DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 230732
SWODY3
SPC AC 230730

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0230 AM CDT MON JUL 23 2007

VALID 251200Z - 261200Z

..THERE IS A SLGT RISK OF SVR TSTMS WED/WED NIGHT ACROSS PARTS OF
THE NRN PLAINS....

..SYNOPSIS...
MODELS INDICATE THAT AN INCREASINGLY ZONAL BELT OF POLAR WESTERLIES
WILL REMAIN NORTH OF THE CANADIAN/U.S. BORDER WEDNESDAY/WEDNESDAY
NIGHT...WITH SEVERAL EMBEDDED PROGRESSIVE SHORT WAVE TROUGHS. ONE
OF THESE IS PROGGED TO APPROACH THE BRITISH COLUMBIA COAST...WHILE
ANOTHER CONTINUES EASTWARD ACROSS PARTS OF MANITOBA/ONTARIO AND
HUDSON BAY. THE LATTER FEATURE MAY CONTRIBUTE TO SOME
NORTH/NORTHWESTWARD ACCELERATION OF THE CLOSED LOW OVER THE OHIO
VALLEY/GREAT LAKES REGION...BUT THE LOW IS EXPECTED TO REMAIN
GENERALLY CUT-OFF FROM THE WESTERLIES THROUGH THIS FORECAST PERIOD
AND BEYOND. SUBTROPICAL RIDGING IS PROGGED TO CONTINUE TO BUILD
WESTWARD INTO THE ATLANTIC SEABOARD...AND NORTHWARD THROUGH THE
SOUTHEAST STATES. AND...RIDGING WILL PERSIST ACROSS MUCH OF THE
INTERMOUNTAIN WEST AND ROCKIES...THOUGH IN A WEAKENED STATE...DUE TO
THE CENTRAL CANADIAN SHORT WAVE TROUGH...AND WEAKER IMPULSES
PROGRESSING AROUND ITS PERIPHERY.

..NORTHERN PLAINS...
A FRONTAL ZONE ASSOCIATED WITH THE CENTRAL CANADIAN SHORT WAVE
TROUGH IS PROGGED TO ADVANCE EAST OF THE NORTHERN ROCKIES...INTO THE
NORTHERN PLAINS...BEFORE STALLING WEDNESDAY NIGHT. IN ADVANCE OF
THE FRONT...STRONG HEATING IS EXPECTED ACROSS THE NORTH CENTRAL HIGH
PLAINS...AND ALONG AN AXIS ACROSS WESTERN SOUTH DAKOTA INTO
SOUTHWEST/SOUTH CENTRAL NORTH DAKOTA BY LATE WEDNESDAY AFTERNOON.
THIS PROBABLY WILL PROVIDE THE FOCUS FOR SIGNIFICANT
DESTABILIZATION...WITH A DEEPLY MIXED BOUNDARY LAYER FORMING WITH
SUFFICIENT MOISTURE FOR MIXED LAYER CAPE OF 1500-3000 J/KG.

SHORTLY AFTER PEAK HEATING...MODELS ARE SUGGESTIVE THAT ENOUGH
WEAKENING OF A CAPPING MID-LEVEL THERMAL RIDGE WILL OCCUR TO ALLOW
INITIATION OF CONVECTIVE DEVELOPMENT. FLOW FIELDS AND DEEP LAYER
SHEAR WILL LIKELY BE WEAK...BUT THE THERMODYNAMIC ENVIRONMENT SHOULD
BE SUPPORTIVE OF SEVERE STORMS...WITH DAMAGING WIND GUSTS THE
PRIMARY THREAT...ALONG WITH A RISK FOR LARGE HAIL. ACTIVITY IS
EXPECTED TO PERSIST INTO THE EVENING HOURS...BEFORE WEAKENING WITH
LOSS OF DAYTIME HEATING. THEN...MODELS INDICATE AN INCREASE IN
STORMS COULD OCCUR ALONG/NORTH OF THE FRONTAL ZONE...FROM SOUTHWEST
TO NORTHEAST...ACROSS MUCH OF CENTRAL NORTH DAKOTA LATE WEDNESDAY
EVENING/WEDNESDAY NIGHT. AND...ENOUGH CAPE IS EXPECTED TO EXIST IN
A MOISTENING LAYER ABOVE FRONTAL INVERSION...AT LEAST IN A NARROW
CORRIDOR...FOR A CONTINUING RISK OF LARGE HAIL.

.KERR.. 07/23/2007

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