Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 230723 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
223 AM CDT Sat Sep 23 2017

.DISCUSSION...Updated for latest aviation discussion below.


.AVIATION...IR Satl imagery early this morning shows only some sct
clds over the region with KBRO radar indicating only some isold
conv firing over Kenedy County moving northwest. Daytime heating
in combination with the afternoon sea breeze may result in some
more sct conv along with lower ceilings. This may result in some
MVFR ceilings this afternoon and early this evening. However
expect overall VFR conditions to prevail for the RGV TAF sites.


.PREV DISCUSSION... /issued 703 PM CDT Fri Sep 22 2017/

DISCUSSION...Updated for latest aviation discussion below.

AVIATION...Satellite and radar images as well as surface
observations indicate convection across central and northwest
portions of the CWA early this evening. Ceilings were near 4400ft
at KEBG to near 5500ft at KHBV. Expect VFR conditions to prevail
across the Rio Grande valley and northern ranchlands the rest of
tonight into early Sat morning as weak 500mb ridging across south
Texas provides subsidence across the area.

PREV DISCUSSION... /issued 334 PM CDT Fri Sep 22 2017/
SHORT TERM (Now through Saturday Night): Another round of
convection has developed along the coastal counties this
afternoon, mostly aided by a seabreeze. Additional development is
initiating across the Upper Valley and Ranchlands as low-level
lapse rates are fairly steep per model sounding data, so have
increased PoPs slightly out west through 00Z this evening.
Precipitable Water values still remain near or above 2" today, so
any showers and storms will be able to produce locally heavy
rainfall and lead to nuisance flooding of urban and low-lying

Tonight, convection should decrease shortly after sunset as the
mid-level pattern remains fairly unsupportive of continuing
activity with the ridge axis overhead through the Midwest and loss
of daytime heating. Isolated PoPs do remain in the forecast,
however, with RH values above 60% from the surface through near
500mb. On Saturday, expect more of a seabreeze influence with a
more easterly component in the surface winds, so isolated to
scattered showers and storms are expected again through the
afternoon. Winds will be a bit lighter with above-normal
temperatures in the upper 90s to near 100F Saturday afternoon.

LONG TERM (Sunday through Friday): The weather pattern will
continue to evolve through the long term with improving
conditions for widespread rainfall and slightly lower temperatures
at least for maximum temperatures. Deep South Texas will be on
the western side of a mid-level ridge over the Central Gulf and a
deep upper level trough over the Rockies and the Desert SW. At
the surface, a cold front is expected to move into north central
Texas around Tuesday and slowly work its way south possibly
through the RGV Friday. Tropical moisture from the Pacific and
Southern Gulf of Mexico is expected to deepen in advance of the
above mentioned trough and surface cold front with heavy rainfall
potential becoming a real possibility with pwats exceeding the 90
percentile and nearing record levels for late September. Models
suggest the cold front will work its way through Deep South Texas
late next week but with little to no decrease in moisture content
keeping rain chances at least in the moderate range next Friday
and Saturday allowing for temperatures to lower to at least near
normal. Overnight lows will remain well above seasonal normal
with plenty of cloud cover and high dew point temperatures. Latest
MEX/ECM guidance numbers are in fair agreement and consistency
and work well with the inherited pops and temps.

MARINE (Now through Saturday night): Surface high pressure over
the northeast Gulf will continue to maintain light to moderate
east/southeast winds through the short term period with seas
generally at 2 to 4 feet. Scattered showers and thunderstorms will
also be expected with locally heavy rainfall possible.

Sunday through Wednesday: The light to moderate southeast flow
continues through much of the period with little change in
placement and strength of the surface pressure fields. A cold
front and lower pressure moves into North Texas around mid week
which might result in higher winds and seas but guidance keeps
conditions below small craft advisory levels at this time. Showers
and thunderstorms chances persist at 20-30 percent range over the
weekend with increasing chances next week as tropical moisture
increases in advance of the cold front.




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