Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 211949

Area Forecast Discussion
National Weather Service Brownsville TX
249 PM CDT Thu Mar 21 2019

.SHORT TERM (Tonight through Friday Night): Finally, sunshine has
broken out across the forecast area this afternoon as surface
high pressure (and ridging aloft) take shape across the region.
Unfortunately, as quickly as this high pressure developed, it will
move east over the next 24 hours or so. This should allow low
level return flow to increase. Clouds are expected to once again
develop as subtle impulses develop upstream across northern
Mexico. The larger shortwave will slide eastward across the
Rockies by Saturday.

Globals and mesoscale guidance are showing some QPF signal across
northern Mexico (near the Plateau). This looks to be orographic or
differential heating induced convection. The flow should bring what
is left across the western portions of the forecast area on Friday.
However, there is some uncertainty here as a strong EML is in place,
which would likely limit convection across the CWFA. Right now
expect mostly cloudy skies will keep us mostly in the upper 70s, but
that may be too low if clouds are thinner than expected.

.LONG TERM (Saturday through Thursday): The H5 trough moving
eastward out of the Four Corners region will be sweeping into the
central Plains. South Texas will be on the very edge of the
effects of this trough, with main impulses rotating around the
base of the trough Saturday morning. This will be the main period
of shower and thunderstorm threat for the region, with models
becoming more pessimistic on overall thunder activity in
successive runs. Models have most activity out of Deep South Texas
for the afternoon. Still cannot rule out a couple showers during
the main portion of our NWS Brownsville Weather Festival (10am to
4PM!), but they will be few and far between. Once the trough moves
to the northeast, midlevel flow will be buckling more from the
northwest, which is a drier signal for the region. The tail end of
a weak front tries to move into the region Monday, but more likely
is that a prefrontal trough will drift into the region from the
west, drying things our earlier, and bringing higher temperatures
during the day Monday. Have nudged temps upwards, especially out
west, into the mid to upper 80s, but this pattern has already
brought temperatures into the 90s earlier this season, so would
not be surprised to see that again. High pressure controls the
Gulf into Thursday, minimizing any rain chances, and keeping
temperatures in the 80s.


Tonight through Friday Night): Buoy 42020 is showing conditions
are MUCH improved across the adjacent coastal waters this
afternoon. Winds are generally less than 10 knots with seas
between 2 and 3 feet offshore. Tranquil marine conditions are
expected to continue through the short term marine period. There
is a bit of a signal for slightly higher winds and seas (wind wave
induced) as high pressure moves east of the region allowing for
southeasterly winds to increase. As southeast winds take shape,
can`t rule out some patchy marine fog toward the end of the
forecast period.

Saturday through Tuesday: Southeast winds continue into early next
week with high pressure dominating the Gulf. Gradient remains
modest, so winds will remain around 10 knots each day. Fetch
across the Gulf still considerable, so swells will remain 3 to 4
feet. A weak front drifts into the far northwest Gulf Monday
night, briefly switching winds to the northeast. Winds are
expected to remain light, so seas will be able to drop to around 2
feet through Tuesday.


BAYVIEW/PORT ISABEL  62  75  67  76 /   0  10  20  20
BROWNSVILLE          61  78  67  78 /   0  10  20  20
HARLINGEN            60  78  66  77 /   0  10  20  20
MCALLEN              61  79  66  79 /   0  10  20  30
RIO GRANDE CITY      61  78  66  80 /  10  10  20  30
SOUTH PADRE ISLAND   63  74  67  72 /   0  10  20  20




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