SPC AC 042020
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
0320 PM CDT FRI JUL 04 2008
VALID 051200Z - 061200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN
PLAINS...
CORRECTED FOR TYPO
...NRN PLAINS...
AN UPPER-LEVEL RIDGE WILL MOVE EWD TONIGHT DAMPENING AND REACHING
THE UPPER MIDWEST SATURDAY AS A FAST-MOVING UPPER-LEVEL TROUGH TAKES
SHAPE OVER SRN CANADA. THE SRN EDGE OF THIS FEATURE WILL MOVE ACROSS
THE NRN PLAINS PROVIDING LARGE-SCALE ASCENT FOR SCATTERED
THUNDERSTORM DEVELOPMENT SATURDAY AFTERNOON. AT THE SFC...A COLD
FRONT WILL MOVE QUICKLY EWD INTO THE NRN PLAINS WITH THUNDERSTORMS
DEVELOPING ALONG BOUNDARY. AHEAD OF THE FRONT...MODERATE INSTABILITY
IS FORECAST WHICH SHOULD SUSTAIN THE ACTIVITY INTO THE EVENING
ACROSS ERN ND...NWRN MN AND ECNTRL SD.
AT MID-LEVELS...THE ENTRANCE REGION OF A 50 TO 65 KT JET MAX WILL
OVERSPREAD THE REGION SATURDAY CREATING MODERATE VERTICAL SHEAR
PROFILES. FORECAST SOUNDINGS ALONG THE BOUNDARY SHOW 0-6 KM SHEAR
VALUES IN THE 40 TO 50 KT RANGE SUGGESTING SUPERCELLS WILL BE
POSSIBLE. HOWEVER...LINEAR FORCING ALONG THE BOUNDARY AND VEERED SFC
WINDS SHOULD ALSO RESULT IN LINE SEGMENTS. ALTHOUGH MID-LEVEL TEMPS
WILL BE QUITE WARM...LARGE HAIL MAY OCCUR DUE TO THE AMOUNT OF
INSTABILITY AND STEEP LAPSE RATES EVIDENT ON FORECAST SOUNDINGS. IN
ADDITION...WIND DAMAGE WILL ALSO BE POSSIBLE ESPECIALLY WITH BOWING
MULTICELL LINE SEGMENTS.
...NRN AND CNTRL HIGH PLAINS...
WEST TO SOUTHWEST FLOW WILL BE IN PLACE SATURDAY ACROSS THE REGION
AS AN UPPER-LEVEL TROUGH MOVES EWD ACROSS SRN CANADA. AT THE
SFC...WINDS IN THE NRN HIGH PLAINS WILL BE NLY IN THE WAKE OF A COLD
FRONT WITH MODELS FORECASTING AN AXIS OF INSTABILITY LOCATED BEHIND
THE FRONT FROM CNTRL NEB EXTENDING NWWD INTO NERN WY. THUNDERSTORMS
SHOULD DEVELOP ALONG THE INSTABILITY AXIS AND SWD ALONG THE FRONT IN
ERN CO. FORECAST SOUNDINGS ACROSS THE REGION SATURDAY AFTERNOON SHOW
ENOUGH VERTICAL SHEAR ACROSS ERN WY...WRN NEB AND SWRN SD FOR
MARGINALLY SEVERE MULTICELL STORMS. AN ISOLATED SUPERCELL MAY ALSO
OCCUR WHERE INSTABILITY IS MAXIMIZED. STEEP LAPSE RATES ON FORECAST
SOUNDINGS SUGGEST HAIL WILL BE POSSIBLE WITH THE STRONGER CORES.
ISOLATED STRONG WIND GUSTS MAY ALSO OCCUR WITH THE MORE PERSISTENT
STORMS ESPECIALLY SATURDAY EVENING WHEN FLOW IS FORECAST TO
STRENGTHEN SOMEWHAT ACROSS THE REGION.
...MID-MO VALLEY...
AN UPPER-LEVEL RIDGE OVER THE SRN ROCKIES WILL GRADUALLY SHIFT EWD
INTO THE CNTRL HIGH PLAINS SATURDAY. NLY FLOW IS FORECAST ACROSS THE
MID-MO VALLEY WITH AN AXIS OF INSTABILITY LOCATED FROM CNTRL NEB
SSEWD INTO THE OZARK REGION. ISOLATED TO SCATTERED THUNDERSTORMS
SHOULD INITIATE ALONG THE INSTABILITY AXIS SATURDAY AFTERNOON.
ALTHOUGH MID-LEVEL FLOW IS RELATIVELY WEAK...SUBSTANTIAL DIRECTIONAL
SHEAR IS EVIDENT ON FORECAST SOUNDINGS WHICH MAY BE SUFFICIENT FOR A
MARGINAL SEVERE THREAT. A FEW OF THE STORMS COULD CONTAIN ISOLATED
STRONG WIND GUSTS.
...CNTRL APPALACHIANS/ERN SEABOARD...
A WEAK UPPER-LEVEL TROUGH IS FORECAST ACROSS THE OH VALLEY SATURDAY.
THUNDERSTORMS SHOULD DEVELOP ALONG AN AXIS OF INSTABILITY ACROSS THE
CNTRL APPALACHIANS AND ERN SEABOARD WHERE LIFT SHOULD BE SLIGHTLY
ENHANCED AHEAD OF THE UPPER-LEVEL TROUGH. FORECAST SOUNDINGS SHOW
ENOUGH INSTABILITY COMBINED WITH ABOUT 25 KT OF VERTICAL SHEAR FOR A
MARGINAL SEVERE THREAT SATURDAY AFTERNOON. HAIL MAY OCCUR WITH THE
MORE INTENSE CELLS AND STRONG WIND GUSTS WILL ALSO POSSIBLE
ESPECIALLY WHEN LOW-LEVEL LAPSE RATES SHOULD BE STEEPEST IN THE LATE
AFTERNOON.
..BROYLES.. 07/04/2008
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
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