Scientific Forecaster Discussion
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Area forecast discussion...updated
National Weather Service Brownsville Texas
700 PM CDT Wednesday Apr 23 2014
Discussion...updated for latest aviation discussion below.
Aviation...high level clouds continue to stream northward across the
area from thunderstorm activity across northeastern Mexico. VFR
conditions this evening will drop to MVFR levels later this evening
and overnight as ceilings drop to around 1500 feet. Ceilings at
mfe could drop to around 1000 feet between 09-13z. Persist
moderate southeast winds will bring moisture in under the stable
layer later tonight but winds should be to strong for any significant
fog to develop at taf sites overnight. VFR conditions expected to
develop across all terminals by 18z Thursday.
Previous discussion... /issued 145 PM CDT Wednesday Apr 23 2014/
Short term /tonight through Thursday night/...the main first
period issue will be increased south southeast winds due to a
deepening storm system in the plains tightening up the local
pressure gradient in association with resident high pressure over
the northwest Gulf. This will actually have more impact for the
marine areas...see below discussion...but moderate to breezy winds
tonight and early tomorrow will represent a return to a more
typical wind regime for deep south Texas and the rgv. Moisture
will keep piling up along the coastal regions tonight...with
copious low cloudiness setting up under a stable thermodynamic
profile that will deepen through the boundary layer. Look for 10
to 20 miles per hour winds through tonight...diminishing somewhat after
midnight. Low temperatures will be near 70 degrees.
Moderate south southeast winds will continue east of U.S. 281
Thursday...but high pressure and dry air will move in from the north
and west...with a dry line moving into the Rio Grande plains from
the west...and a trailing cold front moving into south central Texas
from the north. Cloud cover may be a category less out west tomorrow
as a result...or partly cloudy as opposed to mostly cloudy. Winds
will decrease to light Thursday afternoon for the western counties
of Zapata...Jim Hogg and Starr...possibly shifting to southwest.
Could see some pop up showers north of the County Warning Area along the front/dry
line boundary...but not expecting much locally in the drier regime
out west. High temperatures will range from the 80s near the coast to the
middle to upper 90s far west.
Thursday night temperatures will again be near 70...with low level clouds
near the coast but clearer inland. Light winds may allow for patchy
to areas of light to MDT fog as overnight low temperatures and high dew
points bump up against each other.
Long term /Friday through Wednesday/...hot and dry conditions
this weekend into early next week...
Mainly zonal middle level flow Friday will give way to southwesterly
flow Saturday into Sunday as a middle level trough moves across The
Rockies into the Central Plains. Cyclogensis will occur in the High
Plains and with high pressure located in the Gulf winds will become
breezy this weekend. Saturday night into Sunday a 80 knot upper
level jet and weak vorticity maximum could lead to an isolated
thunderstorm out west but as of right now dont think its Worth
mentioning in the public zones.
For Sunday afternoon and Monday...GFS and European model (ecmwf) coming into better
agreement concerning the movement of a dryline/trough with very dry
air behind it. Fairly low humidity /9-20% west of Highway 281/ is
expected which will also cause high temperatures both days to soar
into the upper 90s and lower 100s. Used a little more ecx during
this time period /ecx warmer than mex/ to bring highs into the lower
100s across more areas west of Highway 281 and middle to upper 90s
between Highway 281 and Highway 77.
The next front arrives Tuesday with cooler temperatures and dry
weather continuing. Looks to be a dry front as well so no
precipitation. Breezy conditions expected behind the frontal passage
on Tuesday afternoon. Afternoon highs will be in the upper 80s to
lower 90s Tuesday.
Marine...now through Thursday night...a storm system deepening over and
moving east out of the plains is tightening the pressure gradient
and boosting southeast winds today. Moderate southeast winds will
approach 20 kts over the Gulf tonight...and low seas will build to
moderate...with low end Small Craft Advisory conditions possible.
Winds should diminish Thursday as the storm system shifts east and
high pressure fills into West Texas from farther west. Light to
moderate onshore winds and moderate seas will prevail Thursday and
Friday through Monday...small craft exercise caution Friday night
will give way to small craft advisories Saturday through Sunday
night as strong low pressure develops across western Texas and
southeasterly winds increase. Seas will also increase to 5-7 feet
by Saturday night through Sunday night. Exercise caution will also
be possible Monday as seas are slow to fall despite surface winds
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