Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Brownsville Texas
254 PM CDT Monday Oct 20 2014
Short term /now through Tuesday night/...
bro radar beginning to light up with mainly shower activity
'shotgunned' across much of the area and especially north of the
valley at this time. Surface convergence along with a little diffluence in
the upper levels with an upper low over the southwest and another
low over the Bay of Campeche. Morning sounding was moist with a precipitable water
of 1.84 inches and decent moisture up to 500 mb. Hrrr has a good
handle on the situation which progresses most of the precipitation
from northeast to southwest through the day with the better probability of precipitation
north of the valley transitioning to Zapata/Starr counties after
Expecting a repeat of probability of precipitation for overnight tonight. Confined probability of precipitation to
our northern sections of Gulf waters towards dawn then move that
area inland in the morning hours. Better moisture will reside in the
the ranchlands Tuesday and have trimmed probability of precipitation out of the valley until
later Tuesday. Coverage may not be as great as today due to drier
air moving into the 850-700mb layer. Less clouds and better mixing
of ll dry air led ME to increase highs a few degrees in the valley
Tuesday which MOS guidance supports as well /3-5 degrees over going
forecast/. Kept highs as is north of the valley with clouds and
Long term /Wednesday through Monday/...
the long term portion of the forecast should bring a return to drier
conditions across the forecast area as we turn off the atmospheric
Eyes will remain focused on the area of low pressure in the Bay of
Campeche as we head into the long term portion of the forecast.
Sufficient low-level moisture should remain across our region
Wednesday morning...with a weakening easterly flow helping to keep
precipitable water values hovering close to the 2 inch mark. With a
weak inverted surface trough emanating toward the Lower Texas coast
from the low...I expect enough forcing to be in place to keep at
least an isolated smattering of showers around for the morning hours.
The influence of the Bay of Campeche low should lessen at
mid-week...as it starts sliding eastward across the southern Gulf.
Winds should become more northeasterly as surface ridging builds
across the Ohio and middle Mississippi valleys. This should allow
the boundary layer to dry from the northeast during the day
Wednesday. Forecast soundings indicate the deeper moisture will
gradually get shoved south and west across the forecast area as the
As such...the greatest odds of seeing convection over eastern areas
should be in the morning hours. Locales over our more western and
southwestern areas could see shower/thunderstorm probabilities
holding on into the afternoon. The odds of seeing storms in most
places should be low...given weakening amounts of synoptic scale
forcing and that the deepest moisture will likely be seen at the
time of day when there's a diurnal minimum in instability. Still
though...it cannot be discounted by afternoon.
In addition to the rain problem...we continue to monitor the
possibility of some coastal flooding at mid-week. Rough swells from
the east-northeast will likely combine with higher than normal
astronmical tides to yield the threat during the Wednesday-Thursday
time frame. Stay tuned.
Any precipitation should end by Wednesday night...thanks to the
combination of a strengthening ridge aloft and (really) drier air
moves south of the Rio Grande. Ridging is expected to amplify
across middle-America for the latter part of the week as an upper-level
trough moves onshore the Pacific coast.
Given the expected strength of the ridge by this weekend and ample
sunshine...forecast temperatures have been raised a few degrees with
this forecast package. There's still a bit of uncertainty in things
during the day 5 through 7 time period though...as soil moisture
from any recent rainfall may temper highs just a bit. In addition
the upper ridge will likely weaken by Sunday or Monday...as the
upper trough moves across the nation's midsection.
Thanks to wpc and weather forecast office Corpus Christi for collaboration today. /53/
Now through Tuesday night...
moderate easterly flow will prevail through the short term
increasing into Tuesday night and gradually building seas over the
far offshore waters. Winds and seas are expected to reach into the
scec category Tuesday night. Isolated showers will be possible
through much of this period as well. /55/
Wednesday through Saturday...
small craft advisories may be required heading into middle-week thanks
to a strong pressure gradient over the marine area. Slightly
diminishing wind speeds may allow any small craft advisories to be
dropped at some point during the day Wednesday...but small craft
will likely need to continue to exercise caution through Thursday
morning. Increased ridging over the region for the latter part of
the week should result in more moderate winds and seas for Friday
and Saturday. /53/
Preliminary point temps/pops...
Bayview/Port Isabel 74 86 74 84 / 10 20 20 20
Brownsville 72 87 73 85 / 10 20 20 20
Harlingen 70 87 71 85 / 10 20 20 20
McAllen 71 88 70 86 / 10 20 20 20
Rio Grande City 69 86 69 86 / 20 20 20 20
South Padre Island 76 84 77 84 / 10 20 20 20
This product is also available on the web at:
Short term forecaster... scholl
long term forecaster... Butts