SPC AC 061123
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0623 AM CDT FRI JUL 06 2007
VALID 071200Z - 081200Z
...NO SVR TSTM AREAS FORECAST...
CORRECTED GENERAL TSTM LINES
...SYNOPSIS...
MODELS CONTINUE TO INDICATE FURTHER DE-AMPLIFICATION OF UPPER FLOW
PATTERN WITH ZONAL FLOW EXPECTED TO DEVELOP ALONG THE NRN TIER OF
STATES...AS UPPER TROUGH MOVING THROUGH THE NERN STATES ON DAY 1
REMAINS PROGRESSIVE TRACKING TOWARD THE CANADIAN MARITIMES ON
SATURDAY. THE NAM REMAINS THE MORE AMPLIFIED WITH UPSTREAM SHORT
WAVE TROUGH...NOW APPROACHING BC COAST...AS THIS FEATURE MOVES ESEWD
FROM AB/SK TO SRN MB/WRN ONTARIO AND ADJACENT NORTH CENTRAL STATES
DURING DAY 2.
DESPITE THESE UPPER LEVEL DIFFERENCES...MODELS TEND TO AGREE IN THE
LOW LEVELS WITH A COLD FRONT MOVING SWD INTO THE NRN PLAINS AND
UPPER MS VALLEY.
...NRN PLAINS INTO UPPER GREAT LAKES...
IN ADDITION TO MODEL DIFFERENCES IN THE UPPER LEVELS...THERE ARE
MODEL UNCERTAINTIES IN THE AMOUNT OF LOW LEVEL MOISTURE THAT RETURNS
NWD INTO ERN ND/NWRN MN ON SATURDAY...WITH THE NAM/NAMKF SUGGESTING
THE GREATEST MOISTURE RETURN. INCREASING ZONAL MID LEVEL WIND
COMPONENT WILL RESULT IN EWD ADVECTION OF ELEVATED MIXED LAYER INTO
THIS REGION...ATOP AN INCREASINGLY MOIST BOUNDARY LAYER WITH AIR
MASS BECOMING MODERATELY TO POTENTIALLY VERY UNSTABLE AHEAD OF FRONT
BY SATURDAY AFTERNOON. MODEL FORECAST SOUNDINGS SHOW A FAIRLY
STRONG CAP ACROSS WARM SECTOR AIR MASS WHICH WILL POTENTIALLY LIMIT
DIURNAL TSTM DEVELOPMENT AHEAD OF FRONT. NAM/NAMKF SOLUTIONS
CONTINUE TO DEVELOP DEEP CONVECTION AHEAD OF FRONT...DUE IN LARGE
PART TO THE STRONGER LARGE-SCALE FORCING FOR ASCENT ATTENDANT TO
MORE AMPLIFIED UPPER TROUGH OVER CENTRAL CANADA. THE LESS DYNAMIC
SOLUTION OF THE GFS CONTINUES TO SHOW THE CAP BEING MAINTAINED WITH
NO CONVECTIVE DEVELOPMENT. GIVEN THE CONTINUED UNCERTAINTY IN
LARGE-SCALE PATTERN EVOLUTION AND UNCERTAINTY IN CAP BREAKING FOR
STORMS TO DEVELOP WITHIN WARM SECTOR AIR MASS...PROBABILITY FOR
SEVERE STORMS REMAINS LOW.
...SRN MT/NRN WY...
POTENTIAL WILL EXIST FOR TSTMS TO DEVELOP IN POST-FRONTAL UPSLOPE
FLOW REGIME WHERE RESIDUAL LOW-LEVEL MOISTURE AND STEEP LAPSE RATES
WILL CONTRIBUTE TO POTENTIALLY MODERATE INSTABILITY. MODEL
UNCERTAINTIES EXIST WITH THE COVERAGE OF TSTMS THAT DEVELOP IN THIS
REGION...AND THUS WILL MAINTAIN LOW PROBABILITIES FOR SEVERE THREAT.
..PETERS.. 07/06/2007
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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