SPC AC 151958

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0158 PM CST Sun Jan 15 2017

   Valid 152000Z - 161200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   WEST-CENTRAL/NORTH-CENTRAL TX TO FAR SOUTHERN OK...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
   SOUTHERN PLAINS...

   ...SUMMARY...
   Scattered severe thunderstorms will be possible this afternoon and
   tonight across west-central to north-central Texas and southern
   Oklahoma. A few tornadoes, damaging winds, and large hail are
   anticipated.

   ...20Z Update...
   The severe threat across southwest into west TX is expected to
   continue increasing through the afternoon. The only change to the
   prior outlook across this area has been to account for the eastward
   movement of the cold front and line of pre-frontal convection. The
   northern extent of the appreciable severe risk remains confined by a
   shallow cold and stable airmass over the TX Panhandle into southwest
   OK. For more near-term meteorological details (through ~2130Z) on
   the developing severe risk across southwest TX, see Mesoscale
   Discussion 52.

   There is some concern that isolated showers and thunderstorms
   ongoing over parts of east TX in a warm air advection regime may
   become surface based this afternoon and evening. Low to mid 60s
   surface dewpoints across this region will continue to shift
   northward into the Metroplex over the next few hours as a warm front
   lifts northward. RAP/HRRR forecast soundings suggest that an
   isolated tornado threat may develop with pre-frontal warm sector
   convection as a low-level jet strengthens across central/north TX in
   the 00-03Z timeframe. Have accordingly made a minor adjustment to
   the 5% tornado probabilities in/around the Metroplex to account for
   this scenario.

   ..Gleason.. 01/15/2017

   .PREV DISCUSSION... /ISSUED 1030 AM CST Sun Jan 15 2017/

   ...Portions of Texas into southern Oklahoma...
   Mid/late morning water vapor satellite imagery shows an
   east/northeastward-moving upper low nearing the El Paso/far west TX
   vicinity. This low will continue northeastward and increasingly take
   on a negative tilt over the southern High Plains. Ahead of this
   system, 30-45 kt southerly low-level winds (1-3 km above ground
   level) will continue to transport a seasonally moist air mass
   northward, with lower 60s F surface dewpoints expected to reach
   parts of north-central/northeast TX late today, while some middle
   60s F surface dewpoints will reach parts of south-central TX/Hill
   Country. Persistent low clouds and continued convection to the north
   of a warm front cast some uncertainty on the exact degree of
   destabilization later today, particularly with northward extent into
   north-central TX and far southern OK.

   Current thinking is that increasingly strong thunderstorms should
   develop by around mid-afternoon initially across southwest TX in
   vicinity of the Permian Basin and western Edwards Plateau. The most
   numerous storms through early evening should occur near the
   eastward-advancing front across west-central TX. However, sufficient
   low-level moisture and modest capping may allow for some
   front-preceding surface-based storms to develop late this
   afternoon/early evening across the Edwards Plateau/Hill Country
   vicinities toward the I-35 corridor of north-central Texas. Given
   that deep-layer/low-level shear will be increasing through early
   evening, both initial semi-discrete/line-embedded supercells will be
   possible ahead of an increasingly prominent linear mode near the
   cold front this evening. Bouts of large hail will be possible
   especially with initial development across west TX this afternoon,
   but damaging winds and isolated tornadoes should become the primary
   risks into this evening across a large part of
   west-central/north-central TX.

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