Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 171720 AAB

Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
1120 AM CST Fri Jan 17 2020

...18z Aviation Update...

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


.AVIATION...VFR conditions will gradually deteriorate with time
later tonight. MVFR to IFR CIG and VIS can be expected by
Saturday morning just prior to sunrise. Little improvement is
anticipated from 12z through 18z Saturday, especially where
showers develop. Surface winds will remain light and variable
through the period.


PREV DISCUSSION... /issued 439 AM CST Fri Jan 17 2020/
SHORT TERM (Now through Saturday): Low to mid level moisture will
continue to increase across the state today as a 500mb trough
across the western United States moves eastward this afternoon.
Elevated convection currently across portions of northeast Mexico
early this morning and some of these showers will move into the
western portions of the CWA later this morning. Additional showers
will develop across northeast Mexico into southwest Texas tonight
as a weak 500mb shortwave trough moves across the area. Rain
chances will increase Saturday with a chance of thunderstorms as a
stronger shortwave trough moves across southwest Texas Sat
afternoon and a weak surface low pressure develops across the
upper Rio Grande Valley ahead of a cold front moving through south
Texas Sat afternoon. Will go with a blend of the NAM and GFS MOS
for temperatures today and tonight but will use a blend of
CONSALL/CONSRAW/CONSMOS for high temperatures Saturday.

LONG TERM (Saturday night through Thursday): The 500mb trough
axis will be well off to the east Saturday night with the
associated cold front clearing through Deep South Texas by Sunday
morning. Coastal troughing and deep-layer moisture will lead to
high rain chances early Sunday, especially across the Lower Rio
Grande Valley and marine areas before sunrise. Models indicate
precipitable water values may exceed 1.75 inches, which would
potentially be a daily record. Thus, locally heavy rainfall will
be possible with additional rainfall amounts ranging from a half
inch to an inch. As a strong surface high builds southward, the
gradient will relax and rainfall amounts will decrease from north
to south headed into early next week. Temperatures will be tricky,
which will depend on amount of cloud cover and ongoing shower or
thunderstorm activity. With the moderate to strong northerly flow
and expected rain shield, have lowered temperatures a few degrees
across the eastern areas on Sunday.

As onshore flow returns on Tuesday, temperatures will gradually
warm through mid-week to near normal on Wednesday and above normal
by the end of the week. The pattern becomes fairly progressive the
rest of the week with a series of shortwave troughs of low
pressure moving across the Southern Plains. The next disturbance
will move into the region on Wednesday, bringing an increase of
moisture and rain chances. This wave will be moving quickly, but a
few heavy downpours will be possible with moisture becoming very
deep. Another deeper trough may move across the state at the end
of the long term, but models diverge quite a bit at this point.

MARINE (Now through Saturday): Seas were near 3 feet with east to
southeast winds near 14 knots at buoy020 early this morning.
Moderate to strong southeast winds offshore this morning will
diminish in the afternoon as the pressure gradient weakens across
the western Gulf of Mexico with surface high pressure across the
eastern United States and a weak surface high across southwest
Texas. Will word SCEC across the offshore waters this morning as a
result. The pressure gradient will remain relatively weak across the
lower Texas coast tonight as a stationary frontal boundary across
the upper Texas coast weakens and a cold front moves into northwest
Texas. Light to moderate southeast winds will prevail across the
coastal waters tonight before increasing Saturday as low pressure
develops across the western portions of deep south Texas Sat
afternoon ahead of the cold front moving into south Texas. Moderate
to strong southeast winds will develop offshore the lower Texas
coast Sat afternoon to SCEC conditions.

Saturday night through Thursday: Hazardous marine conditions will
be likely as north winds increase and become strong behind a cold
front Saturday night into Sunday. Small Craft Advisories will be
likely and may persist into early Monday as coastal troughing
maintains strong northeast flow and elevated seas. Conditions may
briefly improve around mid week as high pressure builds and moves
off to the east. But, east to southeast flow is expected to
increase the rest of the week, which may keep seas at Small Craft
Advisory levels once again.




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