Nov 20, 2014 1630 UTC Day 1 Convective Outlook
Updated: Thu Nov 20 16:26:44 UTC 2014 (20141120 1630Z Day 1 shapefile | 20141120 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20141120 1630 UTC Day 1 Outlook Graphic
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Tornado Graphic
20141120 1630 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.
Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20141120 1630 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.
Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20141120 1630 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.
Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 201626

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1026 AM CST THU NOV 20 2014

   VALID 201630Z - 211200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   OCCASIONAL LIGHTNING MAY OCCUR WITH LAKE-EFFECT CONVECTIVE PLUMES IN
   THE LEE OF LAKES ERIE AND ONTARIO THROUGH EARLY EVENING. ISOLATED
   THUNDER MAY OCCUR OVER THE CENTRAL AND NORTHERN CALIFORNIA COASTAL
   WATERS THIS AFTERNOON.

   ...SYNOPTIC SETUP...
   BROAD...TWO-STREAM CYCLONIC FLOW WILL PREVAIL OVER THE CONUS THROUGH
   EARLY FRI...DOWNSTREAM FROM PERSISTENT BLOCK N OF AK. MAIN COMPONENT
   OF ERN CANADIAN TROUGH WILL FURTHER AMPLIFY SE ACROSS THE GRT LKS
   AND NERN STATES AS ASSOCIATED SHORTWAVE TROUGH NOW CROSSING LK
   SUPERIOR SWEEPS E TO THE LWR LKS. IN THE SRN BRANCH...A SERIES OF
   WEAK DISTURBANCES WILL CROSS THE SWRN STATES AHEAD OF STRONGER E
   PACIFIC TROUGH NOW APPROACHING CNTRL CA.

   ...LEE OF LKS ERIE AND ONT THROUGH EARLY EVE...
   LAKE-EFFECT CONVECTIVE BANDS WILL PERSIST...WITH A GRADUAL SWD
   MOVEMENT EXPECTED THROUGH THIS EVE. SPORADIC CG LIGHTNING STRIKES
   MAY OCCUR GIVEN EXISTING THERMODYNAMIC PROFILES. AS UPSTREAM
   SHORTWAVE IMPULSE MOVES ACROSS REGION THIS EVE...EXPECT GRADUAL
   VEERING OF LOW-LVL FLOW...WITH BOUNDARY LAYER WINDS BECOMING LESS
   UNIDIRECTIONAL AND ORIENTED LESS PARALLEL TO THE LONG AXES OF THE
   LAKES. THIS WILL DISRUPT CONVECTIVE PLUME DEVELOPMENT...AND LESSEN
   LIKELIHOOD FOR ADDITIONAL THUNDER.

   ...CSTL NRN/CNTRL CA THROUGH LATE AFTN...
   COOLING AND ASCENT WILL ACCOMPANY E PACIFIC SHORTWAVE IMPULSE AS THE
   DISTURBANCE CONTINUES ESE TO THE CNTRL CA CST BY EVE. BOUNDARY LAYER
   BUOYANCY OVER CA...HOWEVER...WILL BE LIMITED BY WARM CONVEYOR BELT
   CLOUD BAND AND ASSOCIATED RAINFALL/EVAPORATIVE COOLING. THIS SETUP
   ALSO WILL DIMINISH LOW-LVL ONSHORE FLOW/INFLUX OF MARITIME AIR.
   WHILE CONVECTION ASSOCIATED WITH THE MAIN UPR VORT MAY REMAIN
   SUFFICIENTLY DEEP TO YIELD A FEW LIGHTNING STRIKES OVER THE CSTL
   WATERS...LIKELIHOOD FOR INLAND PENETRATION OF SUCH ACTIVITY APPEARS
   LIMITED. 
     
   ...E/NE TX LATE IN PERIOD...
   CONVECTION LIKELY WILL DEEPEN/STRENGTHEN OVER MUCH OF E TX TNGT AND
   EARLY FRI AS WAA/MOISTURE TRANSPORT INCREASE AHEAD OF WEAK
   DISTURBANCES PRECEDING CA TROUGH. ATTM...SATELLITE PW DATA AND SFC
   OBSERVATIONS SUGGEST THAT LIMITED QUALITY OF MOISTURE RETURN AND
   MODEST DEGREE OF ASCENT WILL PRECLUDE SUFFICIENT DEEPENING OF
   CONVECTION TO POSE AN APPRECIABLE RISK FOR LIGHTNING. THIS NOTION IS
   FURTHER SUPPORTED BY THE FACT THAT MID-LVL LAPSE RATES ALSO WILL
   REMAIN WEAK. AN ISOLD LIGHTNING STRIKE OR TWO MAY...HOWEVER...OCCUR.

   ..CORFIDI/COHEN.. 11/20/2014

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z