SPC AC 032006
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0306 PM CDT FRI AUG 03 2007
VALID 032000Z - 041200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NEW ENGLAND AND
THE NRN APPALACHIAN MTNS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN AND
CNTRL PLAINS...
...NEW ENGLAND/NRN APPALACHIAN MTNS...
AN UPPER-LEVEL TROUGH WAS EVIDENT ON WATER VAPOR IMAGERY OVER ERN
ONTARIO WITH THE SRN EXTENT OF THE TROUGH LOCATED IN THE NRN
APPALACHIAN MTNS. THIS FEATURE ALONG WITH LOW-LEVEL CONVERGENCE FROM
A PRE-FRONTAL TROUGH IS PROVIDING LIFT SUFFICIENT FOR NUMEROUS
THUNDERSTORMS FROM MAINE SWWD ACROSS CNTRL NY INTO WRN PA. SFC
DEWPOINTS AHEAD OF THE PRE-FRONTAL TROUGH ARE IN THE MID 60S F AND
MODERATE TO STRONG INSTABILITY EXISTS ACROSS MOST OF THE NERN STATES
ACCORDING TO OBJECTIVE ANALYSIS. THIS SHOULD SUSTAIN WIDESPREAD
STORM DEVELOPMENT THROUGH THE EARLY EVENING WITH A NEARLY CONTINUOUS
LINE ORGANIZING AND MOVING EWD ACROSS THE REGION.
THE LATEST 88D VWPS ACROSS THE REGION SHOW THE STRONGEST VERTICAL
SHEAR PROFILES ACROSS MAINE WITH 0-6 KM SHEAR VALUES IN THE 30 TO 40
KT RANGE. DUE TO THE MAGNITUDE OF VERTICAL SHEAR...SUPERCELLS WILL
POSSIBLE IN MAINE WITH SEVERE MULTICELLS ALSO LIKELY. FURTHER
SOUTHWEST FROM VT AND NH SWWD ACROSS CNTRL NY INTO PA...VERTICAL
SHEAR IS CONSIDERABLY WEAKER WHICH SHOULD BE SUFFICIENT FOR A
MULTICELL THREAT. STEEP LOW-LEVEL LAPSE RATES AND UNIDIRECTIONAL
LOW-LEVEL FLOW MAY ALSO ENHANCE THE WIND DAMAGE THREAT WITH
SUPERCELLS AND THE BETTER ORGANIZED LINE SEGMENTS. IN
ADDITION...FORECAST SOUNDINGS SHOW STEEP MID-LEVEL LAPSE RATES WITH
RELATIVELY COLD TEMPS ALOFT ASSOCIATED WITH THE UPPER TROUGH WHICH
SHOULD SUPPORT A LARGE HAIL THREAT WITH THE STRONGER CELLS LATE THIS
AFTERNOON INTO EARLY EVENING.
...NRN AND CNTRL PLAINS...
THE LATEST WATER VAPOR IMAGERY SHOWS A WELL-DEFINED LOW-AMPLITUDE
UPPER-LEVEL TROUGH CURRENTLY OVER WY. LARGE-SCALE ASCENT AHEAD OF
THIS FEATURE WILL SUPPORT SCATTERED THUNDERSTORMS DEVELOPING ACROSS
THE REGION ATTM. STORM COVERAGE SHOULD GRADUALLY INCREASE THROUGH
EARLY EVENING WITH AN MCS ORGANIZING AND MOVING ESEWD ACROSS SD AND
NRN NEB THIS EVENING INTO THE OVERNIGHT PERIOD.
REGIONAL PROFILERS AND WSR-88D VWPS ACROSS THE REGION CURRENTLY SHOW
GRADUALLY VEERING WINDS FROM THE SFC TO 3 KM WITH WINDS OF 30 TO 40
KT AT AND JUST ABOVE 500 MB. THIS IS CREATING MODERATE VERTICAL
SHEAR FROM NERN WY EXTENDING SEWD ACROSS MOST OF SD AND NEB.
ATTM...THE STRONGER INSTABILITY IS LOCATED IN WRN NEB AND FAR ERN WY
WHERE MLCAPE VALUES ARE IN THE 1500 TO 2000 J/KG RANGE. AS STORMS
INCREASE IN COVERAGE ALONG THE INSTABILITY AXIS...THE SHEAR APPEARS
SUFFICIENT FOR SUPERCELLS. LOW-LEVEL SHEAR ON THE NORTH PLATTE NEB
PROFILER APPEARS STRONG ENOUGH FOR AN ISOLATED TORNADO THREAT AS
WELL. ALTHOUGH MID-LEVEL TEMPS ARE QUITE WARM...SUPERCELLS STILL
SHOULD BE CAPABLE OF PRODUCING ISOLATED LARGE HAIL. WIND DAMAGE WILL
ALSO BE POSSIBLE WITH THE GREATEST POTENTIAL EXISTING EARLY THIS
EVENING AS THE LOW-LEVEL JET STRENGTHENS. THE WIND DAMAGE THREAT MAY
CONTINUE THROUGH LATE EVENING AS AN MCS MOVES ESEWD REACHING ERN SD
AND POSSIBLY NERN NEB AFTER MIDNIGHT.
FURTHER NORTHEAST ACROSS NERN ND...A CLUSTER OF STRONG THUNDERSTORMS
IS ONGOING ON THE NOSE OF THE LOW-LEVEL JET. OBJECTIVE ANALYSIS
CURRENTLY SHOWS THE STORMS ALONG THE NERN EDGE OF A POCKET OF
MODERATE INSTABILITY. IN ADDITION...THE LATEST WSR-88D VWP NEAR
GRAND FORKS ND HAS ABOUT 40 KT OF FLOW AT 6 TO 8 KM. THIS COMBINED
WITH 500 MB TEMPS AROUND -10C SUGGESTS A MARGINAL HAIL THREAT MAY
CONTINUE THROUGH LATE AFTERNOON WITH THIS CONVECTIVE CLUSTER.
..BROYLES.. 08/03/2007
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