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Area Forecast Discussion (AFD)

Issued by Brownsville/Rio Grande Valley, TX (BRO)

FXUS64 KBRO 232110

Area Forecast Discussion
National Weather Service Brownsville TX
310 PM CST Fri Feb 23 2018

.SHORT TERM (Now through Saturday night): Skies continue to clear
across the western portions of the CWA and winds have increased 
across eastern portions where diurnal heating has allowed mixing to 
increase. The pressure gradient will be strong across the lower TX coast
tonight into Saturday and believe this will inhibit fog development
across most of the Rio Grande Valley tonight into Sat morning but
some patchy fog may develop across extreme western portions of 
the CWA Sat morning. May need a Wind Advisory for the coastal 
counties Saturday as a strong low level jet across the lower TX 
coast will mix down with diurnal heating late Sat morning. Breezy 
to windy will prevail across the Rio Grande valley Saturday before
a weak cold front moves into the northern ranchlands Sat night. 
Winds will diminish Sat night with scattered showers and isolated 
thunderstorms developing along the front late Sat night. Patchy 
fog will likely develop across portions of the Rio Grande valley 
late Sat night as well.

.LONG TERM (Sunday through Friday): A cold front will be moving
through the northern areas of the CWA at the beginning of the long
term period early Sunday. Models continue to bring it through Deep
South Texas late in the afternoon with increasing shower and
thunderstorm chances Sunday into early Monday. Timing of the FROPA
will be important and if it moves through around peak heating,
a few stronger storms will be a possibility. As of now, have kept
temperatures rising to near 80 in the lower Rio Grande Valley and
possibly several degrees higher around Brownsville or Harlingen.
12Z model soundings for Sunday afternoon show a moist and veering
profile with 0-6km shear increasing to 40 to 50 kts along with 
CAPE values of 1200 to 1500 J/kg, which may be enough for some
hail and strong winds.

As we go into early next week, coastal surface troughing will
continue to provide a decent chance of rain showers across the 
eastern half of the area, including the coastal and marine zones.
Temperatures will also range from the upper 60s to low 70s with 
possibly a higher warm-up out west with fewer clouds and showers 
expected. Southeast flow will return as the surface high shifts 
eastward and the next storm system develops in the Plains. 
Temperatures will rebound quickly Tuesday and Wednesday with winds
possibly exceeding Wind Advisory criteria on Wednesday as the 
pressure gradient strengthens. The next cold front will move 
through some time late Wednesday into Thursday, but model 
solutions diverge at this point. Went with more of a blend with 
the initial passage, but used the GFS for surface winds, which 
seem more realistic on Thursday when the better push of higher 
pressure comes. Towards the very end of the long term period, a 
coastal trough may develop post-front and bring another shot of 
cooler, wetter conditions for next weekend.


.MARINE (Now through Saturday night): Seas were 4 feet with
south to southeast winds near 12 knots offshore the lower Texas 
coast this afternoon. Moderate to strong southeast winds will 
prevail across the coastal waters tonight as low pressure across 
northwest Texas and surface high pressure across the eastern Gulf 
of Mexico provides a strong pressure gradient across the lower TX 
coast. Will continue to word SCEC for the far offshore waters. The
pressure gradient will remain strong across the western Gulf 
Saturday and moderate to strong south winds will prevail across 
the lower TX coast. A weak cold front will approach the coastal 
bend Sat night and winds will diminish as the pressure gradient 
weakens across the western Gulf. 

Marine fog will redevelop across the Laguna Madre and the nearshore 
waters tonight and Sat night as warm air moves across the cooler 
water temperatures. Some locally dense fog may develop across the 
lower TX coast reducing visibilities to less than a nautical mile.

Sunday through Friday: Light southeast flow will continue ahead of
the next cold front on Sunday evening, which will shift winds back
to the north and northeast into Monday. Shower and thunderstorm
chances will increase ahead of the front with a few stronger 
wind gusts possible Sunday night. A coastal trough will provide
light rain chances through Monday with east to southeast flow
returning Tuesday. Southeast flow will increase as the next storm
system in the Plains strengthens through mid-week with Small Craft
Advisories possible. Another cold front will move through 
sometime Wednesday night into Thursday. 


BAYVIEW/PORT ISABEL  70  84  69  77 /  10  10  20  50 
BROWNSVILLE          71  85  69  80 /  10  10  20  50 
HARLINGEN            71  86  69  78 /  10  10  30  50 
MCALLEN              71  87  68  75 /  10  10  50  50 
RIO GRANDE CITY      69  86  66  74 /  10  10  50  50 
SOUTH PADRE ISLAND   70  80  68  74 /  10  10  20  50 




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