SWODY2
SPC AC 250544
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1244 AM CDT WED JUL 25 2007
VALID 261200Z - 271200Z
..THERE IS A SLGT RISK OF SVR TSTMS THU AFTN/EVE FROM PARTS OF THE
MID MO VALLEY INTO THE UPR MS VLY....
..SYNOPSIS..
THE STRONGER WESTERLIES ARE EXPECTED TO REMAIN CONFINED TO THE
HIGHER LATITUDES THROUGH THIS FORECAST PERIOD...WITH SEVERAL SHORT
WAVE TROUGHS EMBEDDED WITHIN THE GENERALLY ZONAL BELT EXTENDING
ACROSS CANADA. BUT...MODELS INDICATE THAT...AS ONE OF THESE
IMPULSES REMAINS PROGRESSIVE ACROSS THE CENTRAL INTO EASTERN
CANADIAN PROVINCES...AN UPPER RIDGE AXIS OVER THE NORTHERN
PLAINS/UPPER MISSISSIPPI VALLEY WILL BREAK DOWN BY EARLY
THURSDAY...AND THE CUT-OFF LOW OVER THE GREAT LAKES/OHIO VALLEY WILL
FINALLY BEGIN TO ACCELERATE EASTWARD LATER THURSDAY INTO EARLY
FRIDAY. ELSEWHERE...SUBTROPICAL RIDGING LIKELY WILL PERSIST ACROSS
THE EASTERN GULF/SOUTH ATLANTIC COAST STATES...WITH THE CENTER OF
THE WESTERN RIDGE CONTINUING TO SLOWLY SHIFT SOUTHWEST OF THE FOUR
CORNERS REGION. IN BETWEEN...A WEAK UPPER TROUGH OR ELONGATED
CIRCULATION IS EXPECTED TO LINGER OVER TEXAS AND THE NORTHEASTERN
MEXICAN PLATEAU.
..CENTRAL/SOUTHERN HIGH PLAINS INTO THE UPPER GREAT LAKES...
A FRONTAL ZONE ACCOMPANYING THE CANADIAN SHORT WAVE TROUGH IS
PROGGED TO ADVANCE SOUTHEASTWARD INTO THE UPPER MISSISSIPPI VALLEY
/MID MISSOURI VALLEY AND CENTRAL PLAINS BY LATE THURSDAY AFTERNOON.
STRONG HEATING IS EXPECTED IN A NARROW CORRIDOR AHEAD OF THE
FRONT...AND THIS SHOULD CONTRIBUTE TO THE DEVELOPMENT OF A
HOT...DEEP MIXED BOUNDARY LAYER WITH WEAK TO MODERATE CAPE.
THE STRONGEST DESTABILIZATION IS ANTICIPATED ROUGHLY ALONG AN AXIS
FROM SOUTHEASTERN SOUTH DAKOTA THROUGH NORTHEASTERN MINNESOTA/
NORTHWESTERN WISCONSIN...WHERE SURFACE DEW POINTS APPEAR LIKELY TO
REMAIN AT OR ABOVE 70F. THIS IS FORECAST TO CONTRIBUTE TO MIXED
LAYER CAPE OF 1500-3000 J/KG BY OR SHORTLY AFTER PEAK HEATING.
AND...IN CONJUNCTION WITH FRONTAL FORCING...PERHAPS WEAK MID/UPPER
FORCING...THUNDERSTORM ACTIVITY IS EXPECTED TO FORM...POSSIBLY
EVOLVING INTO A BROKEN LINE OF STORMS BY EARLY EVENING. THOUGH WIND
FIELDS/DEEP LAYER SHEAR WILL BE MOSTLY WEAK...THERMODYNAMIC PROFILES
WILL FAVOR POTENTIAL FOR A FEW SEVERE STORMS WITH DAMAGING
WINDS...PERHAPS SOME MARGINALLY SEVERE HAIL...BEFORE CONVECTION
WEAKENS/DEVELOPS SOUTHEASTWARD THURSDAY NIGHT.
OTHER SCATTERED STORMS ARE POSSIBLE IN A MORE DEEPLY MIXED BOUNDARY
LAYER ACROSS NEBRASKA INTO THE CENTRAL/SOUTHERN HIGH PLAINS. AN
ADDITIONAL SMALL CLUSTER OR TWO OF STORMS MAY ACCOMPANY A WEAKENING
IMPULSE...NOW SHIFTING ACROSS THE MID MISSOURI VALLEY...AS IT
CONTINUES SOUTHWARD THROUGH THE SOUTH CENTRAL PLAINS THURSDAY.
..SOUTHERN PLATEAU...
AS THE UPPER HIGH CENTER GRADUALLY SHIFTS SOUTH OF THE FOUR CORNERS
REGION...STEERING FLOW WILL BE WEAK. BUT...MODEL FORECAST SOUNDINGS
ARE SUGGESTIVE OF FAVORABLE PROFILES FOR AT LEAST SLOW PROPAGATION
OF CONVECTIVE ACTIVITY OFF THE MOUNTAINS INTO THE LOWER DESERTS
THURSDAY. THE MAGNITUDE OF THE MOISTURE RETURN FROM THE GULF OF
CALIFORNIA...IN THE WAKE OF A WAVE LIFTING NORTHWEST OF SOUTHERN
BAJA...IS STILL IN QUESTION. BUT...ENOUGH HEATING/ DESTABILIZATION
IS EXPECTED ACROSS THE LOWER DESERTS TO SUPPORT AT LEAST A RISK FOR
LOCALIZED DOWNBURSTS...PERHAPS SOME HAIL.
..LOWER GREAT LAKES/OHIO VALLEY...
GIVEN RELATIVELY COOL AIR ALOFT...ENOUGH HEATING IS EXPECTED TO
SUPPORT WEAK TO...PERHAPS...MODERATE DESTABILIZATION AHEAD OF SLOWLY
EASTWARD ACCELERATING CLOSED LOW. 20-30 KT SOUTHWESTERLY LOWER/MID
TROPOSPHERIC FLOW MAY CONTRIBUTE TO MODERATE STORM MOTIONS...AND
SOME RISK FOR GUSTY WINDS WHICH MAY APPROACH SEVERE LIMITS. SOME
MARGINALLY SEVERE HAIL WILL ALSO BE POSSIBLE.
.KERR.. 07/25/2007
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