[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 070602
SWODY1
SPC AC 070601

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0101 AM CDT FRI APR 07 2006

VALID 071200Z - 081200Z

...THERE IS A HIGH RISK OF SVR TSTMS TODAY ACROSS MUCH OF NRN
MS...NRN AL...AND PARTS OF SRN TN.  THIS INCLUDES THE MEMPHIS
TN/TUPELO MS AREAS EASTWARD INTO BIRMINGHAM AL AND CHATTANOOGA
...WHICH SEEMS LIKELY TO BE AT THE FOCUS FOR AN OUTBREAK OF SEVERE
THUNDERSTORMS...INCLUDING THE RISK FOR SUPERCELLS WITH TORNADOES....

...THERE IS A MDT RISK OF SVR TSTMS TODAY INTO TONIGHT THROUGH A
LARGE PORTION OF THE LOWER MISSISSIPPI VALLEY THROUGH THE TN VLY/SRN
APPALACHIANS....

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE AND
HIGH RISK AREAS...ACROSS MUCH OF THE NATION EAST OF THE MS RIVER
INTO THE APPALACHIANS....

THE LARGE-SCALE UPPER FLOW PATTERN HAS BECOME A BIT LESS
PROGRESSIVE...BUT MODELS INDICATE THAT THE CENTRAL PLAINS CLOSED LOW
WILL GRADUALLY EVOLVE INTO AN OPEN WAVE AND TURN SOUTHEASTWARD
TODAY...LIKELY ADVANCING THROUGH MUCH OF THE LOWER MISSISSIPPI
VALLEY BY 12Z SATURDAY.  THIS IS FORECAST IN RESPONSE TO A
SIGNIFICANT SMALLER SCALE IMPULSE ROTATING AROUND ITS
SOUTHWESTERN/SOUTHERN PERIPHERY...AND FORCING ASSOCIATED WITH A
NORTHERN STREAM TROUGH...WHICH WILL DIG THROUGH THE GREAT LAKES
REGION.

AS THIS OCCURS...A BROAD BELT OF STRONG CYCLONIC MID/UPPER FLOW IS
PROGGED TO CONTINUE TO GRADUALLY OVERSPREAD MUCH OF THE GULF COAST
STATES AND MID SOUTH INTO THE NORTHEAST.  STRENGTHENING WIND
FIELDS/SHEAR PROFILES WILL BECOME JUXTAPOSED WITH A RETURN FLOW OF
BOUNDARY LAYER MOISTURE FROM THE WESTERN GULF OF MEXICO...THROUGH A
BROAD AREA FROM THE LOWER/MIDDLE MISSISSIPPI VALLEY INTO THE
APPALACHIANS.  THIS IS EXPECTED TO SUPPORT INCREASING CONVECTIVE
POTENTIAL...INCLUDING RISK FOR SEVERE STORMS...WHICH COULD BECOME
FAIRLY NUMEROUS AND INTENSE BY THE AFTERNOON/EVENING HOURS.

OTHER THUNDERSTORM ACTIVITY APPEARS POSSIBLE INTO CENTRAL PACIFIC
COASTAL AREAS. APPROACHING UPPER TROUGH IS FORECAST TO GENERALLY
REMAIN OFFSHORE...BUT MODELS INDICATE A FAIRLY SIGNIFICANT IMPULSE
WILL PIVOT AROUND ITS EASTERN PERIPHERY...ACROSS THE CALIFORNIA
COAST THROUGH THE SIERRA NEVADA BY THE END OF THE FORECAST PERIOD.

...LOWER MISSISSIPPI VALLEY THROUGH SOUTHERN APPALACHIANS...
MODELS SUGGEST LEADING EDGE OF MID-LEVEL COOLING ASSOCIATED WITH THE
PLAINS SYSTEM WILL OVERSPREAD MUCH OF THE REGION BY MID DAY.  THIS
WILL WEAKEN INHIBITION...AND SURFACE HEATING MAY BE ENOUGH TO
INITIATE AT LEAST SCATTERED VIGOROUS CONVECTIVE DEVELOPMENT AS
BOUNDARY LAYER DEW POINTS CLIMB THROUGH THE 60S.

AS MIXED LAYER CAPE INCREASES IN EXCESS OF 2000 J/KG...STRONG DEEP
LAYER SHEAR WILL BE SUPPORTIVE OF SUPERCELLS.  CONFLUENT REGIME
ASSOCIATED WITH 30 TO 40 KT SOUTHWESTERLY LOW-LEVEL JET SEEMS A
LIKELY FOCUS FOR ACTIVITY...FROM PARTS OF CENTRAL/SOUTHERN
MISSISSIPPI THROUGH EASTERN TENNESSEE. SOME OF THESE SUPERCELLS MAY
BECOME LONG-LIVED...AND MODELS SUGGEST SUBSTANTIALLY LARGE/CLOCKWISE
CURVED HODOGRAPHS ALONG THIS AXIS TO SUPPORT POTENTIAL FOR A FEW
STRONG TORNADOES.

WITH THE APPROACH OF DIGGING UPPER TROUGH...STRENGTHENING MID/UPPER
FORCING IS EXPECTED TO SUPPORT INCREASINGLY WIDESPREAD SEVERE
THUNDERSTORMS FROM THE LOWER MISSISSIPPI VALLEY INTO MIDDLE
TENNESSEE LATE THIS AFTERNOON INTO THE EVENING HOURS.  ACTIVITY MAY
BE SLOW TO WEAKEN AS STRONGER FORCING SHIFTS TOWARD THE SOUTHERN
APPALACHIANS OVERNIGHT.

...OHIO VALLEY...
DEFORMATION ZONE BETWEEN NORTHERN AND SOUTHERN STREAM IMPULSES
APPEARS TO BE A LIKELY FOCUS FOR CONVECTIVE DEVELOPMENT TODAY. 
MODELS SUGGEST FAIRLY STRONG SURFACE HEATING WILL OCCUR ALONG AN
AXIS FROM THE ST. LOUIS AREA EASTWARD THROUGH SOUTHERN OHIO... WHICH
SHOULD SUPPORT WEAK TO MODERATE DESTABILIZATION AHEAD OF
DEVELOPING/STRENGTHENING BAROCLINIC ZONE.  FRONTAL ZONE IS PROGGED
TO SURGE SOUTH OF THE GREAT LAKES REGION EARLY THIS AFTERNOON...
THROUGH MUCH OF THE OHIO VALLEY BY EARLY EVENING.  THIS FORCING IS
EXPECTED TO BECOME SUFFICIENT FOR AN EVOLVING SQUALL LINE...WITH
MIXED LAYER CAPE ON THE ORDER OF 1000 J/KG SUPPORTIVE OF VIGOROUS
UPDRAFTS IN STRONG AND SHEARED WESTERLY FLOW.  IN ADDITION TO LARGE
HAIL...DAMAGING WIND GUSTS COULD BECOME FAIRLY NUMEROUS BY/ SHORTLY
AFTER PEAK HEATING.

..KERR/CROSBIE.. 04/07/2006