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May 22, 2008 1300 UTC Day 1 Convective Outlook
Updated: Thu May 22 12:30:17 UTC 2008  (Print Version)
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the central plains this afternoon and tonight....   Please read the latest public statement about this event.

  | | |  
SPC Day1 1300Z Outlook Categorical SPC Day1 1300Z Outlook Categorical Legend
 Forecast Discussion
   SPC AC 221225
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0725 AM CDT THU MAY 22 2008
   
   VALID 221300Z - 231200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS SWRN NEB...WRN
   KS...EXTREME NWRN OK...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM WRN NEB AND
   EXTREME SERN WY TO PORTIONS NW TX/SW OK...
   
   ...CENTRAL/SRN HIGH PLAINS...
   DEEP UPPER LOW WILL REMAIN NEARLY STATIONARY DURING THE PERIOD...OR
   EVEN RETROGRADE SOME...AS STRONG UPPER JET DIGS ALONG THE WEST
   COAST.  AHEAD OF THIS SYSTEM...SURFACE LOW WILL LIKELY REMAIN IN
   PLACE OVER ERN CO WITH DRY LINE BECOMING BETTER DEFINED SWD FROM
   THIS LOW ACROSS FAR WRN KS INTO THE ERN TX PANHANDLE THIS AFTERNOON.
   WARM FRONT IS BECOMING ESTABLISHED THIS MORNING ACROSS THE CENTRAL
   PLAINS FROM NERN CO INTO CENTRAL MO...WITH WEAKENING SURFACE FRONT
   FROM NERN OK INTO THE CENTRAL GULF COAST STATES.  S-SW OF THIS
   DIMINISHING FRONT...VERY RICH GULF MOISTURE HAS SURGED NWD EARLY
   THIS MORNING WITH NEAR 70F DEW POINTS NOW INTO SRN OK AND MID 60S
   INTO FAR S-CENTRAL/SWRN KS. STRONG 70-80 KT SLY MID LEVEL JET WILL
   OVERSPREAD THE CENTRAL HIGH PLAINS ATOP NWRN EDGE OF THIS MOISTURE
   RETURN WITH 50-60 KT SWLY H5 WINDS DEVELOPING ACROSS DRY LINE OVER
   THE SRN HIGH PLAINS.  GIVEN VERY STEEP LAPSE RATES AND RICH LOW
   LEVEL MOISTURE...SETUP WILL THEREFORE BECOME QUITE VOLATILE OVER
   MUCH OF THE REGION WITH POTENTIAL FOR VERY LARGE HAIL AND A FEW
   SIGNIFICANT TORNADOES INTO THE MID EVENING.
   
   DEVELOPMENT IS EXPECTED TO PERSIST WITHIN STRONG ELY UPSLOPE FLOW
   INTO NERN CO/NWRN NEB/SERN WY NORTH OF THE SURFACE LOW...WITH THREAT
   OF ISOLATED LARGE HAIL AS MODEST SURFACE HEATING SUPPORTS MARGINAL
   INSTABILITY.  OTHERWISE...EXPECT SFC-BASED TSTMS TO DEVELOP INVOF
   ELONGATED SFC LOW AND NEARBY DRYLINE AND WARM FRONTAL SEGMENTS FROM
   SRN NEB INTO WRN KS WHICH SHOULD MOVE ACROSS WARM FRONTAL ZONE. 
   RELATIVELY BACKED FLOW INVOF WARM FRONT WILL ENHANCE EFFECTIVE BULK
   SHEAR...LOW LEVEL SRH AND BOUNDARY LAYER VORTICITY.  THUS ANY MATURE
   STORMS INTERACTING WITH THE FRONTAL ZONE MAY PRODUCE TORNADOES BUT
   THEN MOVE QUICKLY INTO UNFAVORABLE SFC AIR MASS.
   
   VERTICAL SHEAR INCREASINGLY WILL FAVOR SUPERCELLS/TORNADOES FARTHER
   S IN WRN PORTION OF MOIST SECTOR WITH TIME...AS CAPPING WEAKENS
   ALONG DRYLINE.  THIS ESPECIALLY IS A CONCERN LATE AFTERNOON INTO
   EARLY EVENING WHEN LIFTED PARCELS STILL ARE SFC-BASED AND
   STRENGTHENING LLJ GREATLY ENLARGES HODOGRAPHS IN ENVIRONMENT OF ANY
   EXISTING SUPERCELLS.  POTENTIAL WILL BUILD SWD ALONG KS SEGMENT OF
   DRYLINE THROUGH AFTERNOON.  STRONG MERIDIONAL COMPONENT OF MEAN FLOW
   AND POTENTIAL FOR SCATTERED-NUMEROUS TSTM COVERAGE PROVIDES SOME
   STORM-SCALE UNCERTAINTIES PRECLUDING GREATER SIGNIFICANT
   HAIL/TORNADO PROBABILITIES ATTM.  HOWEVER...THERE SHOULD BE
   SUFFICIENT SBCAPE-- E.G. 2000-2500 J/KG OVER MUCH OF WRN KS AND
   PERHAPS A SMALL PART OF SWRN NEB -- TO SUPPORT POTENTIAL FOR SEVERAL
   DISCRETE/CYCLIC/TORNADIC SUPERCELLS DURING AFTERNOON AND EARLY
   EVENING HOURS.  SUPERCELLS/TORNADO POTENTIAL MAY PERSIST WELL INTO
   NIGHTTIME HOURS...ESPECIALLY WITH SWD EXTENT...ALTHOUGH EVOLUTION
   INTO MORE LINEAR SEGMENTS IS EXPECTED AFTER DARK. 
   INCREASING/ELEVATED TSTM COVERAGE WELL N OF WARM FRONT -- ACROSS
   N-CENTRAL PLAINS...WILL RESULT IN POTENTIAL FOR SVR HAIL AS FAR N AS
   PORTIONS SD.
   
   ...SRN HIGH PLAINS...
   STRONGER BUOYANCY -- E.G. 3000-4000 J/KG MLCAPE -- AND GREATER
   MLCINH EACH ARE FCST SWD OVER ERN PANHANDLES AND WRN OK...COMPARED
   TO FARTHER N.  STRONG CAPPING AND MID LEVEL HEIGHT RISES ARE
   EXPECTED TO LIMIT POTENTIAL COVERAGE...AND THREAT THEREFORE BECOMES
   MORE ISOLATED AND CONDITIONAL WITH SWD EXTENT ACROSS SRN HIGH
   PLAINS.  HOWEVER...ENVIRONMENT SHOULD BE MORE CONDUCIVE TO
   LONGER-LIVED SUPERCELLS SHOULD CAP BREAK GIVEN GREATER STEERING FLOW
   ACROSS THE DRY LINE. ANY SUPERCELL WHICH DEVELOPS COULD PRODUCE A
   STRONG TORNADO ALONG WITH VERY LARGE HAIL INTO THE EARLY TO MID
   EVENING.
   
   ...ERN TX INTO ARKLATEX AND ERN OK...
   SCATTERED TSTMS ARE EXPECTED TO DEVELOP THIS AFTERNOON IN ZONE OF
   WEAK LARGE SCALE ASCENT/DESTABILIZATION ALOFT...JUXTAPOSED WITH STG
   DIURNAL HEATING...RICH BOUNDARY LAYER MOISTURE...AND RELATIVELY WEAK
   SBCINH.  MAIN LIMITING FACTOR WILL BE LACK OF SUBSTANTIAL LOW LEVEL
   FOCI...ESPECIALLY PRIOR TO DEVELOPMENT OF ANY OUTFLOW BOUNDARIES. 
   HOWEVER...12Z LCH/FTW SOUNDINGS INDICATE VERY STEEP MID LEVEL LAPSE
   RATES AND FCST SOUNDINGS DEPICT ENLARGED LOW LEVEL HODOGRAPHS...
   ESPECIALLY IN NARROW ZONE OF SELY SFC WINDS IMMEDIATELY AHEAD OF
   UPPER LOW AND S OF WARM FRONTAL ZONE.  ALTHOUGH MID-UPPER LEVEL FLOW
   SHOULD BE RELATIVELY WEAK...BRIEF SUPERCELL ORGANIZATION IS POSSIBLE
   AMONG MORE PREDOMINANT MULTICELLULAR MODES.  THEREFORE WILL INCLUDE
   MRGL PROBABILITIES FOR HAIL AND DAMAGING CONVECTIVE GUSTS.
   
   ..EVANS/EDWARDS/SMITH.. 05/22/2008
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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