Area forecast discussion
National Weather Service San Angelo Texas
426 am CDT Tuesday may 21 2013
Today and tonight...
the main concern in the short term is with severe weather
potential across our eastern counties this afternoon and evening.
A fairly strong shortwave trough /currently over the southern
rockies/ will move east into the Southern Plains and North Texas
today. A surface cold front will push south across our northwestern
counties this morning...and through our central and southern
counties this afternoon. This front should exit our southeastern
counties by 7-8 PM this evening.
As lift from the approaching shortwave trough impinges on the
area...some of the models indicate convective development across
parts of the Big Country later this morning along and behind the
cold front. Have added 20-30 probability of precipitation across our northeastern counties
this morning for this possibility. With increasing vertical shear
and steep middle-level lapse rates...cannot rule out the possibility of
a few strong elevated storms with hail this morning. The main
severe weather potential...however...is this afternoon and evening
across our eastern counties...when favorable combination of vertical
shear and instability will be supportive of organized severe storms.
Storms are expected to develop along the southward-moving cold
front. Could have discrete supercells initially...before storms
organize into a quasi-linear mesoscale convective system. Our Heartland and Northwest Hill
country counties look to be on the southwest end of the anticipated
quasi-linear mesoscale convective system. Carrying the highest probability of precipitation across our Heartland
and Northwest Hill country counties.
The dryline has retreated west of our forecast area. The 00z NAM
and GFS boundary layer fields suggest that the dryline could make
an intrusion into the western Concho Valley and northern Edwards
Plateau this afternoon before being overtaken by the cold front.
With less cloud cover expected across these areas along with a
thermal ridging pattern at 850 mb...temperatures could well reach
the 90-95 degree range for highs before the cold front arrives.
Temperatures are expected to be appreciably cooler across the Big
Country...where the cold front arrives earlier in the day and
where greater cloud cover should develop.
Thunderstorm activity will end later this evening across our
far southeastern counties as the cold front continues to move
south. In the wake of the frontal passage...north winds will
diminish and become light overnight...as weak surface high
pressure settles south into our area. With this setup temperatures
will be cooler tonight...and going with overnight lows in the 60-65
degree range. While the GFS MOS looks too aggressive /at this time/
with the radiational cooling for tonight...our forecast lows may
need to be tweaked down further.
Wednesday through Friday...
both the GFS and the European model (ecmwf) show a shortwave ridge developing in
the upper levels across west central Texas. But they also show
showers and storms along the western edge across much of West
Texas...with the storms trying to move east into portions of west
central Texas each evening. Will keep the slight chance probability of precipitation in
the forecast as is for now.
Saturday through Tuesday...
upper level ridge intensifies and broadens...leaving west central
Texas in a hot and dry pattern. 850 mb winds remain out of the
south and southeast...which helps mitigates the temperatures a few
degrees...but still looking like readings well into the 90s for
Memorial Day.
&&
Preliminary point temps/pops...
Abilene 87 63 92 69 92 / 20 10 10 10 10
San Angelo 93 64 94 70 94 / 20 10 5 10 10
Junction 94 64 93 70 93 / 30 20 5 5 10
&&
Sjt watches/warnings/advisories...
none.
&&
$$
19/07/07
