Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 171957
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0157 PM CST Tue Jan 17 2017
Valid 172000Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS PARTS OF DEEP SOUTH TEXAS INTO MIDDLE
TEXAS COASTAL AREAS...
Thunderstorm activity remains possible across parts of deep south
Texas and middle Texas coastal areas late this afternoon and
evening, with some risk for severe weather.
...20Z Outlook Update...
Deeper convective development capable of producing lightning has
been mostly confined to areas well to the north/cool side of the
surface cold front, which has advanced into the lower Rio Grande
Valley and mid/upper Texas coastal areas. Some lightning is now
evident with convection forming along the sea breeze, in the
vicinity of the front near/west of Corpus Christi. It is possible
that this activity could still intensify late this afternoon in the
presence of weak boundary layer CAPE and strong vertical shear
(beneath 40+ kt southwesterly 500 mb). However, it is also possible
that capping associated with relatively warm lower/mid tropospheric
air will continue to suppress convective development across much of
southern Texas into Texas coastal areas late this afternoon through
tonight. Models appear suggestive that forcing for ascent
associated with an upper impulse pivoting across and northeast of
the Big Bend region will be glancing across this region, while
low-level warm advection driven convection remains focused to the
north, across parts of central through eastern Texas.
...Southern Appalachians/upper OH Valley/Mid Atlantic Coast...
Lower/mid tropospheric moistening in southerly return flow is
contributing to weak destabilization and scattered convective
development across much of the region. This will tend to spread
eastward with associated forcing for upward vertical motion late
this afternoon and evening, and generally off the Mid Atlantic Coast
by/shortly after 18/06z. Lightning has recently been evident with
convection across north central Pennsylvania, and convection
elsewhere may similarly briefly intensify and become capable of
producing lightning. However, the coverage of any such additional
activity seems likely to remain below the 10 percent threshold
necessary for a categorical thunder outlook.
.PREV DISCUSSION... /ISSUED 1029 AM CST Tue Jan 17 2017/
A northeast/southwest-oriented front has now essentially stalled
across west-central LA and southeast/south TX (roughly 70-90 miles
inland from the coast). A subtle frontal wave was noted in
mid-morning analysis across far south TX (Brush Country vicinity)
with a moist air mass (near 70 F surface dewpoints) located along
and south/southeast of the front.
Late morning water vapor satellite imagery features an amplifying
trough over northeast Mexico, with an embedded shortwave impulse
expected to reach far west TX by mid-afternoon and parts of
northwest TX late tonight. DPVA and isentropic ascent focused
near/north of the surface front should lead to an increase in
scattered thunderstorms late this afternoon and especially into
While low-level moisture will remain rich near the front, relatively
warm upper-level temperatures should limit total buoyancy. Even so,
a moist air mass, in conjunction with 35-45 kt effective shear and
modestly strong/curved low-level hodographs (100-200 m2/s2 0-1 km
SRH), may yield weak/transient supercells near the surface front,
where locally damaging winds and/or a brief tornado could occur.
Otherwise, isolated marginally severe hail should be the main hazard
this evening/overnight with a few of the stronger storms to the
north of the surface front.
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z