Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 192338 AAA

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
638 PM CDT Tue Sep 19 2017

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

.AVIATION...Only minor cosmetic changes to the previous set of
TAFs. VFR to MVFR is anticipated overnight with lowered clouds,
streamer showers, and/or light fog. Full VFR should return on
Wednesday with seabreeze convection possible with higher clouds.

.PREV DISCUSSION... /issued 307 PM CDT Tue Sep 19 2017/

SHORT TERM (Tonight through Wednesday Night): In short, the hot and
humid conditions and low chance of rain is expected through the
short term with little change from the last few days. Morning
sounding indicated a rich tropical airmass in place over Deep South
but at limited depth. Precipitable waters values at 2.2 inches(12Z
Sounding) should remain between 2-2.25 inches through tomorrow with
a steady influx of gulf moisture around the surface high extending
across the Gulf of Mexico. The abundant low level moisture, AOB
700mb, is sufficient for continued diurnal a slight chance of
showers/thunderstorms but the persistent 500mb ridge and elevated
drier air to keep a cap on any significant increase in convection
the next 36 hours. Model guidance confirms this keeping pops between
10-20 percent and favoring areas along and east of I 69C.
Temperatures to remain above normal with the mid level ridge in
place with heat indices well above normal due to the higher then
normal dew points.

LONG TERM (Thursday through Tuesday): General synoptic flow
across the Southern Plains and into Deep South Texas will be
dominated by mid-level ridging with a deep trough digging into the
western U.S. and troughing across the Northeast U.S., in part due
to Hurricane Jose just off the coast. Limited moisture through the
end of the week will likely keep PoPs isolated diurnally with
possibly scattered nocturnal precipitation over the marine areas
as a weak mid-level low develops over the Central Gulf by the end
of the week. Models indicate a Rex Block pattern this weekend with
low pressure over the Gulf and stronger high pressure positioned
across the Midwest and Great Lakes through Monday. We will remain
on the more subsident side of the low this weekend with abundant
dry air above 850mb keeping precipitation chances low. However,
with relatively light east/southeast flow at the surface, diurnal
seabreeze convection will be possible each day. Going into early
next week towards the end of the forecast period, precipitation
chances may increase as the deep trough over the desert southwest
slowly moves eastward and moisture increases. Temperatures each
day will continue to be a few degrees above normal through this
weekend with highs in the mid to upper 90s for most areas.

MARINE (Tonight through Wednesday night): A persistent light
southeast wind and low sea is expected through Wednesday with a
weak surface high extending east to west over the Gulf of Mexico.
the moisture southeast flow will maintain a slight chance of
showers or isolated thunderstorms. No small craft advisories are

Thursday through Tuesday: Light to moderate surface winds will
continue across the coastal waters through much of the long term
period with seas generally at 2 to 4 feet in the Gulf waters. A
slight chance of showers and thunderstorms is possible each day
through early next week.



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