SWODY3
SPC AC 020712
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0212 AM CDT TUE OCT 02 2007
VALID 041200Z - 051200Z
..THERE IS A SLGT RISK OF SVR TSTMS THU AFTN AND EARLY THU EVE
ACROSS PARTS OF THE SRN PLATEAU....
..THERE IS A SLGT RISK OF SVR TSTMS LATE THU NIGHT ACROSS PARTS OF
THE NRN PLAINS....
..SYNOPSIS...
MODELS INDICATE THAT THE AMPLIFICATION OF THE LARGE-SCALE PATTERN
COMMENCING LATE WEDNESDAY WILL CONTINUE THROUGH THURSDAY...WITH A
LARGE POLAR TROUGH DIGGING INTO THE WESTERN STATES...AND A
DOWNSTREAM EASTERN STATES RIDGE BUILDING NORTHWARD THROUGH THE ST.
LAWRENCE VALLEY/NORTHERN NEW ENGLAND. JUST AHEAD OF THE POLAR
TROUGH...GUIDANCE SUGGESTS THAT A SIGNIFICANT SUBTROPICAL IMPULSE
WILL DEVELOP NORTHEASTWARD...INLAND ACROSS NORTHERN BAJA THROUGH THE
SOUTHERN PLATEAU/SOUTHERN ROCKIES. THIS IS EXPECTED TO BE
ACCOMPANIED BY A SUBSTANTIAL INFLUX OF MOISTURE INTO THE FOUR
CORNERS STATES. A RETURN FLOW OF MOISTURE WILL ALSO LIKELY OCCUR
FROM THE SOUTHERN THROUGH NORTHERN PLAINS...IN ASSOCIATION WITH
SURFACE CYCLOGENESIS TO THE LEE OF THE NORTH CENTRAL ROCKIES.
MEANWHILE...CONSIDERABLE DISPARITY EXISTS AMONG THE MODELS
CONCERNING THE POSSIBLE SUBTROPICAL/TROPICAL SYSTEM OVER THE GULF OF
MEXICO. BUT...GUIDANCE INDICATES A GENERAL WEAKENING OF THE SURFACE
LOW AS IT APPROACHES WESTERN/CENTRAL GULF COASTAL AREAS LATE
THURSDAY NIGHT/EARLY FRIDAY.
..CENTRAL/SRN GREAT BASIN AND ROCKIES...
IT SEEMS PROBABLE THAT GREATER LOW-LEVEL MOISTENING WILL OCCUR AHEAD
OF THE SUBTROPICAL IMPULSE THAN SUGGESTED BY THE NAM. AND...THE
EVOLVING UPPER PATTERN IS EXPECTED TO SUPPORT THE DEVELOPMENT OF A
CONVECTIVELY UNSTABLE STRATIFICATION ACROSS THE SOUTHERN
PLATEAU...PARTICULARLY ACROSS PARTS OF CENTRAL/SOUTHEAST
ARIZONA...WHERE SIZABLE CAPE IN EXCESS OF 1000 J/KG IS ALSO
EXPECTED.
BY PEAK HEATING THURSDAY AFTERNOON...LARGE-SCALE FORCING AND
DESTABILIZATION ARE EXPECTED TO SUPPORT SCATTERED THUNDERSTORMS FROM
THE LOWER DESERTS NORTHEASTWARD INTO THE MOGOLLON RIM. WITH
MODERATELY STRONG SOUTHWESTERLY MID/UPPER FLOW CONTRIBUTING TO
FAVORABLE DEEP LAYER SHEAR FOR UPDRAFT ROTATION...A FEW SUPERCELLS
ARE POSSIBLE...PRIMARILY WITH THE RISK FOR LARGE HAIL AND LOCALLY
DAMAGING WIND GUSTS. THE THREAT SHOULD CONTINUE INTO EARLY THURSDAY
EVENING...BEFORE DIMINISHING AS STABILIZATION OCCURS WITH THE LOSS
OF DAYTIME HEATING.
ACROSS THE EASTERN GREAT BASIN INTO WESTERN COLORADO...THE MAGNITUDE
OF MOISTENING AND DESTABILIZATION IS MORE UNCERTAIN AT THE PRESENT
TIME. BUT...DEEP LAYER SHEAR WILL LIKELY BE SUFFICIENT FOR UPDRAFT
ROTATION IN ANY SUSTAINED CONVECTIVE DEVELOPMENT.
..PLAINS...
A WARM MID-LEVEL ENVIRONMENT IS EXPECTED TO CAP RETURNING MOISTURE
THROUGH MUCH OF THE CENTRAL PLAINS THURSDAY. HOWEVER...BY LATE
THURSDAY NIGHT...FORCING ON THE NOSE OF A 50+ KT SOUTHERLY LOW-LEVEL
JET...ALONG THE FRONTAL ZONE EAST NORTHEAST OF THE DEEPENING SURFACE
LOW...AND BENEATH THE INFLECTION BETWEEN THE UPSTREAM TROUGH AND THE
DOWNSTREAM RIDGE...WILL FAVOR CONVECTIVE DEVELOPMENT. INITIATION IS
EXPECTED AS A RAPID MOISTENING ABOVE THE FRONTAL INVERSION SUPPORTS
MOST UNSTABLE CAPE OF 1000-2000 J/KG. THE STRONGEST STORMS WILL BE
CAPABLE OF PRODUCING LARGE HAIL...ENHANCED BY STRONG DEEP LAYER
SHEAR IN THE CONVECTIVE LAYER. A FEW SUPERCELLS ARE POSSIBLE.
.KERR.. 10/02/2007
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