Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 271141

Area Forecast Discussion
National Weather Service BROWNSVILLE TX
641 AM CDT Tue Sep 27 2016

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


.AVIATION...Complicated aviation forecast this morning with
showers currently moving in NE to SW from the Gulf and expected
to continue through the day, especially near the coast, due to a
surface trough/weak frontal boundary in the area. Expecting main
impacts at BRO and possibly HRL...with lesser rain chances inland
at MFE. Downpours are possible, mainly at BRO. Thunder cannot be
completely ruled out this afternoon, but instability is quite
limited, so will not mention in TAF`s. CIG`s have also been
falling to IFR (007-010) in showers this morning. Will carry SHRA
in TEMPO groups at BRO/HRL through 00Z then PROB30 until 06Z. Just
TEMPO at MFE this afternoon for now.


.PREV DISCUSSION... /issued 409 AM CDT Tue Sep 27 2016/

SHORT TERM (Today through Wednesday):
Locally heavy rainfall will still be possible, mainly along the
immediate coastal areas, over the next 24 hours as a coastal
trough/stalled frontal boundary remains in the area along with
copious moisture. Precipitable water values will be around 2.2
inches over the eastern CWA as NE surface flow continues to feed
in Gulf moisture. Recent HRRR runs indicating localized rainfall
of 2+ inches per hour in spots around daybreak today. This seems a
bit overdone, but did add heavy rain wording to weather for the
coastal counties through the day. WPC also keeping the SE CWA in a
marginal risk for excessive rainfall today...with areal average
precipitation amounts of 1-2" possible. MOS guidance also
supporting this possibility around the Brownsville area.

On the other hand...upper-level pattern not really conducive to
heavy rain production, as upper-level lows apparent on water-vapor
satellite imagery over Lake Superior, Baja California, and SE CONUS
leave much of Texas in area of general ridging aloft. Instability
will also be largely limited with light northerly flow and cloudy
skies expected today.  With all that said, basically going with WPC
QPF amounts but not confident enough to issue a Flash Flood Watch at
this time.  Of course need to monitor the situation.  PoP and QPF
totals fall off quickly further inland.

Daytime max temperatures on Tuesday will run 4-5 degrees below
normal with cloud cover and northerly flow in place.

Overnight Tuesday into Wednesday, an upper-level ridge amplifies
upstream of the area ahead of the old low over the SW CONUS. Column
moisture stays fairly high, though, especially along the coast, so
rain chances continue there overnight.  Min temps range from the mid-
70s along the Gulf to perhaps the upper 60`s in Zapata county.

On Wednesday, column RH finally starts to decrease a bit as flow
aloft becomes more northerly.  Some signal in the models that winds
will turn NE again during the day though...bringing increased rain
chances to (you guessed it) the SE part of the CWA including
Brownsville.  Not especially confident in this yet, but something
for later shifts to keep an eye on.

LONG TERM (Wednesday Night through Monday): The H5 ridge will be
more dominant through the period, deflecting weather systems away
from the region. The remnants of the cold front/coastal trough
will still be lurking near the lower valley and offshore by
Thursday morning, but reinforcing high pressure will be surging
southward across Texas during the day. Will hold on to isolated
shower forecast for the lower valley due to just enough remaining
moisture and surface instability. Drier air surging into Deep
South Texas will finally clear things out Friday and for the
weekend. Will keep high temperatures close to consensus, reaching
the low to mid 90s. Dewpoints will be considerably lower over the
weekend, so the heat will not be as stifling as the past few

Now through Wednesday: Scattered showers and isolated
thunderstorms at times will be possible over the coastal waters
through the short-term. Heavy downpours are likely to occur in
some of the showers. Moderate NE winds today may approach SCEC
levels but should stay just below before falling to light-to-
moderate tonight and into Wednesday. Moderate seas of 2-4 ft. will
be the rule.

Wednesday night through Friday: Northeast flow will continue for
the marine zones through the rest of the week, with modest seas
continuing. A reinforcing arrival of high pressure will nudge
northeast flow back up to near 15 knots briefly on Thursday,
continuing to produce seas of 3 to 4 feet and a moderate chop on
the Laguna Madre.




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