Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 302352 AAA
Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
652 PM CDT MON MAY 30 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Aviation conditions have improved to VFR this evening
after a round of convection moved through the area earlier today.
Conditions should be relatively quiet now for the next few hours,
but radar shows developing activity upstream moving east. Showers
and thunderstorms will increase in coverage out west later tonight
and will move across the area, but short range model output is
also picking up a mid level wave moving east from the Big Bend/
West Texas area overnight. This feature may support a line of
convection at the surface which will move through the lower valley
and the TAF sites from late tonight to early morning near dawn at
Mcallen, and will continue through Brownsville, maintaining
unsettled, and likely MVFR, conditions through late morning.
.PREV DISCUSSION... /issued 433 PM CDT MON MAY 30 2016/
SHORT TERM (Tonight through Tuesday Night): The conv that fired
up along the conv outflow moving in from our north has died out
or moved south of the Rio Grande this afternoon. This indicates
that the atms over the RGV has stabilized for this evening and
conv should be pretty minimal at least into the early evening.
Further northwest...radar data indicates that additional conv has
fired up over the Big Bend area of the Rio Grande. The latest
HRRR guidance keeps the RGV generally rain free through most of
the night with conv remaining concentrated over the higher terrain
of northeast Mexico. This scenario looks reasonable considering
that the atms has stabilized and we will be losing the daytime
heating in a few hours. Will mention the chance for some lingering
conv into the early evening hours. Then will mention only a slgt
chc over the western counties to account for any conv that may
persist and move off of the higher terrain of Mexico.
Further down the road...the 500 mb closed low over AZ will drift
SE into NW Mexico by Tues night. Pockets of PV will periodically
move around the south side of the closed low pushing over South
TX Tues and Tues night. The main question will be how much will
the atms destabilize and moisten up through Tues and Tues night.
The 12z BRO sounding shows a good MUCAPE of 3443 J/KG with a so-so
PWAT of around 1.7 inches. NAM and GFS hold off on advecting in
significant moisture values through the short term with the ECMWF
being the most aggressive in moisten up the atms. So accordingly
the ECMWF is much quicker in bringing in higher pops through the
short term especially out west with the NAM and GFS being much
more conservative for the rain chcs. Will maintain chc pops out
west for Tues/Tues night with keeping more slgt chc across the
eastern counties as the ECMWF may be overdoing how quickly the
atms will destabilize. Overall confidence is not too great here
considering the model disagreement.
Will go closer to a blend of the NAM and GFS MOS temps throughout
the short term since the ECMWF numbers are a bit cooler due to the
higher pops. Once again confidence is only average here.
LONG TERM (Wednesday through Monday): The forecast period begins
with a pair of 500mb lows, one low/trough across arizona into
northern Mexico and another low over the northern plains. The mid
level low over the Dakotas will move east into the upper Midwest
region by late week. The mid level low across southern New Mexico
into northern Mexico opens up and moves over the Big Bend region
Wednesday night into Thursday. Moisture beings to pool ahead of a
late season weak cold front which is expected to move into the
central Texas by Thursday.
Showers and thunderstorms will develop across portions of Deep South
Texas Wednesday into Thursday as the 500mb low approaches. A weak
cold front approaching from the north will allow moisture to pool
along and ahead of the frontal boundary. Rain chances will increase
across the region Wednesday into Thursday and remain high into
Friday as broad low pressure develops across the stalled frontal
boundary across the area.
The GFS and ECMWF models are in pretty good agreement in the timing
and placement of the mid level features through late week with some
differences into the weekend. The mid level low is forecast to
meander across portions of central and south texas Friday into
Saturday. If this verifies, considerable amount of rainfall is
possible across portions of Deep South Texas through the rest of the
week into the weekend. Flash flood watches may be needed for the CWA
through the rest of the forecast period if the upper level system
lingers across central or south Texas Saturday into Sunday as
indicated by the latest models. Temperatures expected to remain near
or slightly below normal due to the increase in cloud cover and rain
MARINE: /Tonight through Tuesday night/...The AZ 500 mb closed
low moving across the U.S./Mexico border region will strengthen
the surface troffing across the southern Plains states. This will
increase the the PGF to near SCEC criteria throughout the short
term period. Brief SCA conditions could occur mainly over the Gulf
waters at night. But do not expect extended SCA conditions at this
Wednesday through Saturday...Moderate to strong southeast winds will
prevail along the lower Texas coast Wednesday into Wednesday night.
The pressure gradient weakens across the western Gulf of Mexico
Thursday and Friday as a weak cold front moves into the area. Light
to moderate southeast winds expected across the coastal waters
Thursday through Saturday as a result.
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