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Area forecast discussion...updated
National Weather Service Brownsville Texas
552 am CST sun Dec 8 2019

Discussion...updated for latest aviation discussion below.

&&

Aviation...radiational fog was able to materialize across deep
south Texas overnight with visibilities down to LIFR levels at
hrl and periodically at bro. Mfe has been generally ranging from
IFR to MVFR conditions. Fog will linger through about 15z before
eroding with daytime heating. VFR conditions should prevail once
the fog ends with moderate southerly breezes developing by the
afternoon. The southerly breezes continue into Monday night, which
should help diminish the potential for fog overnight. However, it
could not be ruled out for fog across the northern and western
ranchlands where winds will remain the lightest.

&&

Previous discussion... /issued 443 am CST sun Dec 8 2019/

Short term (now through monday): with clear skies and light winds
across the region, temperatures dropped overnight down into the 50s
areawide except along the immediate coast. These slightly cooler
than originally forecasted temperatures have dropped closer to the
area dew points and has led to pockets of dense radiational fog
across portions of the area, especially across the northern
ranchlands. A dense fog advisory is in effect for portions of the
region through 9 am CST as a result. Once the fog erodes in the
morning, anticipate a mild day under mostly sunny to partly cloudy
skies with afternoon highs in the low 80s for most with modest
southerly winds.

Late tonight into Monday morning remains mild and more humid as a
result of the increasing onshore southerly flow, especially near the
coast, as the pressure gradient strengthens with a developing low
pressure system across the central US. However, cannot rule out the
potential for some fog, especially to the north and west, where
winds will remain the lightest. With the tighter pressure gradient,
breezy conditions will be expected across portions of the lower to
Mid-Valley and along the coast. These southerly winds are to also
promote well above average temperatures featuring afternoon highs
reaching into the mid to upper 80s across the inland portions of
deep south Texas under mostly sunny to partly cloudy skies.

Long term (monday night through saturday): as a 500 mb shortwave
swings eastward across the Desert Southwest and into Texas Monday
evening, a strong cold front will approach deep south Texas.
Models are in good agreement with bringing the front through
Tuesday morning and have it reach the Rio Grande Valley by mid
morning. The GFS is lagging behind slightly, but decided to lean
towards the timing of the NAM and ecm solutions. The maximum
temperature on Tuesday will likely be in the early morning hours
immediately preceding the frontal passage and then temperatures
will fall throughout the day and into Tuesday night, dropping into
the 40s and possibly the upper 30s along our northern border by
Wednesday morning. Strong northerly winds will accompany the
frontal passage, and a Wind Advisory may be needed, primarily for
along the coast and possibly for the western counties. Rain
chances increase along and ahead of the front and then clear out
as drier air is ushered into the region late Tuesday night into
Wednesday.

Mid level ridging temporarily builds in behind the front on
Wednesday before another 500 mb shortwave trough swings across Texas
Thursday night. The GFS has the shortwave dig in deeper over deep
south Texas and brings in more 1000-500 mb moisture. For now, have
decided to split the difference and put in slight chance pops on
Friday for the eastern portion of the County Warning Area along with offshore.
Temperatures are expected to gradually increase each day behind the
front, with highs in the lower 60s on Wednesday, dropping into the
40s again Wednesday night, then reach the mid to upper 60s on
Thursday. Heading into the weekend, a broad 500 mb high flattens and
moves in behind the shortwave, suppressing any pops, causing winds
to shift out of the south, and allowing temperatures to increase
each day.

Marine (now through monday): marine conditions will continue to
remain favorable into this afternoon before south-southeasterly
winds start to gradually strengthen late Sunday afternoon into
Monday as a result of a tightening pressure gradient. Seas will
slowly build as well. The southerly winds become quite breezy
Monday with moderately building seas. Small craft exercise
caution to Small Craft Advisory conditions are expected.

Monday night through Friday...scec conditions will be likely
Monday evening with strong southerly winds on the Lower Texas
coastal Gulf waters. After a temporary reduction in wind speeds
early Tuesday morning, a strong cold front will advance across the
waters late Tuesday morning. Conditions will rapidly deteriorate
behind the passage of the front with likely gale-force wind gusts
for a period of time. Hazardous marine conditions will continue
into Wednesday before improving to moderate levels Thursday and
Friday as winds and seas gradually subside.

&&

Bro watches/warnings/advisories...
Texas...dense fog advisory until 9 am CST this morning for txz249>251-
254>256-351-353.

GM...none.
&&

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