Scientific Forecaster Discussion
fxus64 kcrp 210005 aaa
Area forecast discussion...updated
National Weather Service Corpus Christi Texas
705 PM CDT Wed Sep 20 2017
Discussion...see aviation section for 00z tafs.
Aviation...high clouds will continue to move across south Texas
this evening associated with diminishing convection southwest of
Laredo. High clouds should diminish during the overnight hours.
Could see patchy fog affect the inland coastal plains with MVFR
vsbys by 10z Thursday from Alice to Victoria. Isolated streamer
showers will be moving inland during the early morning hours that
could affect the crp area. Areas of MVFR ceilings will develop
over the coastal plains by 14-15z and continue into early
afternoon along with scattered showers. Scattered showers or
thunderstorms will be possible for the afternoon hours over the
coastal plains. Storms could provide MVFR vsby/ceilings.
Previous discussion... /issued 343 PM CDT Wed Sep 20 2017/
Short term (tonight through Thursday night)...
Main concern is the rain chances on Thursday and into Thursday
night. Water vapor imagery is showing a slow-moving through near
then Big Bend region, with convection developing along the Sierra
Madre south of The Big Bend. As this wave approaches the area along
with some weak jet dynamics and some weak diffluence, that should be
enough to trigger some showers and isolated thunder on Thursday.
Generally did not go higher than 40 pops as in the previous
forecast, and kept rain chances in for pretty much everyone (20 pops
or more). Given slow-moving system, timing could be a bit of an
issue but overall played more of a sea-breeze scenario as expect
some daytime heating to push some of the convection farther west in
the afternoon unless upper dynamics move too fast and curtail it
Before that, could have some coastal showers toward morning which
will move inland and develop farther inland as per previous
paragraph. Some of the convection may linger in the evening, with
some coastal showers possible again overnight. However, confidence
in the rainfall in the evening and overnight is not that high as
unsure on the timing of the trough (may be too far east to help and
could actually be on the unfavorable side by then). Also, the
placement of mid level dry air after 06z could curtail rainfall in
the Gulf waters (right now mainly NE areas). Still, with
uncertainties still there will prefer to go with minor changes to
the rainfall forecast for Thursday night.
Another warm day on Thursday (not as warm as today but warm) with
humid conditions. Heat indices in the afternoon will be at or above 105f
most southern locations at least for an hour. Overnight lows will be
above average given the warm, humid airmass. Overall, used a blend
of consensus and WRF-bias corrected temperature forecast for minimum
temperatures (been doing OK for the last few runs). For highs, went
with a blend of previous, the shortblend and a MOS blend.
Marine (tonight through Thursday night)...
Generally weak to near moderate flow through the period, with
scatteed showers/isolated thunder on Thursday and lower rain chances
in the evening. Not much else to say
Long term (friday through wednesday)...
The long term begins with weak troughing stretched across the
southeastern US down through Texas as high pressure begins to build
in behind the trough north of the Ohio River valley and across the
Great Lakes region. In addition, a longwave trough begins to dig
through the West Coast. Heading into the weekend, the high begins to
extend farther south as the trough begins to develop a low pressure
system at its tail end and shifts slightly eastward. This will aid
in pwats to decrease to near 1.6 inches for the weekend as drier air
builds into the region, yet leave sufficient moisture across the
area to allow for isolated showers and possible thunderstorms to
continue, mainly across the waters and coastal plains. As this
occurs, the trough out to the west will slowly move eastward so that
by as early as Monday should help kick off convection across
northeastern Mexico that may drift eastward. With the upper trough
nearing the region, chances for showers and thunderstorms begin to
increase across the west-northwestern areas as pwats increase to
near or slightly above 2.0 inches through mid-week next week.
As for temperatures, will see temperatures relatively cool down by a
few degrees from the added moisture and cloud coverage by next week,
yet remain generally in the 90s area-wide during the day time hours,
with lows in the 70s.
Preliminary point temps/pops...
Corpus Christi 78 94 77 92 75 / 10 30 20 20 20
Victoria 76 92 74 91 72 / 10 40 20 20 10
Laredo 79 100 79 98 76 / 10 20 10 10 10
Alice 77 96 76 95 74 / 10 30 20 20 10
Rockport 82 91 81 89 79 / 20 40 20 20 20
Cotulla 77 98 76 97 75 / 10 20 10 20 10
Kingsville 78 96 77 94 75 / 10 30 20 20 10
Navy corpus 83 91 81 89 80 / 20 30 20 20 20