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000
FXUS64 KBRO 191847
AFDBRO

Area Forecast Discussion
National Weather Service Brownsville TX
147 PM CDT Fri Apr 19 2024

...New SHORT TERM, LONG TERM, MARINE...

.SHORT TERM...
(Tonight through Saturday night)
Issued at 147 PM CDT Fri Apr 19 2024

Quasi-zonal 500mb flow over the southern tier of the CONUS with
embedded shortwaves to provide western and northern portions of Deep
South Texas a slight chance of rain tonight and Saturday. A better
chance for showers and thunderstorms for all areas are expected
Saturday night will be associated with a slow moving cold front.

18Z surface analysis shows the cold front extending from Eastern
Texas through the Texas Hill Country to near Del Rio. Models
indicate a slow southerly drift the next 24 hours due to zonal flow
aloft and weak surface ridging over the Central Plains. In advance
of the front, a weak shortwave is shown mainly by the GFS crossing
over the Sierra Madre later tonight igniting a few clusters of
thunderstorms over NE Mexico. The westerly flow aloft may allow for
a few thunderstorms to cross the Rio Grande possibly impacting
Zapata, Starr and Jim Hogg Counties. Brief moderate to heavy
rainfall, gusty winds and occasional lightning strikes will
accompany any of these storms. For the RGV, low level capping
inversion will be in place so not expecting these storms to hold
together as they drift eastward.  Otherwise, low clouds increase
overnight with temperatures only lowering into the low to mid 70s.

The front begins to move south later Saturday and advances through
the our region Saturday night as high pressure drops south behind a
northern stream low pressure trough.  Daytime Saturday is expected
to be cloudy to mostly cloudy, warm and humid. Highs climb well into
the 80s to lower 90s even with all the cloud cover. As for shower
and thunderstorm chances expect isolated activity at best Saturday
morning with the departing initial shortwave and slight chances for
the afternoon mainly due to daytime heating. Models and ongoing
forecast ramps up rain chances Saturday evening and night as the
cold front advances through the region.  Model consensus PoPs have
increased chances into the 30-70% range with highest probabilities
over the northern and western ranchlands. As for strength of these
potential thunderstorms, latest high resolution models show a
weakening capping inversion with ML CAPE in the 1500-2000 j/kg range
and 0-6km shear values 30-35 kts. These values may be sufficient for
a few strong to borderline severe storms. At this time, SPC
indicates only general thunderstorms over Deep South Texas with a
Marginal Risk (1 out of 5) for severe thunderstorms over
Southcentral and Southeast Texas.  As for rainfall amounts,
precipitable water values of near 1.8 inches (>90% percentile)
should be sufficient for one-half to one inch amounts from any
thunderstorm and can not rule out 2 inches in slow moving storms.

&&

.LONG TERM...
(Sunday through next Friday)
Issued at 147 PM CDT Fri Apr 19 2024

By the start of the long term period, the cold front is expected
to have moved across Deep South Texas and the Gulf waters.
Northerly winds will increase through the morning hours, with the
breeziest winds expected over the Gulf waters and along the
immediate coast. Wind gusts around 20-30 MPH will prevail through
the day, but should begin to subside late Sunday evening. The
latest guidance indicates portions of Deep South Texas, mainly the
Rio Grande Valley, will still see scattered showers and isolated
thunderstorms through late Sunday morning. High temperatures will
be noticeable cooler, ranging from the 70s across the Northern
Ranchlands to around 80 degrees across the Lower RGV.

Monday will be the coolest day of the week as the region remains
under the influence of surface high pressure, with morning low
temperatures in upper 50s to low 60s and afternoon high
temperatures in the 70s. However, this brief cool down will be
short-lived. As surface high pressure shifts east through mid
week, surface winds will return to the east and southeast and
result in the start of a warming trend once again. An uptick in
wind speeds is expected by mid week in response to a deepening
system traversing the Plains. Temperatures will gradually warm
each day, with highs in the upper 80s and low 90s expected by
Thursday across Deep South Texas.

&&

.AVIATION...
(18Z TAFS)
Issued at 1222 PM CDT Fri Apr 19 2024

Ceilings will continue to gradually rise with occasional breaks in
the BKN-OVC skies through the afternoon. Ceilings are expected to
rise in the VFR levels with a few bases between 25-30kft. Ceilings
are forecast to lower rapidly this evening and overnight with high
to moderate 60-90% probability of IFR. These lower conditions to
persist through at least 15Z Saturday with a steady rise
thereafter. Light to moderate southeast winds to prevail with
gusts in the 15-20kt range at times.

&&

.MARINE...
Issued at 147 PM CDT Fri Apr 19 2024

Tonight through Saturday night...Through Saturday a light to
moderate southeast to east flow with a slight to moderate sea is
expected with a slow moving cold front across Southcentral Texas.
The front is on track to move into coastal waters late Saturday
night with an initial line of showers and thunderstorms followed
by fresh to strong northerly winds by sunrise Sunday. Small Craft
Advisories are likely to be issued in wake of the frontal passage.

Sunday through Friday...The passage of a cold front will result
in increasing northerly winds and building seas on Sunday and
Sunday night. Small Craft Exercise Caution conditions are likely,
with a low potential for Small Craft Advisory conditions. More
favorable conditions are expected beginning on Monday and
continuing through the end of the week. Winds will shift to the
east and southeast on Monday, with southeast winds prevailing
Tuesday through Friday.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             74  88  71  79 /   0  10  30  50
HARLINGEN               71  90  67  78 /   0  10  30  40
MCALLEN                 74  92  68  78 /  10  10  40  50
RIO GRANDE CITY         73  93  65  75 /  10  10  50  50
SOUTH PADRE ISLAND      74  81  71  76 /   0   0  20  50
BAYVIEW/PORT ISABEL     72  85  69  78 /   0  10  20  40

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&

$$

SHORT TERM...59-GB
LONG TERM....22-Garcia
AVIATION...59-GB