SPC AC 030532
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT WED OCT 03 2007
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS THU AFTN/EARLY THU EVE ACROSS
PARTS OF THE SRN PLATEAU....
...THERE IS A SLGT RISK OF SVR TSTMS THU NIGHT ACROSS PARTS OF THE
NRN PLAINS....
...SYNOPSIS...
WITHIN A STRONG CYCLONIC BELT OF POLAR WESTERLIES...NOW CURVING
ACROSS THE NORTHEAST PACIFIC INTO THE NORTHWESTERN U.S...A
SOUTHEASTWARD AMPLIFICATION APPEARS SLOWLY UNDERWAY. AND...MODELS
INDICATE THAT THIS WILL CONTINUE THROUGH THURSDAY/THURSDAY NIGHT.
BY 12Z FRIDAY...A LARGE UPPER TROUGH IS FORECAST TO ENCOMPASS MUCH
OF THE WESTERN STATES...WITH THE MOST SIGNIFICANT EMBEDDED SHORT
WAVE IMPULSE STILL DIGGING INTO THE GREAT BASIN. AT THE SAME TIME
...THE SOUTHEASTERN STATES RIDGE IS PROGGED TO BUILD NORTHWARD
THROUGH THE GREAT LAKES/ST. LAWRENCE VALLEY AND NEW ENGLAND.
JUST AHEAD OF THE POLAR TROUGH...THE GFS AND ECMWF STILL APPEAR
SIMILAR IN INDICATING THAT A SIGNIFICANT SUBTROPICAL IMPULSE WILL
ADVECT INLAND ACROSS NORTHERN BAJA...WITHIN THE SOUTHWESTERLY UPPER
FLOW REGIME...REACHING THE SOUTHERN PLATEAU BY PEAK HEATING
THURSDAY. A SIGNIFICANT INFLUX OF MOISTURE IS EXPECTED TO PRECEDE
THIS SYSTEM INTO THE FOUR CORNERS STATES. AND...A RETURN FLOW OF
LOW-LEVEL MOISTURE FROM THE SOUTHERN THROUGH NORTHERN PLAINS SHOULD
ALSO OCCUR...AS LEE SURFACE CYCLOGENESIS INITIATES IN RESPONSE TO
EVOLVING UPSTREAM PATTERN.
MEANWHILE...CONSIDERABLE DIFFERENCES CONTINUE TO EXIST AMONG THE
MODELS CONCERNING A POSSIBLE SUBTROPICAL/TROPICAL SYSTEM OVER THE
GULF OF MEXICO. BUT...GUIDANCE STILL GENERALLY INDICATES THAT AN
ASSOCIATED SURFACE LOW WILL TEND TO WEAKEN AS IT APPROACHES
CENTRAL/WESTERN GULF COASTAL AREAS LATE IN THE PERIOD.
...SOUTHERN PLATEAU...
MODEL FORECAST SOUNDINGS INDICATE SIGNIFICANT DESTABILIZATION BY
PEAK HEATING THURSDAY...PARTICULARLY ACROSS PARTS OF CENTRAL/
SOUTHERN ARIZONA...WHERE MIXED LAYER CAPE IN EXCESS OF 1000 J/KG
SEEMS LIKELY. AND...INCREASING LARGE-SCALE FORCING FOR UPWARD
VERTICAL MOTION IS EXPECTED TO SUPPORT THE INITIATION OF SCATTERED
THUNDERSTORMS...FROM THE LOWER DESERTS NORTHEASTWARD INTO THE
MOGOLLON RIM. EMBEDDED WITHIN A MODERATE TO STRONG SOUTHWESTERLY
MID/UPPER FLOW...DEEP LAYER SHEAR SHOULD BE MORE THAN SUFFICIENT FOR
UPDRAFT ROTATION...WITH A FEW SUPERCELLS POSSIBLE. THE RISK FOR
LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS WILL PROBABLY BE THE
PRIMARY SEVERE THREATS INTO THE EVENING HOURS...BEFORE STORMS
WEAKEN/DIMINISH WITH THE LOSS OF DAYTIME HEATING.
...PLAINS...
THE POSSIBILITY OF CONVECTIVE DEVELOPMENT ACROSS THE
CENTRAL/SOUTHERN PLAINS THURSDAY AFTERNOON IS STILL A BIT
UNCLEAR...DUE TO UNCERTAIN STRENGTH OF INHIBITION ASSOCIATED WITH A
FAIRLY WARM MID-LEVEL ENVIRONMENT. ISOLATED...RELATIVELY
SHORT-LIVED STORMS APPEAR POSSIBLE...MAINLY DURING THE 04/21Z-05/00Z
TIME FRAME. IF THIS OCCURS...THE BEST POTENTIAL FOR A SUPERCELL
APPEARS TO EXIST FROM A POSSIBLE DRY LINE/SURFACE WARM FRONT
INTERSECTION ACROSS NORTHWESTERN KANSAS...SOUTHWARD THROUGH WESTERN
KANSAS...IN PROXIMITY TO THE SUBTROPICAL JET AXIS.
OTHER...ISOLATED TO SCATTERED STORMS MAY OCCUR LATE THURSDAY
AFTERNOON/EVENING...ALONG A STRENGTHENING SOUTHERLY LOW-LEVEL JET
AXIS...FROM PARTS OF CENTRAL KANSAS THROUGH EASTERN NEBRASKA.
BUT...THE MODELS ARE STILL SUGGESTIVE THAT THE MOST SIGNIFICANT
CONVECTIVE DEVELOPMENT WILL NOT OCCUR UNTIL LATE THURSDAY NIGHT...
AS MOISTURE AND LARGE-SCALE ASCENT INCREASE ABOVE A LOWER/MID
TROPOSPHERIC BAROCLINIC ZONE NORTH AND EAST OF THE MID MISSOURI
VALLEY. MOST UNSTABLE CAPE REACHING 1000-2000 J/KG WITHIN A
STRONGLY SHEARED REGIME WILL BE FAVORABLE FOR A FEW SUPERCELLS...
PRIMARILY WITH THE RISK FOR LARGE HAIL.
..KERR.. 10/03/2007
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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