Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 251119 AAA

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
619 AM CDT Sun Sep 25 2016

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

.AVIATION...Satellite and radar images and surface observations
indicate convection offshore the lower Texas coast this morning.
Mid to high level clouds were across the coastal sections of the
CWA as a result. Low to mid level moisture will continue to
increase across northeast Mexico into southwest Texas ahead of a
500mb low across northwest Mexico. Expect VFR conditions to
prevail across the Rio Grande valley and the northern ranchlands
today with showers in the vicinity developing late morning into
the afternoon. Brief MVFR may develop with isolated thunderstorms
this afternoon.

.PREV DISCUSSION... /issued 407 AM CDT Sun Sep 25 2016/
SHORT TERM (Today through Monday): A 500mb low will develop
across northwest Mexico today as the main energy associated with
the 500mb trough across the west- central United States moves into
the north- central U.S. this afternoon. At the surface...a weak
cold front will move across northwest TX today. Low to mid level
moisture will continue to stream northward across northeast Mexico
into west TX ahead of the developing 500mb low. Showers and
thunderstorms will continue to develop across portions of
southwest TX into west- central TX as well as across the northwest
Gulf of Mexico towards the coastal bend today. This will leave
most of the CWA in a donut hole with most of the rainfall to the
northwest and northeast of the area today through this evening.
Rain chances will increase across western portions of deep south
TX late tonight into Monday as the 500mb low across northwest
Mexico and the 500mb trough moving eastward across the north
central U.S. tonight bring the weak frontal boundary slowly
southward across central and south central TX. Will adjust pops
slightly higher west and slightly lower east tonight into Monday
and mention heavy rainfall with thunderstorms Monday as moisture
continues to pool along and ahead of the weak cold front across
south TX.

LONG TERM (Monday Night through Saturday):
Starting Monday night, the cold front will be finally arriving
across Deep South Texas, bringing along a substantial focusing
mechanism. Ample moisture will be available for the region, with
PW values well above 2 inches and no discernible dry air in the
column. This will bring about a continued very good chance for
rainfall Monday Night and Tuesday. With the moist sounding noted,
have added threat for heavy rainfall to the overall forecast. With
the front slowing considerably as it crosses the region, rain
chances will continue into Wednesday and Wednesday Night. Models
finally show some dry air aloft shifting in from the north
Thursday morning, which will let up on the rain chances,
especially for the northern ranchlands. This drier air will
continue to build and force moisture back to the south through the
rest of the week into the weekend, bringing an end to the rainfall
chances. Temperatures will be held in check considerably this
week, with highs not reaching the 90s Tuesday or Wednesday, and
only a slow recovery through the rest of the week.

Today through Monday...Seas were near 4 feet with south
winds near 18 knots at buoy020 early this morning. Moderate
southeast winds will prevail across the coastal waters today with
surface high pressure across the Gulf of Mexico and a weak cold
front moving through northwest Texas this afternoon. Scattered
showers and thunderstorms across the northwest Gulf of Mexico this
morning will continue to develop and move towards the coastal bend
but some of these showers and storms will move across the offshore
waters of the lower TX coast. Winds will back to the east to
southeast tonight and back to the east and diminish Monday as the
frontal boundary moves slowly southward across central TX tonight
and south-central TX Monday afternoon. Light to moderate east winds
will prevail across the western Gulf of Mexico on Monday as a
result. Periods of showers and thunderstorms will continue to
develop across the coastal waters today through Monday.



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