Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Brownsville Texas
411 am CST Thursday Jan 29 2015
Short term /now through Friday/...one more day of tranquil
weather before the next front arrives. Ridging aloft will continue
to provide tranquil weather today...with continued high cirrus
spreading through the region. Southeasterly winds will continue to
bring more moisture into the region...which will slightly hold
down temperatures relative to the past few days...only reaching
the upper 70s.
A weak frontal boundary will slide through the region early Friday.
Aloft...the large 500 mb trough off the West Coast will begin to shift
eastward...pushing the local ridge eastward and weakening it. This will
turn winds aloft more to the SW. While a cooler airmass is not
present behind the surface front...the shift to northeasterly winds at the surface
will oppose the southwesterly winds aloft...bringing much thicker lower cloud
cover and light rain and drizzle. The precipitation will focus
generally inland along the river...but will be minimal at best. Have
held general 20 probability of precipitation for those areas...with lower chances closer to
the coast. Denser cloud cover will also hold temperatures down in
the upper 60s.
Long term /Friday night through Wednesday/...extended period
remains challenging to say the least as upper trough/low west of
the Baja California of Mexico moves ever so slowly eastward not passing to
the east of the County Warning Area until Wednesday. A strong cold front adds to
the mix late Sunday into Monday.
The extended remains virtually unchanged with the uptick in rain
chances and the cool down in temperatures. Models remain
consistent with the general trend but differ in timing of the cold
front and the start of the more substantial probability of precipitation.
Moisture values and moisture depth increases steadily as
southwest flow strengthens and subtropical jet moves over head. As
dry as it has been it should turn quite wet a blend of the GFS and
European model (ecmwf) keeps probability of precipitation in the 30-50 percent range Sunday-Tuesday with
lower chances Saturday and Wednesday. GFS increases the probability of precipitation on
Sunday as it brings a cold front trough earlier then the European model (ecmwf).
The European waits until Monday with coastal trough developing.
The cold front is still forecast to move through the County Warning Area Sunday
night. Timing differences continue with GFS about 6 to 9 hours
faster than the European model (ecmwf). GFS also remains stronger with the cold
air advection dropping temperatures upwards of 30 degrees in a
12-18 hour period. Using a model blend The Drop in temperatures is
more gradual but Monday still looks to be the coldest day of the
week. Temperatures to stay cool into Tuesday with a slow increase
at the end of the period.
Marine...now through Friday...light southeast flow and light seas continue
today with one more day of high pressure. Conditions will change
Friday morning as a weak cold front moves through. Winds will shift
to the NE...but remain below advisory levels.
Friday night through Monday...an increase in southeast flow Friday
night and Saturday in advance of a slow moving storm system over
northwest Mexico. And cold front moving into the Southern Plains. This
strong cold front moves trough the Lower Texas coastal waters
Sunday evening or Sunday night. Small craft advisories are likely
through Monday. A coastal trough or low pressure area then forms
over the Gulf maintaining adverse conditions through the middle of
Preliminary point temps/pops...
Bayview/Port Isabel 74 59 68 60 / 0 0 20 10
Brownsville 77 58 71 60 / 0 0 20 10
Harlingen 78 57 70 59 / 0 0 20 10
McAllen 79 58 69 59 / 0 10 20 10
Rio Grande City 79 57 70 59 / 0 10 20 20
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