[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 040556
SWODY1
SPC AC 040554

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT THU MAY 04 2006

VALID 041200Z - 051200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN/EVE FROM THE ARKLATEX
EASTWARD INTO THE TENNESSEE VALLEY....

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN/EVE ACROSS PARTS OF
THE SRN PLAINS....

MODELS INDICATE THAT BROAD TROUGHING WILL PERSIST THROUGH THIS
FORECAST PERIOD IN THE NORTHERN BRANCH OF THE POLAR WESTERLIES...AND
EXPAND EASTWARD FROM THE UPPER MIDWEST/EAST CENTRAL CANADIAN
PROVINCES TOWARD THE CANADIAN MARITIMES/NORTH ATLANTIC COAST.  AS
THIS OCCURS...IMPULSES ARE PROGGED TO CONSOLIDATE IN UPSTREAM
SOUTHERN BRANCH TROUGH ACROSS THE INTERMOUNTAIN WEST. 
EVENTUALLY...A CLOSED MID-LEVEL CIRCULATION IS EXPECTED TO EVOLVE
OVER THE GREAT BASIN...AND TROUGHING TO THE SOUTH OF THIS FEATURE
WILL COME INCREASINGLY IN PHASE WITH THE SUBTROPICAL STREAM.

DOWNSTREAM OF THE SOUTHERN ROCKIES THROUGH THE SOUTH ATLANTIC COAST
STATES...MID/UPPER FLOW REGIME WILL REMAIN WEAK...BETWEEN CONFLUENT
BELTS OF POLAR WESTERLIES AND THE SUBTROPICAL STREAM. 
HOWEVER...WITH THE UPPER PATTERN SUPPORTING SOUTHWARD BUILDING
SURFACE RIDGE OUT OF CANADA TO THE LEE OF THE ROCKIES...
MOIST...POTENTIALLY UNSTABLE AIR WILL BECOME GENERALLY CONFINED TO
THIS REGION.  FRONT WILL JUST BE ADVANCING INTO THE LOWER OHIO
VALLEY AND LOWER GREAT LAKES REGION AT 12Z...BUT SIGNIFICANT
MOISTURE RETURN IN WAKE OF PRIOR FRONTAL PASSAGE TO THE LEE OF THE
APPALACHIANS AND ASSORTMENT OF OUTFLOW BOUNDARIES ACROSS THE
TENNESSEE VALLEY IS NOT ANTICIPATED.

...ARKLATEX THRU NRN GULF STATES/TENNESSEE VALLEY...
CONSIDERABLE UNCERTAINTY EXISTS ACROSS THIS AREA CONCERNING DETAILS
OF CONVECTIVE DEVELOPMENT.  BUT...FRONTAL ZONE ADVANCING SOUTH OF
THE LOWER OHIO VALLEY AND OZARK PLATEAU...AND FRONTAL ZONE/OUTFLOW
BOUNDARIES EXTENDING ACROSS THE SOUTHERN APPALACHIANS INTO THE
TENNESSEE VALLEY...WILL PROVIDE FOCUS FOR INITIATION OF STORMS. 
THIS SEEMS LIKELY TO OCCUR AS EARLY AS MID DAY AS HEATING ERODES
RELATIVELY WEAK INHIBITION.  THOUGH SHEAR/FLOW WILL BE WEAK...MIXED
LAYER CAPE OF 1500 TO 2000 J/KG BY PEAK HEATING WILL BE SUFFICIENT
FOR A FEW VIGOROUS UPDRAFTS WITH DAMAGING WIND GUSTS AND SOME HAIL. 
A CONVECTIVELY GENERATED MID-LEVEL CYCLONIC VORTICITY CENTER COULD
PROVIDE A FOCUS FOR ANOTHER CLUSTER OF STORMS ACROSS THE ARKLATEX
INTO THE NORTH CENTRAL GULF STATES THIS EVENING INTO THE OVERNIGHT
HOURS.

...SOUTHERN PLAINS...
LARGE CONVECTIVE CLUSTER IS EXPECTED TO WEAKEN EARLY IN THE DAY
ACROSS THE RED RIVER VALLEY/NORTHERN TEXAS.  OUTFLOW BOUNDARY
GENERATED BY THIS FEATURE...AND SURFACE FRONT ADVANCING INTO
NORTHERN/NORTHWEST TEXAS...ARE THEN EXPECTED TO PROVIDE FOCUS FOR
NEW ACTIVITY.  THIS MOST LIKELY WILL NOT OCCUR UNTIL VERY LATE IN
THE AFTERNOON OR EVENING...AS STABILIZING INFLUENCE OF EARLY
ACTIVITY WANES AND LARGE-SCALE ASCENT INCREASES WITH SUBTROPICAL
STREAM IMPULSE/JET STREAK.  GIVEN CONTINUING PRESENCE OF MOIST
BOUNDARY LAYER AND STEEP MID-LEVEL LAPSE RATES...MIXED LAYER CAPE OF
2000 TO 3000 J/KG IS EXPECTED BY PEAK HEATING. THIS ENVIRONMENT
WILL BE SUPPORTIVE OF BOTH INTENSE UPDRAFTS AND DOWNDRAFTS...WITH
POTENTIAL FOR LARGE HAIL/DAMAGING WIND GUSTS.  MODELS SUGGEST A WEAK
TO MODERATE SOUTHERLY LOW-LEVEL JET DEVELOPING INTO THE TEXAS HILL
COUNTRY BY THIS EVENING...WHICH COULD PROVIDE SUPPORT FOR ANOTHER
LARGE MESOSCALE CONVECTIVE SYSTEM.

...OHIO VALLEY INTO THE LOWER GREAT LAKES...
MOISTURE RETURN WILL BE LIMITED AHEAD OF FRONT ADVANCING EAST OF THE
LOWER GREAT LAKES.  THIS IS EXPECTED TO CONFINE CAPE TO VALUES AT OR
BELOW 500 J/KG...BUT FORCING ON TAIL END OF FAIRLY VIGOROUS SHORT
WAVE TROUGH IS EXPECTED TO BE SUFFICIENT FOR SCATTERED THUNDERSTORMS
THIS AFTERNOON ACROSS PARTS OF NEW YORK/ PENNSYLVANIA. THOUGH
UPDRAFTS SHOULD BE WEAK...DEEP MIXED BOUNDARY LAYER WITH SIZABLE
TEMPERATURE/DEW POINT SPREADS IN PRESENCE OF WEAK TO MODERATE MEAN
FLOW COULD SUPPORT LOCALLY DAMAGING WIND GUSTS.  THOUGH FORCING WILL
BE WEAKER...WIDELY SCATTERED STORMS COULD DEVELOP WESTWARD ALONG
FRONT INTO PARTS OF THE LOWER OHIO VALLEY BY EARLY EVENING...WHERE
THERMODYNAMIC ENVIRONMENT MAY BE MORE FAVORABLE FOR HAIL NEAR SEVERE
LIMITS.

...GREAT BASIN...
FRONTAL ZONE ACROSS SOUTH CENTRAL UTAH INTO WEST CENTRAL COLORADO IS
EXPECTED TO AGAIN BE A FOCUS FOR WIDELY SCATTERED LATE AFTERNOON
STORMS.  MOISTURE IS LIMITED...BUT VERY STEEP LAPSE RATES BENEATH
COLD MID-LEVEL TROUGH WILL PROVIDE AT LEAST SOME POTENTIAL FOR
HAIL/WIND GUSTS APPROACHING/BRIEFLY EXCEEDING SEVERE LIMITS.

..KERR/GRAMS.. 05/04/2006