Area Forecast Discussion
Issued by NWS Brownsville, TX
FXUS64 KBRO 300548
Area Forecast Discussion
National Weather Service BROWNSVILLE TX
1248 AM CDT MON MAY 30 2016
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...The weather conditions will be very similar to
the previous 24 hours across Deep South Texas with a light
SE wind prevailing through the night. VFR conditions will
transition into MVFR early in the morning with CIGS around
1500 to 1800 feet. The gradient will be much weaker during
the daytime hours tomorrow allowing for moderate SE winds
developing in the afternoon and the return of VFR conditions.
.PREV DISCUSSION... /issued 619 PM CDT SUN MAY 29 2016/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...next 24 hour TAF period looks to more or less be a
repeat of the past 24 hours. Will begin period with winds
generally in the 16 to 24 kt range before diminishing to less than
12 kts around 03Z where they will remain through around 15Z Monday
morning. VFR cigs/vis to prevail through at least 06Z when MVFR
cigs will begin to develop area-wide. After 15Z Monday morning,
winds will rise into the 12 to 20 kt range then into the 16 to 24
kt range after 19Z or so. MVFR cigs will generally hang around
through mid to late morning before beginning to break up and
become VFR once again around the midday Monday time frame.
PREV DISCUSSION... /issued 308 PM CDT SUN MAY 29 2016/
SHORT TERM (Tonight through Monday Night): A 500 mb trough over
the southern Cali coastline will push east through Mon and Mon
night. Several pockets of good PV will be moving around the base of
the trough axis ejecting out over the south central Plains state
through the short term increasing some divergence aloft. The main
question for conv though will be moisture and instability. The 00z
BRO sounding shows good CAPE values in place over the RGV with an
MUCAPE of 3798 j/kg but with a pretty dry PWAT of 1.5 inches. The
latest NAM/GFS and ECMWF model runs show a fairly narrow band of
deeper layer moisture forming up over northeast Mexico and edging
into the far western portions of the BRO CWA through Mon night.
Expect the main threat for any pcpn over the region will be the
western counties where some of the conv that could fire up to the
north and west of the CWA could edge into the western areas where
some better moisture and instability values reside. So will maintain
the slgt chc pops here with single digit pops elsewhere through
SPC is keeping the best potential for svr conv well to the northwest
of the BRO CWA due to the more limited deep layer moisture in place
over the area. Although some stronger conv could wander into the
western counties from the higher terrain of Mexico...do not expect
this to be very long lived.
The NAM/GFS and ECMWF numerical guidance for both temps and pops are
in pretty close agreement for values through tomorrow night and will
go pretty close to a blend of these for values for the short term.
MAV and MET guidance for the northern counties indicates some
potential for some light fog late tonight through Mon morning and
will mention this in the forecast for tonight.
LONG TERM (Tuesday through Sunday): The forecast period begins
with a weak 500mb ridge over texas, a 500mb low/trough across
Arizona and a 500mb low/trough over the northern plains. The mid
level low over the Dakotas will move east into the upper Midwest
region by midweek. The mid level low across Arizona into northern
Mexico opens up and moves into the south central Plains states
Wednesday night into Thursday. A late season weak cold front is
expected to move into the central Texas on Thursday.
The latest GFS and ECMWF models are in pretty good agreement in the
timing and placement of the mid level features through late week.
However, the ECMWF is wetter with better moisture advection across
the region and a strong upper level impulse moving overhead on
Wednesday. Also, the models differ on the timing and placement of
the 500mb low across Texas by the weekend.
Daytime heating, ample moisture and impulses in the southwest flow
aloft will support showers and thunderstorms each afternoon and
evening (especially across the western areas). Rain chances steadily
increase mid to late week as a late season weak cold front
approaches the area. Showers and thunderstorms will develop along
and ahead of this frontal boundary as it continues to move southward
into Deep South Texas Thursday as moisture continues to pool along
the front. Rain chances linger into the weekend as the 500mb
meanders across or just east of the region. Temperatures expected to
remain near or slightly below normal due to the increase in cloud
cover and rain chances.
MARINE: /Tonight through Monday Night/...The west coast 500
mb troffing moving towards the central plains states will strengthen
the surface troffing. 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 overall
confidence is not strong enough to post an SCA at this time.
Tuesday through Thursday night...Moderate to strong southeast
winds will prevail along the lower Texas coast Tuesday into
Wednesday. The pressure gradient weakens across the western Gulf
of Mexico Wednesday night into Thursday as a weak cold front moves
into area. Light to moderate southeast winds expected across the
coastal waters Wed. night into Thursday as a result.
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