SPC AC 251254
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT TUE MAY 25 2010
VALID 251300Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER NORTHERN MAINE...
...THERE IS A SLGT RISK OF SVR TSTMS FROM LAKE SUPERIOR SOUTH ACROSS
THE UPPER MS VALLEY AND SOUTHWESTWARD TO SOUTHEAST CO AND THE
SOUTHERN HIGH PLAINS...
...SYNOPSIS...
A COMPLEX UPPER AIR FLOW REGIME EXISTS ACROSS THE LOWER 48 THIS
MORNING AS AN INTENSE OCCLUDED CYCLONE TRACKS NORTH FROM THE NRN
PLAINS TO THE CANADIAN PRAIRIE PROVINCES...AND AN EXPANSIVE
ANTICYCLONE COVERS THE GREAT LAKES AND NORTHEAST. SOUTH OF THE UPPER
HIGH...A LARGE UPPER LOW WITH A NUMBER OF EMBEDDED SMALLER-SCALE
VORTICES WAS DRIFTING WWD TOWARD THE SOUTHEAST U.S.
COAST. TO THE NORTH...A SHORT WAVE TROUGH AND ASSOCIATED DECAYING
MCS WERE CRESTING THE RIDGE AXIS IN EASTERN CANADA.
DESPITE THE HIGHLY AMPLIFIED PATTERN...MID LEVEL WINDS ARE AOB 40KT
OVER MUCH OF THE CONUS. THE EXCEPTIONS BEING A 80KT SLY JET STREAK
ON THE ERN FLANK OF THE OCCLUDED CYCLONE OVER THE NRN PLAINS...AND A
BELT OF MODEST 40-50KT FLOW WITHIN THE BASE OF THE LARGER SCALE
TROUGH ACROSS THE WEST.
AT THE SURFACE...AN ILL-DEFINED SYNOPTIC FRONTAL ZONE ASSOCIATED
WITH THE OCCLUDED LOW WAS FRAGMENTED BY NUMEROUS CONVECTIVE OUTFLOWS
FROM MN/IA TO KS. A NUMBER OF OTHER CONVECTIVE OUTFLOW BOUNDARIES
EXIST SOUTH OF THE FRONT...OVER OK AND TX. ABUNDANT BOUNDARY LAYER
MOISTURE REMAINS IN PLACE ALONG THE DECAYING FRONTAL ZONE...AND
AMIDST THE VARIOUS OUTFLOWS AND WEAKENING CONVECTIVE SYSTEMS IN OK
AND TX.
...UPPER MS VALLEY...
AS THE OCCLUDED LOW LIFTS INTO CANADA AND INFLUENCE OF THE
ANTICYCLONE TO THE EAST DIMINISHES...THIS AREA MAY UNDERGO WEAK
HEIGHT FALLS. GIVEN THE PROXIMITY OF RESIDUAL FRONTAL ZONE AND
OUTFLOW BOUNDARIES...COUPLED WITH POTENTIAL FOR STRONG
DESTABILIZATION AND WEAK CONVECTIVE INHIBITION...EXPECT
THUNDERSTORMS TO INCREASE. GIVEN GENERALLY WEAK FLOW ALOFT...BULK
SHEAR WILL NOT BE PARTICULARLY SUPPORTIVE OF SUSTAINED OR
WELL-ORGANIZED UPDRAFTS. HOWEVER...MAGNITUDE OF INSTABILITY AND
FOCUSING POTENTIAL OF THE FRONT AND OTHER BOUNDARIES SUGGESTS THAT
MULTICELL ACTIVITY WILL INCREASE ALONG WITH AN INCREASING CHANCE FOR
SOME HAIL AND LOCALLY DAMAGING WIND GUSTS.
...SRN PLAINS TO SERN CO...
THERE IS A LARGE AMOUNT OF UNCERTAINTY ABOUT CONVECTIVE DEVELOPMENT
AND MODE ACROSS THIS AREA TODAY. MOST GUIDANCE HAS NOT DONE WELL
DEPICTING THE CURRENTLY DECAYING AND POORLY ORGANIZED MCS OVER
KS/OK. OUTFLOW AND DEBRIS CLOUDINESS FROM THIS CONVECTION WILL
LIKELY PLAY A ROLE IN NEW STORM DEVELOPMENT IN A VERY UNSTABLE BUT
GENERALLY WEAKLY SHEARED FLOW REGIME.
SOME SYNOPTIC SCALE SUPPORT FOR MORE WIDESPREAD DEVELOPMENT MAY
OCCUR ACROSS THE HIGH PLAINS LATER THIS AFTERNOON WHEN A SUBTLE
SHORT WAVE TROUGH...EVIDENT ON WATER VAPOR IMAGERY ACROSS FOUR
CORNERS AREA ATTM...MOVES NEWD. LIFT WITH THIS FEATURE...COUPLED
WITH MIXING ALONG THE DRY LINE NEAR THE NM/TX BORDER SHOULD BE
ADEQUATE FOR THUNDERSTORM DEVELOPMENT THESE AREAS AND EAST ACROSS
WEST TX AND NORTH INTO PARTS OF KS/CO. ADDITIONAL STORM DEVELOPMENT
APPEARS POSSIBLE AS AIR MASS RECOVERS/DESTABILIZES INVOF RESIDUAL
FRONT IN KS. POCKETS OF STRONGER EFFECTIVE SHEAR WILL MARGINALLY
SUPPORT SUPERCELL STORMS WITH LARGE HAIL AND WIND AND PERHAPS A
TORNADO OR TWO. MOST OF THIS ACTIVITY WILL TEND TO DIE OFF SEVERAL
HOURS AFTER SUNSET.
MOIST POST-FRONTAL UPSLOPE FLOW AND AFOREMENTIONED WEAK SHORT WAVE
MAY BE SUFFICIENT FOR HIGH PLAINS STORMS TO FORM WITHIN WEAK TO
MODEST INSTABILITY ACROSS SERN CO. SHEAR IN THESE AREAS WILL BE A
BIT MORE FAVORABLE FOR STORM ROTATION WITH SOME HAIL/WIND AND
PERHAPS A TORNADO OR TWO.
...MAINE...
SHORT WAVE TROUGH WILL PRODUCE MODEST ASCENT ACROSS NRN MAINE WHERE
ERN EDGE OF STEEP LAPSE RATE PLUME WILL COMBINE WITH MOISTENING AND
HEATING OF THE DAY TO SUSTAIN A FEW STRONG/SEVERE THUNDERSTORMS.
STRENGTHENING NWLY FLOW ALOFT WILL CONTRIBUTE TO SHEAR PROFILES
FAVORABLE FOR UPDRAFT ENHANCEMENT AND FAST-MOVING STORMS WITH BOTH
SEVERE HAIL AND WIND POSSIBLE.
...OZARKS TO LOWER MS VALLEY...
THIS AREA WILL LIE BENEATH BROADLY DIFFLUENT BUT GENERALLY WEAK FLOW
ALOFT. EXPECT AN INCREASE IN PULSE STORMS AGAIN TODAY. AS THIS
ACTIVITY TAPS INTO STRONGER DIURNAL DESTABILIZATION...A FEW
HAIL/WIND EVENTS APPEAR POSSIBLE.
..CARBIN/ROGERS.. 05/25/2010
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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