Feb 9, 2018 1300 UTC Day 1 Convective Outlook
Updated: Fri Feb 9 12:33:10 UTC 2018 (20180209 1300Z Day 1 shapefile | 20180209 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180209 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Tornado Graphic
20180209 1300 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
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20180209 1300 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
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20180209 1300 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
No Risk Areas Forecast
   SPC AC 091233

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0633 AM CST Fri Feb 09 2018

   Valid 091300Z - 101200Z


   Thunderstorms are expected to develop from parts of southeast Texas
   through the lower Mississippi Valley and the Southeast States,
   mainly later today through tonight.

   A longstanding, intense, mid/upper-tropospheric cyclone will persist
   over the Baffin Island region and adjoining parts of northeastern
   Canada.  Most progs keep the cyclone over this region for at least
   ten more days.  However, the configuration of cyclonic flow around
   the associated longwave trough will change, starting today, as a
   series of shortwaves traverse the back side of the cyclone over
   central/western Canada and across the western and northern U.S. 
   Height falls will occur across a broad swath of the Plains, Rockies
   and Intermountain West, as a strong shortwave trough digs southward
   and southeastward from coastal BC and the northern Rockies.  That
   perturbation should reach WY, southern ID and OR by 12Z.  By then, a
   larger-scale trough will become established from WY to NM, phasing
   with a broad, weak, pre-existing, southern-stream height weakness
   over northern MX.  As that occurs, a series of low-amplitude
   shortwave perturbations and vorticity maxima will pivot cyclonically
   across northern MX, with a few ejecting northeastward over
   south/east TX toward the lower Mississippi Valley.

   At the surface, a cold front from northern IL across KS is forecast
   to shift southward/southeastward through the period.  By 12Z this
   front should extend from a weak wave low near EVV southwestward
   across AR, north-central/west-central TX and east-central NM.  A
   separate baroclinic zone, demarcating well-modified Gulf marine
   layer from a more stable, continental/polar air mass, will remain
   quasistationary through much of the period over the northern and
   western Gulf before drifting northward over LA shelf/coastal waters

   ...Southeast TX to Southeast States...
   Isolated to widely scattered thunderstorms are possible episodically
   through the period across a long swath of the southeastern U.S.  A
   lack of both more robust theta-e and stronger deep-layer instability
   (including boundary-layer lapse rates) keeps severe potential too
   small and conditional to warrant categorical probabilities at this

   Gradual moistening and destabilization of the elevated return-flow
   plume is expected as a broad sheet of warm advection becomes
   established across the Gulf Coast region.  As this occurs, potential
   will increase for favorably moist parcels to reach an LFC.  This
   will occur initially in three belts that should overlap spatially in
   the outlook area, even if somewhat offset temporally:
   1.  Warm advection, moisture transport and at least weak low-level
   convergence atop a relatively stable boundary layer today, mainly
   over portions of GA and SC.  The early stages of this process appear
   to be underway from southeastern AL into southwestern GA, with
   expansion forecast as the ongoing precip/UVV plume shifts
   east-northeastward into deeper buoyancy.
   2.  A roughly east-west corridor of ascent today and tonight from
   the Mississippi Valley to the Carolinas, orthogonal to the southerly
   component of the sheet of southwesterly flow.
   3.  A southwest-northeast swath with greater moisture and CAPE from
   east TX and LA to the Arklatex, growing across the Mid-South and
   shifting eastward late tonight, within a generally 35-50 kt LLJ.

   Although midlevel lapse rates will remain modest, these processes
   over time should yield sufficiently tall buoyant layers to support
   mixed-phase lightning-production zones in deepening convective
   turrets.  Thunderstorm coverage should increase accordingly,
   especially tonight in combined regimes 2 and 3.  By the end of the
   period, a well-established low-level convergence zone should exist
   over the lower Mississippi Valley and south-central/southeastern LA,
   with thunderstorm coverage increasing to at least scattered.
   Forecast soundings suggest effective-inflow parcels may become close
   to surface-based the last few hours of the period around
   southeastern LA, but still with a shallow stable layer near the
   surface related to relatively cool shelf waters.  This regime should
   continue to destabilize gradually into early day-2 with marginal
   severe probabilities, as discussed in that outlook.

   ..Edwards.. 02/09/2018