Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Brownsville Texas
1126 PM CST Tuesday Jan 27 2015
Discussion...updated for latest aviation discussion below.
Aviation...a few minor adjustments to the previous taf package.
Surface high pressure will continue to produce mainly VFR conditions
through the next 24 hours. Light winds overnight will become breezy
on Wednesday as the high pressure interacts with a low pressure
system moving into the Central Plains...with winds diminishing
beginning around sunset Wednesday evening. Ceilings are not
expected to be an issue through the forecast period.
Previous discussion... /issued 530 PM CST Tuesday Jan 27 2015/
Discussion...updated for latest aviation discussion below.
Aviation...minor adjustments to the previous set of tafs...
mainly to remove the thick cirrus forecast for tonight and
tomorrow and improve the visibility for overnight fog. High
pressure will provide light winds tonight that will become
breezy as low pressure moves into the Central Plains. VFR
is fully anticipated through a majority of the next 24 hours.
Previous discussion... /issued 246 PM CST Tuesday Jan 27 2015/
Short term /now through Wednesday night/...relatively benign
weather will prevail the next 36 hours under the dominance of broad
high pressure over the area. A bit of high cirrus is approaching
from over northwest Mexico and will increase over the currently
clear skies over the County Warning Area. Low temperatures tonight will be in the lower to
middle 50s...just a bit above normal...and light patchy fog may form
near the coast Wednesday morning in the predawn hours. High temperatures
Wednesday will again be slightly above normal from around 75 to
80...supporting a chamber of Commerce type weather day. Light
south southeast winds may bring a bit of moisture back into the
region by Wednesday night...supporting increased low
temperatures...which will be around 55 to 60...about 10 degrees
above normal. Winds will still be light enough to where light
patchy fog may develop again Thursday morning.
Long term /Thursday through through tuesdays/...
weak front on Friday gives way to weekend warmup then another
stronger front Sunday evening. Rain chances look somewhat limited.
Middle and upper level ridging will persist across central and western
Texas Thursday keeping middle and lower levels dry with modest easterly
onshore flow at the surface. Thursday looks warm with just a bit of
middle and upper level cloud cover. Highs will stretch close to 80
across the area.
The increasing plains convergence sends a cold front
southward...moving through during the day on Friday. A bit of low
level moisture will be in place to overrun the frontal slope and
bring a slight chance of rain and a better shot at fairly thick
cloud cover. Temperatures will drop about 5 to 7 degrees from
Thursday to Friday...with about half of that from increased cloud
cover and the other half from very modest surface cold advection.
A potent short wave trough/closed low works into the southwestern US
later in the day Friday and lowering pressure over the plains
results in surface winds locally shifting back to the southeast by
Saturday morning. This increased southeast flow is accompanied by a
deepening of low level moisture which may spark a shower or two
overnight Friday night into Saturday. Kept the rain chances a little
more measured on Saturday than guidance consensus with strong
southwesterly downsloping flow likely capping convection and drying
the middle and lower levels precipitation will likely be limited to showers and
areas of light stratiform rain that form in stronger warm
advection...with those stronger areas of warm air advection expected to be few and
far between. Additionally middle and upper level DCVA remains focused
to the north of the region.
Did go with a little higher probability of precipitation Saturday night into Sunday with a
little better 850-700mb convergence for showers as a trough axis in
this region passes through. Precipitation amounts look quite light though
as region lies directly under the jet maximum core by this point with no
real deep layer lifting except for modest 850-700mb convergence.
That convergence decreases through the day Sunday and tailed probability of precipitation
down as a result.
Differences in the deterministic GFS/European model (ecmwf) output develop at this
point primarily with the handling of the upper low/trough to the
west. The European model (ecmwf) is the more progressive of the two sweeping a system
through rather quickly while the GFS keeps a lagging low back to the
west through the middle of next week. GFS ensemble runs favor the
lagging GFS and the overall jet pattern supports a less progressive
solution...but probably not quite as slow as the GFS. The European model (ecmwf) is
slightly faster with a sweeping cold front on Sunday but sensible
weather timing is reasonably close for now and continued a fairly
robust frontal passage on Sunday evening with about a 15 degree
temperature drop from sundays highs to mondays highs. Both GFS/European model (ecmwf)
support at least some overrunning/persistent light rain low
cloudiness through Monday and Tuesday and kept low grade rain/shower
chances in the forecast during that time. /68-jgg/
now through Wednesday night...broad high pressure over the area will
shift slowly east...maintaining light to moderate winds and low seas
through the short term.
Thursday through Sunday... moderate east winds will shift to the
northeast Thursday evening with winds possibly briefly reaching
exercise caution levels part of the day on Friday. Wind speeds will
decrease briefly on Friday before increasing again out of the
southeast during the day Saturday and Saturday night. A slackening
of wind speeds is expected Sunday before a strong cold front sweeps
across the coast Sunday evening. Small Craft Advisory conditions
appear likely behind this front.
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