Jan 17, 2017 2000 UTC Day 1 Convective Outlook
Updated: Tue Jan 17 19:57:21 UTC 2017 (20170117 2000Z Day 1 shapefile | 20170117 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170117 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 46,633 8,458,707 Houston, TX...San Antonio, TX...Corpus Christi, TX...Laredo, TX...Pasadena, TX...
Probabilistic Tornado Graphic
20170117 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
2 % 19,501 4,210,716 Houston, TX...Corpus Christi, TX...Laredo, TX...Pasadena, TX...Sugar Land, TX...
Probabilistic Damaging Wind Graphic
20170117 2000 UTC Day 1 Damaging Wind Probabilities Graphic
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.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 27,598 5,009,091 Houston, TX...Corpus Christi, TX...Laredo, TX...Pasadena, TX...Sugar Land, TX...
Probabilistic Large Hail Graphic
20170117 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 46,526 8,459,699 Houston, TX...San Antonio, TX...Corpus Christi, TX...Laredo, TX...Pasadena, TX...
   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...

   ...SUMMARY...
   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...

   ...TEXAS...
   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.

   ..Kerr.. 01/17/2017

   .PREV DISCUSSION... /ISSUED 1029 AM CST Tue Jan 17 2017/

   ...South Texas...
   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
   tonight. 

   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