Area Forecast Discussion
Issued by NWS Brownsville, TX

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
000
FXUS64 KBRO 161134 AAA
AFDBRO

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
634 AM CDT Sat Mar 16 2024

...New AVIATION...

.SHORT TERM...
(Today through Sunday)
Issued at 135 AM CDT Sat Mar 16 2024

Ongoing severe thunderstorms across portions of the ranchlands
and brush country bringing hail and strong winds are beginning to
transition to a training heavy rain event across the ranchlands.
Some CAM guidance would continue thunderstorms this morning and
may redevelop during the afternoon, but the atmosphere may be a
little too worked over for that after daybreak. A repeat
performance is possible this evening into tonight, in generally
the same locations, potentially working further east and into the
Rio Grande Valley Saturday night with a little help from a passing
shortwave.

Regardless, a cold front and weak surface low meander in the
vicinity of the CWA border over the next 24 to 30 hours, with
abundant moisture, MUCAPE above 1500 J/kg increasing towards 3000
J/kg, bulk shear topping 35-40 kts increasing towards 50 kts by
the evening, and mid level lapse rates nearing 7.5 C/km, with
highs across the area topping the mid 80s. Once again, the set up
favors rotating updrafts with large hail and damaging winds as the
primary concerns.

The current Severe Thunderstorm Watch expires at 3 AM, and if
there is a rinse and repeat, we could see an additional watch
later Saturday for the same areas. SPC is carrying a Marginal Risk
for severe weather across most of the ranchlands and brush
country, with a Slight Risk across northern to central Zapata and
northwestern Jim Hogg counties. The Slight Risk area is also
hatched, indicating a higher probability of significant hail,
greater than 2 inches in diameter. WPC has posted a Marginal Risk
of excessive rainfall across portions of the ranchlands and brush
country as well today into early Sunday.

The front finally pushes through late Sunday morning, maybe Sunday
afternoon for the lower RGV. Temperatures still reach into the
80s, with the best cold air advection arriving into the long term
period. Finally, for those heading to the beach, expect a Moderate
Risk of rip currents and longshore currents, with an 8 second
swell period arriving by this afternoon and generally holding into
Sunday afternoon.

&&

.LONG TERM...
(Sunday night through Friday)
Issued at 135 AM CDT Sat Mar 16 2024

A cut-off low across the Desert Southwest and ridge across the
Pacific Northwest at 500mb hold in a Rex Block pattern into mid-
week, before the mid-level low finally wins out, trekking eastward
into the Southern Plains by the end of the week. This will
maintain a relatively active mid-level pattern across Deep South
Texas through Thursday, with a series of disturbances every 18
hours or so, holding southwest to nearly zonal mid-level flow in
between each shortwave. A reinforcing surge of high pressure,
stronger northerly flow, and cold air advection Monday keeps
temperatures below normal. Have nudged afternoon temperatures a
little lower Monday afternoon, mixing in some NAM guidance with
NBM. CAA continues into early Tuesday before winds turn easterly.
Southeasterly onshore flow returns Wednesday kicking highs back
toward normal, with above normal temperatures in the upper 80s to
low 90s returning Thursday and Friday.

Overall, the long term period may hopefully bring additional
beneficial rainfall to the CWA, with the best POPs toward the
brush country and Rio Grande basin. PWAT values through the period
persistently nudge above the 90th percentile (1.4 inches) for mid
to late March, to near 1.6 to 1.8 inches nearly every day into
Thursday.

Of course, the concern with this active pattern would be for any
isolated severe weather to continue again Sunday night, and mid
week, especially storms with large hail, running off the Mexican
plateau toward the borders of Zapata, Starr, and Hidalgo counties.
Isolated severe storms near the border can become quite common by
mid to late March. Overrunning showers or isolated thunderstorms
are possible Monday into Tuesday. Current QPF forecasts are
ranging from one quarter of an inch to one half inch through
Thursday, but with plenty of available moisture and multiple
chances for convection, a few locations may top 2-3 inches for the
week if they can catch a couple of storms.

&&

.AVIATION...
(12Z TAFS)
Issued at 631 AM CDT Sat Mar 16 2024

Convective activity has pushed offshore until probably this
evening or tonight. MVFR ceilings have given way to VFR conditions
so far this morning, with most model guidance building MVFR
ceilings back in this morning. Will optimistically hold the VFR
for now until this evening. AMDs or adjustments in future TAF
packages may need to be made. Expect easterly winds gradually
turning southeasterly into Sunday.

&&

.MARINE...
Issued at 135 AM CDT Sat Mar 16 2024

Today through Friday...A cold front eventually arrives across the
coastal waters Sunday, with a stronger northerly flow arriving
Monday as high pressure builds across the western Gulf of Mexico.
Small Craft Caution to Small Craft Advisory conditions are likely
Monday into Tuesday, with gusts to 30 kts across the bay or
nearshore Gulf waters possible. Winds turn easterly then
southeasterly into mid week, holding into the start of next
weekend, with generally favorable marine conditions. Showers and
thunderstorms are possible into Thursday, with gusty winds and
hail possible at times. Some patchy fog may also creep along the
coast before the front Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE             85  71  81  67 /  20  20  30  30
HARLINGEN               87  68  82  63 /  30  30  30  30
MCALLEN                 88  70  83  65 /  30  30  30  30
RIO GRANDE CITY         87  68  83  62 /  30  40  30  40
SOUTH PADRE ISLAND      75  69  75  66 /  20  10  20  20
BAYVIEW/PORT ISABEL     82  68  79  65 /  20  20  30  20

&&

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

$$

SHORT TERM...56-Hallman
LONG TERM....56-Hallman
AVIATION...56-Hallman


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.