Severe Weather - April 26th - Potential Tornado Outbreak
Before things get rolling, I want to bring attention to Sunday April 26th. Current indications are is that we will have a setup for a classic severe weather/tornado outbreak across the Southern Plains tomorrow, including the Metro area. SPC has alerted to this with very strong wording and has already outlooked the area of Central and Western Oklahoma in a moderate risk with a 45% hatch area. What this means is that there is a 45% probability of severe weather happening within 25 miles of a point, the hatched points out a 10% or greater probability of significant severe weather with in 25 miles of a point.
What can keep all this from going nuts? Storms that form on Saturday if they stick around or mix up the atmosphere too much, it'll take longer for things to get going. If there isn't enough of a lid on things early tomorrow, things could all just go up at once and then we'll have a heavy rain/hail/wind event.
Here is the current discussions covering this period. Graphics and such will be done in later posts.
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT SAT APR 25 2009
VALID 261200Z - 271200Z
...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN AND CNTRL PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER MIDWEST...
...SEVERE WEATHER OUTBREAK APPEARS LIKELY ACROSS PARTS OF THE SRN AND CNTRL PLAINS SUNDAY AFTERNOON AND SUNDAY NIGHT...
...SRN PLAINS AND CNTRL PLAINS...
A WELL-DEFINED 75 TO 85 KT MID-LEVEL JET IS FORECAST TO EJECT NEWD ACROSS THE SRN AND CNTRL PLAINS SUNDAY OUT OF THE BASE OF AN UPPER-LEVEL TROUGH OVER THE SRN AND CNTRL ROCKIES. THIS WILL CREATE A WIDESPREAD AREA WITH MODERATE TO STRONG VERTICAL SHEAR. AT LOW-LEVELS...ABUNDANT MOISTURE AND LOW-LEVEL SHEAR WILL BE IN PLACE ASSOCIATED WITH A BROAD 45 TO 60 KT LOW-LEVEL JET EXTENDING NNEWD ACROSS THE SRN AND CNTRL PLAINS. THE LOW AND MID-LEVEL JETS WILL BECOME JUXTAPOSED AS THE LARGE-SCALE ASCENT WITH THE MAIN UPPER-LEVEL TROUGH MOVES EWD INTO THE PLAINS. THIS WILL BE FAVORABLE FOR A WIDESPREAD SEVERE WEATHER EVENT SUNDAY AND SUNDAY NIGHT ACROSS PARTS OF WRN OK...CNTRL AND ERN KS...THE ERN TX PANHANDLE AND WCNTRL TX.
THE CURRENT THINKING IS THAT ONE OR TWO CLUSTERS OF ELEVATED STORMS WITH HAIL POTENTIAL SHOULD BE ONGOING SUNDAY MORNING ACROSS PARTS OF THE MODERATE RISK AREA. THIS CONVECTION SHOULD MOVE EWD AWAY FROM THE INSTABILITY AXIS DURING THE DAY ALLOWING FOR MODERATE TO STRONG DESTABILIZATION FROM CNTRL KS SWD ACROSS WRN OK...THE ERN TX PANHANDLE INTO THE LOW ROLLING PLAINS OF WCNTRL TX. MODEL FORECASTS ARE IN GENERAL AGREEMENT WEAKENING THE CAP BY EARLY TO MID-AFTERNOON INITIATING SCATTERED TO NUMEROUS THUNDERSTORMS ACROSS THE INSTABILITY AXIS. FORECAST SOUNDINGS FROM THE NAMKF AT 21Z ACROSS THE MODERATE RISK AREA SHOW DEEP UNSTABLE THERMODYNAMIC PROFILES WITH MLCAPE VALUES BETWEEN 2000 AND 2500 J/KG ACROSS MUCH OF THE MODERATE RISK AREA. IN ADDITION...0-6 KM SHEAR ACROSS THE WARM SECTOR AIDED BY THE MID-LEVEL JET SUNDAY AFTERNOON RANGE FROM 40 TO 55 KT WITH STRONG SPEED SHEAR IN THE BOUNDARY LAYER AND ADEQUATE DIRECTIONAL SHEAR FOR SUPERCELLS AND TORNADOES. CURVED HODOGRAPHS ALONG WITH LOW LCL HEIGHTS SUGGEST SOME STRONG TORNADOES WILL OCCUR LATE SUNDAY AFTERNOON INTO THE EVENING. IF THE CONVECTION ONGOING SUNDAY MORNING DOES INDEED MOVE EWD AWAY FROM THE AXIS OF INSTABILITY...ALLOWING FOR MODERATE TO STRONG DESTABILIZATION...THEN A TORNADO OUTBREAK MAY OCCUR ACROSS THE MODERATE RISK AREA.
FORECAST SOUNDINGS AT 21Z SUNDAY ALSO SUGGEST THE STORMS SHOULD BE EFFICIENT HAIL PRODUCERS. SUPERCELLS SHOULD BE CAPABLE OF PRODUCING VERY LARGE HAIL ESPECIALLY FROM SCNTRL KS SWD ACROSS THE ERN TX PANHANDLE...WRN OK INTO WCNTRL TX. LARGE HAIL COVERAGE SHOULD BE GREATEST FROM ECNTRL KS ACROSS WRN OK WITH MORE ISOLATED COVERAGE ACROSS WCNTRL TX WHERE CONVECTIVE COVERAGE IS NOT EXPECTED TO BE AS GREAT DURING THE EARLY EVENING. WIND DAMAGE SHOULD ALSO ACCOMPANY SUPERCELLS AND LINE-SEGMENTS DURING THE LATE AFTERNOON AND EVENING. A POTENTIAL FOR VERY STRONG WIND GUSTS SHOULD ALSO EXIST ESPECIALLY ACROSS THE NRN PART OF THE MODERATE RISK AREA AS LOW-LEVEL FLOW INCREASES AND LINE-SEGMENTS APPEAR MORE LIKELY.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
245 PM CDT SAT APR 25 2009
.DISCUSSION...
AS FAR AS SUNDAY GOES...SOMEWHAT DEPENDENT ON WHAT HAPPENS TO TONIGHT AND WHICH MODEL YOU PREFER. GFS LOOKS A LITTLE MOREVOLATILE WHILE THE NAM APPEARS TO HAVE WEAKER CAP WITH STRONG LARGE SCALE LIFT...WHICH WOULD LEAD TO A LOT OF STORMS AND POSSIBLY LARGE THUNDERSTORMS CLUSTERS...AS OPPOSED TO MORE DISCRETE STORMS. HOWEVER...LCLS WILL BE LOW AND LOWER/DEEP SHEAR IMPRESSIVE ON BOTH MODELS...SO SEVERE WEATHER THREAT APPEARS SIGNIFICANT.
WITH WESTERN TROUGH AND FRONTAL BOUNDARY MAKING PASSES AT REGION... DAY TO DAY CHANCES FOR STRONG-SEVERE WEATHER WILL CONTINUE THROUGH MUCH OF THE WEEK.
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Originally Posted by Thunder
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