Jan 21, 2010 2000 UTC Day 1 Convective Outlook
Updated: Thu Jan 21 23:18:21 UTC 2010
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Categorical Graphic
20100121 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20100121 2000 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20100121 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20100121 2000 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 212315
   
   DAY 1 CONVECTIVE OUTLOOK AMEND 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0515 PM CST THU JAN 21 2010
   
   VALID 212315Z - 221200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NRN FL...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE MID
   SOUTH REGION...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER COASTAL PORTIONS OF
   CENTRAL/SRN CA...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF CNTRL/SRN AZ AND
   EXTREME SERN CA...
   
   AMENDED FOR ADDING SLGT RISK TO PARTS OF AZ/SERN CA
   
   .UPDATE...
   
   ...SERN CA...CNTRL/SRN AZ...
   HAVE UPGRADED PARTS OF CNTRL/SRN AZ AND EXTREME SERN CA TO
   CATEGORICAL SLGT RISK FOR THE POTENTIAL FOR DMGG WIND GUSTS/HAIL AND
   BRIEF TORNADOES.
   
   SATL WAVE IMAGERY SHOWS NEXT SPOKE OF VORTICITY ROTATING ONSHORE SRN
   CA WITH A CORRESPONDING INCREASE IN FRONTAL CIRCULATION TAKING PLACE
   ACROSS SERN CA.  THE RESULT HAS BEEN FOR A NARROWING AND
   INTENSIFICATION OF A BAND OF TSTMS THAT HI-RESOLUTION MODELS SUGGEST
   WILL MOVE/DEVELOP ACROSS CNTRL/SRN AZ DESERTS THROUGH THE EVENING. 
   SHEAR PROFILES ARE IMPRESSIVE WITH 0-1KM SRH AT KIWA SHOWING NEARLY
   450 M2/S2.  AT THE SAME TIME...A TAP OF LOW-LEVEL MOISTURE FROM THE
   GULF OF CA HAS RESULTED IN MID-UPR 50S DEW POINTS TO FAN OUT INTO
   THE DESERTS AND WILL BOOST INSTABILITY AS THE UPR LEVELS COOL WITH
   THE APPROACH OF THE UPR LOW.  EXPECT STORM MODE TO MAINLY BE IN THE
   FORM OF FORCED LINE SEGMENTS GIVING DMGG WIND GUSTS/HAIL. 
   HOWEVER...BRIEF TORNADOES WILL BE POSSIBLE WITH ANY EMBEDDED BRIEF
   SUPERCELLS/BOW-HEAD STRUCTURES. /JPR
   
   .PREV DISCUSSION... /ISSUED 157 PM CST THU JAN 21 2010/
   
   ...NRN AND CENTRAL FL...
   LARGE/STRONG SUPERCELL -- WHICH PRODUCED ONE OR MORE APPARENT
   TORNADOES IN THE PAST 1-2 HOURS -- IS NOW MOVING OFF OF COASTAL ST.
   JOHNS CO FL.  A TRAILING LINE OF STORMS EXTENDS WWD ACROSS THE NRN
   FL PENINSULA...AND WHILE SURFACE FLOW HAS VEERED IN THE WAKE OF THE
   PRIOR STORM...SOME SEVERE THREAT REMAINS NEAR AND S OF THE ONGOING
   W-E LINE.  WHILE THE MAIN THREAT APPEARS TO BE HEAVY RAINFALL...WILL
   MAINTAIN A SLIGHT RISK ACROSS THIS REGION.
   
   ...MID SOUTH...
   CONVECTION HAS BEEN SLOW TO ORGANIZE ACROSS THE MID SOUTH REGION
   THIS AFTERNOON...WHERE MODEST INSTABILITY HAS DEVELOPED INVOF THE
   UPPER LOW NOW CROSSING WRN TN/WRN KY.  WHILE LOW-LEVEL FLOW HAS
   VEERED TO SWLY ACROSS MUCH OF THE AREA...AMPLE SHEAR PERSISTS TO
   SUPPORT SOME SEVERE POTENTIAL.  WHILE PRIMARY THREAT APPEARS TO BE
   TRENDING TOWARD HAIL/WIND...AN ISOLATED TORNADO OR TWO REMAIN
   POSSIBLE BEFORE STORMS DIMINISH THIS EVENING.
   
   ...COASTAL PORTIONS OF THE SRN HALF OF CA...
   WEAK INSTABILITY IS INDICATED BY MODEL/OBJECTIVE ANALYSIS OUTPUT
   ACROSS THE SRN HALF OF CA ATTM...AND FURTHER IMPLIED BY A LACK OF
   LIGHTNING WITH THE ONGOING SHALLOW CONVECTION.
   
   HOWEVER...STRONG FLOW ALOFT WILL LIKELY SUPPORT STRONG
   CONVECTIVELY-ENHANCED WIND GUSTS AT THE SURFACE...WITH ANY
   LOOSELY-ORGANIZED LINE OF LOW-TOPPED CONVECTION.  THUS...WILL
   MAINTAIN SLIGHT RISK ACROSS THIS REGION.
   
   ...PARTS OF SRN AZ...
   WILL MAINTAIN LOW SEVERE PROBABILITY ACROSS THIS REGION...AS A
   NARROW/FORCED LINE OF CONVECTION REMAINS A POSSIBILITY OVERNIGHT
   AHEAD OF A SMALL-SCALE UPPER FEATURE MOVING OUT OF THE ERN
   PAC/ACROSS SRN CA.  STRONG FLOW ALOFT SUGGESTS THE POTENTIAL FOR AN
   ISOLATED DAMAGING WIND EVENT OR TWO...BUT GIVEN THE FORECAST FOR
   MEAGER INSTABILITY...WILL NOT UPGRADE TO SLIGHT RISK THIS FORECAST.
   
   ..SELECT A FORECASTER.. 01/21/2010
   
   .PREV DISCUSSION... /ISSUED 1017 AM CST THU JAN 21 2010/
   
   ...NRN FL/SRN GA/FAR SRN SC...
   MCS CONSISTING OF EMBEDDED SUPERCELLS AND SMALL LINES WILL LIKELY
   CONTINUE EWD ACROSS NRN FL TODAY...BEING FED BY MODEST INSTABILITY
   OFF THE NERN GOM AND WITH SLY LOW LEVEL FLOW ACROSS CENTRAL FL. 
   APPEARS E-W ORIENTED WARM FRONT WILL BECOME ESTABLISHED THIS
   AFTERNOON...POSSIBLY AS FAR NORTH AS THE NERN FL/SERN GA BORDER...
   ALLOWING MID 60F SURFACE DEW POINTS TO PUSH NWD BEHIND THIS
   BOUNDARY.  LOW LEVEL SHEAR WILL LIKELY BE ENHANCED ALONG THE
   FRONT...WITHIN VERY STRONG MID/UPPER LEVEL WLY FLOW...SUPPORTING
   BOTH A RISK OF DAMAGING WINDS AND ISOLATED TORNADOES WITH POTENTIAL
   FOR A BOW ECHO TO EVOLVE AND PROGRESS RAPIDLY EWD ALONG THE
   BOUNDARY.  NORTH OF THE FRONT...SEVERE THREAT WILL BE MORE
   PROBLEMATIC WITH EXTENSIVE RAIN REINFORCING COOLER...MORE STABLE
   BOUNDARY LAYER AIR.  HOWEVER...IF PRESSURE FALLS AND INCREASING
   SSWLY LOW LEVEL FLOW ALLOW SURFACE WARM FRONT TO LIFT INTO SERN
   GA/FAR SRN SC THEN ATTENDANT SEVERE THREAT WILL ALSO SHIFT INTO THIS
   REGION LATER TODAY.
   
   ...MID SOUTH ACROSS THE TN VALLEY INTO SRN/CENTRAL APPALACHIANS...
   POTENT LOW AND MID LEVEL LOW PRESSURE OVER CENTRAL/NERN AR THIS
   MORNING WILL PROGRESS EWD ACROSS THE TN VALLEY THROUGH THE DAY. 
   ATTENDANT 70-90 KT WLY MID LEVEL JET WILL LIKEWISE SHIFT ACROSS NRN
   MS/AL WITH ENHANCED ASCENT AND PRONOUNCED SHEAR OVERSPREADING THIS
   REGION.  LOW LEVEL DESTABILIZATION WILL LIKELY REMAIN TEMPERED BY
   LOWER TO MID 50S F SURFACE DEW POINTS IN PLACE...ESPECIALLY GIVEN
   CONVECTIVELY MODIFIED BOUNDARY LAYER ACROSS MUCH OF AL/GA IN WAKE OF
   OVERNIGHT STORMS.  HOWEVER...AXIS OF NEAR 60F DEW POINTS SHOULD
   BEGIN TO NOSE ACROSS NRN MS AND INTO THE LOWER TN RIVER VALLEY
   REGION AS SURFACE WINDS VEER TO A MORE SWLY DIRECTION OVER THE LOWER
   MS RIVER VALLEY.  COMBINED WITH STEEPENING LOW LEVEL LAPSE RATES
   FROM DIURNAL HEATING...EXPECT AXIS OF MODEST INSTABILITY AND
   STEEPENING LOW LEVEL LAPSE RATES WILL DEVELOP AHEAD OF THE LOW
   CENTER.  SURFACE-BASED STORMS IN THE FORM OF LOW-TOPPED
   SUPERCELLS/SMALL BOW ECHOES SHOULD EVOLVE DURING THE EARLY AFTERNOON
   ACROSS THE MID SOUTH AND SPREAD GENERALLY EWD THROUGH THE DAY.  SRN
   EXTENT OF THE GREATER RISK AREA SHOULD BE MODULATED BY DEEPER
   SUBSIDENCE AND VEERING LOW LEVEL WINDS ACROSS CENTRAL MS/AL...WITH
   NRN EXTENT POSSIBLY SHIFTING INTO FAR SRN KY AS DESTABILIZATION
   OCCURS OVER TN.  THREAT SHOULD GRADUALLY DIMINISH WITH LOSS OF SFC
   HEATING TOWARDS THE SRN/CENTRAL APPALACHIANS THIS EVENING.
   
   ...SRN CA...
   ANOTHER ACTIVE DAY OVER THE REGION WITH NEXT STRONG IMPULSE AND
   ASSOCIATED LOW-TOPPED CONVECTION SPREADING ACROSS THE SRN CA COAST
   THROUGH THE DAY.  FORECAST SOUNDINGS MAINTAIN WEAK SURFACE-BASED
   INSTABILITY AND POTENTIAL FOR LOW-TOPPED SMALL
   LINES/SUPERCELLS...ESPECIALLY WITH MODEST DIURNAL WARMING ALONG THE
   COAST.  ALONG WITH HAIL AND ISOLATED DAMAGING WINDS AND POSSIBLY
   WATERSPOUTS/BRIEF TORNADOES SHOULD ACCOMPANY THE STRONGER STORMS.
   
   ...SRN/CENTRAL AZ...
   WITH APPROACHING STRONG MID/UPPER LEVEL SYSTEM NOW OFF THE SRN CA
   COAST PROGRESSING EWD ACROSS THE LOWER CO RIVER VALLEY
   OVERNIGHT...ENHANCED DEEP ASCENT WILL COLLOCATE ALONG A SURFACE COOL
   FRONT SHIFTING QUICKLY EWD ACROSS AZ.  WIND FIELDS REMAIN QUITE
   STRONG WITH ENHANCED LOW AND DEEP LAYER SHEAR.  ATTM...FORECAST
   SOUNDINGS SUGGEST INSTABILITY WILL BE QUITE WEAK WITH NEAR
   MOIST-ADIABATIC LAPSE RATES AHEAD OF THE FRONT.  HOWEVER...IT IS NOT
   OUT OF THE QUESTION FOR A NARROW LINE OF FORCED CONVECTION TO EVOLVE
   AND INCREASE THE RISK OF ISOLATED STRONG/DAMAGING WINDS LATE TONIGHT
   INTO PARTS OF CENTRAL/SRN AZ.  ATTM...WILL OPT TO MAINTAIN LOW
   SEVERE PROBABILITIES BUT AREA MAY NEED SLGT RISK IN LATER OUTLOOKS.
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z