly energetic short wave is creating messy weather from near
Austin into Oklahoma...and even produced a deadly tornado across the
Rio Grande from del Rio earlier this morning. With the wave lifting
northeast...any southward extension of the convective will favor
east/southeast Texas and leave deep S. Texas out of the action.
Very dry air moving in from 700-400 mb doesn't help the cause for
convective development with all the triggers well removed from the
tip of Texas.
The GFS and NAM both pick up on the general atmospheric drying and
lack of forcing...with raw data and guidance barely registering and
rainfall later this afternoon/evening. The European model (ecmwf) tries to develop a
very small area of 70% mean relative humidity along the tail of what's left of the
East Texas convection between sunset and 10 PM just southwest of
Starr County before dissipating it in Mexico...and the 18z hrrr
wants to do something similar but much earlier...as I write this a
little after 230 PM...which had not happened and looks spurious.
Bottom line? Have trimmed back rain chances and locations even
more for the remainder of the Holiday weekend...and killed off
altogether this evening (outside of a 10 percent silent chance).
Otherwise...benign weather is the rule later tonight through Tuesday
night. Whatever residual low level moisture is left early Tuesday
morning will be erased before noon...with a mix of sunshine and
clouds and slightly lower winds but a plenty warm atmosphere
allowing temperatures to tick up 1 to 2 degrees over this
afternoon...still a shade under guidance which isn't handling the
wet soil/evapotranspiration situation this Spring. The usual
overnight overcast returns sometime Tuesday night. Current
overnight/early morning forecast temperatures...75 to 80...look on
As for the rip/longshore current threat at area beaches...have
updated the statement to keep the hazard flowing given any late
visitors before they head home to work and school. Should be able
to let drop at midnight...or sooner.
Long term /Wednesday through Sunday/...a subtropical ridge will
build over the northwest Gulf and into Texas by Wednesday with
thicknesses increasing in step. High pressure will dominate the
north and west Gulf...resulting in seasonal weather with a mix of
clouds and sun and near to slightly warmer than normal temperatures.
The pattern should hold through Thursday when a middle level trough
nears from the southwest...increasing convection over West Texas and
The Big Bend through Thursday night. At the moment have kept the
forecast dry as the energy looks like it will stay north and west of
The subtoripcal ridge will flatten and spread west on Friday...with
a drier and more westerly flow upstream while the middle level trough
is pushed north. May see a sea breeze on Friday...both long term
models hint at it...and maintained higher probability of precipitation during the day as a
result. Could still see some nocturnal activity over the Mexican
mountains Friday night however. Meanwhile...the upper trough will
deepen into a better defined low over the Southern Plains while a
tropical system may form south of Baja California over the weekend...with upper
level moisture possibly teleconnecting northeast.
Marine /tonight through Tuesday night/...maintained Small Craft
Advisory hazard to buffer for Memorial Day boaters in the moderate
to potentially hazardous seas in the Gulf...but with system
exiting and area left under lighter winds off the surface (10-15
knots at 850 mb) for the balance of the period expect the usual
diurnal trends...which will favor caution /15-20 knots Gulf/ over
the Gulf overnight and the same for the Laguna Madre by day. Seas
have fluctuated between 5 and 6 feet but with steady state or
lowering winds expect 7 feet only in local situations through
Wednesday through Friday...subtropical ridging will build over the
northwest Gulf and Texas...with high pressure in control at the surface.
This will maintain a fairly consistent regime of moderate southeast
winds and upper end MDT wave heights. Small craft exercise caution
conditions look pretty solid on the Gulf much of the period due to
four to six feet wave heights. Southeast winds may increase slightly
Thursday night...becoming 15 to 20 knots due to upstream pressure falls
in advance of troughing over the southwest United States.
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