Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 160905

Area Forecast Discussion
National Weather Service Brownsville TX
405 AM CDT Sun May 16 2021

.SHORT TERM (Today through Monday): Deep South TX and the RGV is
positioned between two conv areas. The first is a conv complex well
south of the RGV while the other area is some spotty conv firing NW
of the region over north central Mex. The isold cell west of Zapata
CO has been steadily weakening as it pushes SE. This is due to the
isold conv moving into much lower surface based CAPE values
indicated by the LAPS data. These areas of lower CAPE will tend to
inhibit the conv development in the short term. However, higher CAPE
values are located mainly over the immediate Gulf waters just
offshore. As the daytime heating increases, expect the inland CAPE
values will start increasing which will in turn allow for some
additional isold/sct conv during the late morning and afternoon
hours. The conv potential for the RGV will be helped along today as
some weak areas of 500 mb vorticity eject eastward from the large
closed 500 mb low centered over the Desert SW.

Later today and tonight, short term model guidance start bringing in
drier and more stable air into the region from the west as the 500
mb closed low over the Desert Sw pushes into New Mex and West TX
by Mon Night. Accordingly, expect the RGV to have one more shot at
some isold/sct conv today and tonight followed by lowering pops
into Mon.

The NAM and ECMWF are in better agreement for pops through Mon
with the GFS coming in quite a bit drier and more stable today.
Since the GFS is the outlier for temps/pops, will lean towards the
NAM/ECMWF blend for the short term.

The latest Day 1 conv outlook from SPC continues to place Deep South
TS in the Marginal Svr Wx Outlook with some large hail and damaging
wind gusts being the main svr wx threat for today. Since a 60 mph
wind gust was reported at the Edinburg AWOS yesterday afternoon,
will continue to mention the potential for an isold strong/svr
thunderstorm in the upcoming HWO product for the RGV.

.LONG TERM (Monday Night through Saturday): A 500mb low/trough over
the Four Corners region Monday night will slowly move into Texas by
midweek. The pressure gradient is expected to strengthen across the
area Monday night into Tuesday as surface low pressure develops
across the Southern Plains. This will result in breezy conditions
near the coast Monday night and Tuesday. Tuesday will be very warm
to hot as weak ridging remains briefly overhead. The 500mb trough
swings into Texas Wednesday and lingers into Thursday. The
combination of deep moisture, PWATS of 1.8 to 2.2", in place and
the approaching trough axis will support scattered to numerous
showers and thunderstorms across deep south Texas Wednesday and
Wednesday night. High QPF values are forecast with this system and
heavy rainfall will be possible with nuisance flooding Wednesday
into Wednesday night. A general weakness aloft will maintain rain
chances Thursday into Friday before mid-level ridging builds back
into the region. Temperatures are expected to fall to near normal
mid to late week due to increase rain chances and cloud cover.


.MARINE (Today through Monday):  An ASCAT satl pass occurred along
the lower and mid TX coastlines at 0430Z last night and reflected an
E-SE surface flow over the region at 10 to 15 kts generally
offshore. This tends to support SCEC conditions for both the Bay and
Gulf Waters today. The PGF then weakens a bit later tonight into Mon
allowing for a little lower winds and seas. So no solid SCA
conditions expected throughout the short term. Areas of conv moving
offshore may temporarily boost up the winds and seas due to conv
winds and will handle these with SMW/MWSs.

Monday Night through Thursday: Moderate to occasionally strong
southeasterly flow is expected to prevail through much of the
period. The pressure gradient will strengthen along the lower Texas
coast on Monday night into Tuesday as low pressure develops across
the Southern Plains. Small Craft Exercise Caution to low end Small
Craft Advisory conditions are expected through the period. Showers
and thunderstorms will return Wednesday into Thursday.


BAYVIEW/PORT ISABEL  85  75  85  77 /  50  20   0   0
BROWNSVILLE          87  76  90  78 /  50  20   0   0
HARLINGEN            88  75  91  77 /  50  20   0   0
MCALLEN              90  75  93  77 /  50  20   0  10
RIO GRANDE CITY      94  74  98  76 /  50  10   0  10
SOUTH PADRE ISLAND   80  77  81  77 /  50  20   0   0




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