SPC AC 031742
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1242 PM CDT TUE JUL 03 2007
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ERN GREAT LAKES WSWWD
INTO THE MID MISSISSIPPI VALLEY....
...SYNOPSIS...
MID/UPPER AIR PATTERN MARKED BY HIGH AMPLITUDE RIDGE OVER THE WRN
U.S. WITH A TROUGH OVER JAMES BAY INTO THE GREAT LAKES AND PARTS OF
THE NERN U.S. MODELS SHOW SEVERAL EMBEDDED VORTICES TRAVELING
THROUGH THE TROUGH..WITH THE MAIN FEATURE MOVING FROM THE CENTRAL
GREAT LAKES EWD AND NEWD INTO NEW ENGLAND DURING THE PERIOD.
CURRENTLY...A SERIES OF CONVECTIVE BOUNDARIES ARE LAID OUT FROM
CENTRAL MN SWWD THRU E CENTRAL SD...THEN SWWD INTO N CENTRAL NEB.
THIS IS ASSOCIATED WITH ACTIVITY OUT AHEAD OF MAIN SYNOPTIC FRONTAL
BOUNDARY OVER THE NORTHERN PLAINS. THIS FRONT IS FORECAST TO BE
OVER THE UPPER GREAT LAKES AT THE START OF THE PERIOD AND EXTEND
SWWD THRU KS INTO ERN CO...FOLLOWING THE GFS SOLUTION AT THIS TIME
OVER THE NAM.
...LOWER GREAT LAKES SWWD INTO THE MID MS VALLEY...
THE MAIN CHALLENGE IS ESTIMATING WHERE CONVECTIVE BOUNDARIES MAY BE
AHEAD OF THE MAIN FRONTAL SYSTEM LATE WEDNESDAY MORNING.
AGAIN...THE GFS HAS A BETTER VISION OF THIS SCENARIO THAN THE NAM
WHICH KEEPS MUCH OF THE STRONG CONVECTION ALONG THE MAIN FRONTAL
BOUNDARY. THUS..EXPECT A CLUSTER OF STRONG/SEVERE STORMS TO BE OVER
SRN LOWER MI INTO NRN IL AND SERN IA BY EARLY AFTERNOON. THE
ENSEMBLE SOLUTIONS FOLLOW THIS CONCEPT WITH THE BETTER PROBABILITIES
FALLING ACROSS SRN LOWER MI INTO NRN IL.
AIR MASS IS FORECAST TO BE MODERATELY UNSTABLE WITH MUCAPE BETWEEN
2000 AND 2500 J/KG FROM CENTRAL IL WSWWD INTO NERN MO AND NERN KS BY
04/18Z. BY THIS TIME...WSWLY LOW LEVEL JET OF 30-45 KT IS EXPECTED
TO EXTEND FROM NRN INDIANA INTO WRN NY STATE COUPLED WITH LOW LEVEL
THERMAL/MOISTURE AXIS. WNWLY MID LEVEL FLOW OF 30-40 KT WILL BE
EXTENDING FROM WI SEWD OVER THE LOWER GREAT LAKES PROVIDING
SUFFICIENT SHEAR PROFILES FOR CONTINUED SUPPORT FOR ISOLATED
SUPERCELLS/MCS STRUCTURES ACROSS THE REGION. STEEP LOW LEVEL LAPSE
RATES IN THE LOWEST 3KM ARE FORECAST TO BE AROUND 7-7.5C/KM WHICH IS
SUFFICIENT FOR LARGE HAIL AND LOCALLY DAMAGING WINDS DURING THE
AFTERNOON AND EVENING ACROSS THE HIGHEST PROBABILITY AREA.
...NY STATE AND PA...
ANALYSIS OF ENSEMBLE DATA SHOWED AN AREA WHERE THERE WILL BE
SUFFICIENT CONDITIONS FOR ISOLATED SUPERCELLS/STRONG THUNDERSTORMS.
THIS AREA IS UNDERNEATH UPPER LEVEL JET EXIT REGION WHERE THERE WILL
ALSO BE FAVORABLE DIVERGENT FLOW TO ENHANCE UVVS. GFS ALSO
INDICATES 30-40 KT OF LOW LEVEL FLOW THRU THIS AREA WITH DEEP LAYER
SHEAR VALUES TO 40 KT AND 0-3KM SR HELICITY OF 450 M2/S2. THIS IS
ILLUSTRATED FAVORABLY IN FORECAST HODOGRAPHS USING THE NAM ALONG
WITH SFC-3KM LAPSE RATES AROUND 7.5C/KM BY LATE AFTERNOON.
IT MAY BE NECESSARY TO CONTINUE TO MONITOR THIS AREA FOR HIGHER
PROBABILITIES FOR HAIL AND ISOLATED TORNADOES. THIS AREA WILL BE
ASSOCIATED WITH AN EWD MOVING N-S WARM FRONT WHERE LOW LEVEL
THERMAL/MOISTURE ADVECTION WILL BE INCREASING DESTABILIZING THE AIR
MASS UNDERNEATH UPPER JET EXIT REGION.
...CENTRAL HIGH PLAINS CO/KS...
ELY SFC FLOW WILL ENHANCE UPSLOPE FLOW/CONVERGENCE ACROSS THIS AREA
DURING THE AFTERNOON AND EVENING. LATEST MODEL SOLUTIONS ARE
CONSISTENT WITH PREVIOUS DAY2 DISCUSSION WITH AN INFLUX OF
MODERATELY UNSTABLE AIR IN THE BOUNDARY LAYER WITH NEARLY DRY
ADIABATIC LAPSE RATES TO SUPPORT DRY MICROBURSTS.
..MCCARTHY.. 07/03/2007
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
|
