Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Brownsville Texas
621 PM CST Thursday Jan 29 2015
Discussion...updated for latest aviation discussion below.
Aviation...VFR conditions will prevail across deep south Texas
through this evening. Wind speeds will gradually decrease tonight as
a weak front approaches from the north. Light winds overnight may
allow fog to develop across the area...mainly after 07z. Fog will
lift by 14z as drier air and stronger winds filter into the region.
Rain chances will remain fairly limited with the frontal passage.
Low cloud decks will remain across the area on Friday. Some of the
latest model data suggest that MVFR ceilings are possible late
Friday morning into Friday afternoon. Will mention ceilings around
3500 feet in the wake of the front...however ceilings may need to be
adjusted downward to MVFR levels.
Previous discussion... /issued 246 PM CST Thursday Jan 29 2015/
pronounced middle and upper level ridging is slowly amplifying over
northern Mexico and the southwestern US. In response...surface
high pressure is strengthening over the Western Plains and a weak
cold front on the leading edge of that airmass is slowly making
its way through central Texas. Locally modest low level moisture
is in place giving way to much drier air from 900mb and up with
moderate southeast winds driven by northeast Florida centered high
Tonight...a weak cold front will approach from the north...likely
reaching close to the Falfurrias/Hebbronville area by daybreak. Wind
speeds will diminish as the low level gradient relaxes ahead of the
front. Middle level cloudiness will begin moving in this evening and
that may work to limit radiational cooling enough to prevent
dense/widespread fog formation but did include a mention of patchy
fog in the forecast for most of the area tonight.
Friday...cool front will sweep across the area through the day with
little fanfare. Wind direction will shift to the northeast at about
10 to 15 miles per hour and maximum temperatures will be about 10 degrees cooler
than today due to both advancing cool air and cloud cover limiting
daytime heating. Available moisture and lift appear limited however
and precipitation chances remain low and amounts likely even lower even
where rain occurs.
Friday night...surface winds will transition back to the southeast
as troughing builds over northwestern Mexico. Low level moisture
will also begin to slowly filter back into the region but it will
likely be low enough and wind speeds high enough to prevent fog
formation. Very modest warm air ascent may spark a few sprinkles or
showers in the western zones and left a slight chance of showers in
the forecast there. /68-jgg/
Long term /Saturday through Wednesday/...the long term models
seem in reasonable agreement through about Tuesday...when some
differences arise. The European model (ecmwf) kicks an ejecting low latitude cutoff
low through the area more quickly...with drier air arriving
Wednesday as opposed to the GFS...which delays passage of the
upper feature another 12 hours...through late Wednesday. After a
Monday night with low temperatures mainly in the 40s...temperatures will
slowly modify/recover...but won't reach normal territory again
Meantime...old man winter is being slow to loosen his grip as an
Arctic source air mass moves south across the plains to arrive
across the County Warning Area Sunday night. High temperatures in the 70s will turn into
a struggle to get out of the 50s on Monday...with robust chances
of overrunning light rain Monday through part of Wednesday.
Another shot of northern air will arrive Wednesday night into
Thursday with additional light rain chances and a weak reversal of
slightly increasing high temperatures for a day on Thursday.
now through Friday night... very favorable marine conditions are
expected through this evening and tonight with low to moderate
seas. Areas of patchy fog may form late tonight near Padre Island.
Northeasterly winds will increase during the day tomorrow but are
currently forecast to remain below exercise caution levels and the
strongest winds will likely remain north of Port Mansfield.
Moderate winds are expected to then shift to the southeast through
Friday night with seas remaining moderate.
Saturday through Monday...middle level ridging overhead Saturday
morning will support high pressure downstream and a light to
moderate southeast wind Saturday morning through Sunday...
decreasing slightly Saturday night and Sunday. Offshore wave
heights will start out at 4 to 5 feet...and will lower to 3 feet
on Sunday. The influx of strong high pressure Sunday night will
result in deteriorating marine conditions after midnight. Strong
north winds gusting to 30 kts will build seas Monday resulting in
Small Craft Advisory conditions for the day.
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