[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 111228
SWODY1
SPC AC 111226

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0626 AM CST SAT MAR 11 2006

VALID 111300Z - 121200Z

...THERE IS A MDT RISK OF SVR TSTMS FROM FAR ERN OK/NERN TX ACROSS
MUCH OF AR...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ERN SRN PLAINS INTO
THE NRN MS RIVER VALLEY EWD INTO THE OH/TN RIVER VALLEYS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER SERN CA...

...ERN SRN PLAINS/MS RIVER VALLEY INTO THE OH RIVER VALLEY...
BROAD UPPER TROUGH OVER THE WRN HALF OF THE U.S. WILL REMAIN
DOMINANT FEATURE THROUGH THE PERIOD...AHEAD OF WHICH A LARGE SWATH
OF STRONG MID/UPPER LEVEL SWLY WINDS HAS OVERSPREAD THE CENTRAL
U.S.. SEVERAL SUBTLE SHORTWAVE TROUGHS WILL CONTINUE TO EJECT NEWD
AWAY FROM THIS FEATURE AND ENHANCE CONVECTIVE POTENTIAL ACROSS BROAD
WARM SECTOR THROUGH THE PERIOD.  MODELS HAVE NOT HANDLED THESE
FEATURES WELL THE PAST DAY OR SO...BUT THESE COULD IMPACT HOW SEVERE
THREAT UNFOLDS TODAY.  ONE SUCH DISTURBANCE HAS ENHANCED ONGOING
STRONG/SEVERE THUNDERSTORMS NOW OVER THE MID SOUTH INTO THE LOWER OH
RIVER VALLEY...WHICH IS EXPECTED TO CONTINUE LIFTING NEWD ACROSS
PORTIONS OF KY/IND/OH THROUGH THE DAY WITH POTENTIAL FOR ISOLATED
LARGE HAIL.

SURFACE PATTERN WILL REMAIN COMPLICATED BY EARLIER CONVECTION...
THOUGH A COLD FRONT WILL BECOME ESTABLISHED ACROSS ERN PORTIONS OF
THE CENTRAL/SRN PLAINS THIS AFTERNOON...WHICH WILL MOVE SEWD ACROSS
THE GREAT LAKES/MID MS RIVER VALLEY OVERNIGHT. IN ADDITION...A WARM
FRONT WILL LIKELY BECOME BETTER FOCUSED ESEWD FROM A LOW CENTER NEAR
THE NRN MS RIVER VALLEY INTO THE SRN GREAT LAKES.  OUTFLOW BOUNDARY
FROM ONGOING CLUSTER OF STORMS OVER THE LOWER OH RIVER VALLEY MAY
DELAY OR RE-FOCUS THIS FEATURE FARTHER SOUTH INTO CENTRAL IL/SRN IA.
 ANOTHER...OUTFLOW BOUNDARY MAY ALSO REMAIN IN PLACE FROM THE LOWER
OH RIVER VALLEY ACROSS CENTRAL/NRN AR INTO SWRN MO THROUGH THE DAY. 
THOUGH THESE FEATURES MAY INHIBIT ROBUST MOISTURE RETURN NORTH OF
OZARKS/MID MS RIVER VALLEY...RICH GULF MOISTURE WILL REMAIN IN PLACE
TO THE SOUTH OVER ERN OK INTO THE MID SOUTH WITH SURFACE DEW POINTS
AOA 65F.  REGARDLESS...BOUNDARY LAYER MOISTURE WILL REMAIN MORE THAN
ADEQUATE FOR MODEST INSTABILITY AND POTENTIALLY SEVERE THUNDERSTORMS
ALONG AND AHEAD OF APPROACHING COLD FRONT FROM THE UPPER MID WEST
INTO THE SRN PLAINS BY LATER TODAY.

CAPPING MAY BE PROBLEMATIC OVER MUCH OF THE REGION TODAY UNDER A
RELATIVELY STRONG ELEVATED-MIXED LAYER NOW IN PLACE OVER THE PLAINS.
 HOWEVER...COMBINATION OF HEATING AND CONVERGENCE SHOULD SUPPORT
RAPID THUNDERSTORM DEVELOPMENT BETWEEN 18Z-21Z ALONG AND AHEAD OF
THE FRONT.  SHEAR WILL REMAIN MORE THAN ADEQUATE FOR SUPERCELLS AND
LINES AS ACTIVITY INTENSIFIES THROUGH THE LATE
AFTERNOON/EVENING...WITH SEVERE THREAT SPREADING EWD THROUGH THE
REMAINDER OF THE PERIOD.

THE MOST INTENSE SEVERE THUNDERSTORMS MAY REMAIN CONFINED TO GREATER
MOISTURE/INSTABILITY FROM FAR ERN/SERN OK AND POSSIBLY NERN TX
ACROSS AR...AND WE HAVE PLACED GREATEST SEVERE RISK AND HIGHEST
PROBABILITIES ACCORDINGLY.  HERE...FORECAST SOUNDINGS YIELD A
DANGEROUS COMBINATION OF CAPE AND SHEAR /MLCAPE GREATER THAN 2000
J/KG AND EFFECTIVE SHEAR IN EXCESS OF 60 KT/...WHICH WILL LIKELY
SUPPORT TORNADIC SUPERCELLS SHOULD CAP BREAK AS EXPECTED.  IN
ADDITION...STORM MODE IS EXPECTED TO REMAIN DISCRETE WITH SUBSEQUENT
ENHANCED RISK OF TORNADOES GIVEN FORECAST 200+ M2/S2 0-1 KM SRH AND
LOW LCL HEIGHTS.

...SRN CA...
VERY COLD STORM SYSTEM CONTINUES TO REMAIN ALONG THE WEST
COAST...WITH STRONG LOW LEVEL SHEAR AND STEEP LAPSE RATES EXPECTED
NEAR THE SRN CA COAST. STORMS PRODUCED MARGINALLY SEVERE HAIL AND
EVEN A BRIEF TORNADO ON FRIDAY.  INSTABILITY MAY BE GREATER
TODAY...AND THEREFORE EXPECT ANOTHER ACTIVE PERIOD WITH STRONGER
CORES PRODUCING WATERSPOUTS/TORNADOES AND LARGE HAIL INTO THE EARLY
EVENING.

..EVANS/GRAMS.. 03/11/2006