SPC AC 290547
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1247 AM CDT THU JUN 29 2006
VALID 291200Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NORTHEAST
AND MID ATLANTIC...
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE MID MS
VALLEY...
...SYNOPSIS...
STRONG UPPER TROUGH WILL PROGRESS EAST FROM THE GREAT LAKES TO THE
MID ATLANTIC AND NEW ENGLAND TODAY WHILE UPPER RIDGE REMAINS
ANCHORED ACROSS THE FAR WEST AND FOUR CORNERS AREAS. A WEAK
SHORTWAVE IMPULSE WILL TRAVEL AROUND THE NWRN/NRN PERIPHERY OF THE
WRN RIDGE...POSSIBLY PHASING WITH A LOW AMPLITUDE SHORT WAVE
EMBEDDED WITHIN FASTER WLY FLOW SPREADING ACROSS THE PACIFIC
NORTHWEST AND SWRN CANADA. WEAK TO MODEST NWLY MID LEVEL FLOW WILL
RESIDE ATOP A RESIDUAL FRONTAL ZONE SITUATED FROM THE CNTRL/SRN
APPALACHIANS NWWD INTO THE MID MS VALLEY. HIGH PRESSURE...SURFACE
AND ALOFT...WILL ENCOMPASS MUCH OF THE SOUTH/LOWER MS VALLEY AND SRN
PLAINS.
...NORTHEAST TO MID ATLANTIC...
DYNAMIC FORCING FOR ASCENT ASSOCIATED WITH APPROACHING UPPER TROUGH
WILL ACT ON GRADUALLY DESTABILIZING AIR MASS TO RESULT IN
POTENTIALLY WIDESPREAD DEEP CONVECTION ACROSS MUCH OF THE EAST
TODAY. IN ADDITION TO AGGRAVATING THE FLOODING SITUATION IN SOME
AREAS...RELATIVELY HIGH BOUNDARY LAYER MOISTURE AND POCKETS OF
STRONGER SURFACE HEATING AHEAD OF THE UPPER TROUGH AND ASSOCIATED
FRONT WILL CONTRIBUTE TO SUFFICIENT INSTABILITY FOR SCATTERED SEVERE
STORMS. DEEP LAYER SLY FLOW AND MODEST VERTICAL SHEAR SHOULD RESULT
IN LINE SEGMENTS AND PERHAPS A FEW SUPERCELLS WITH BOTH HAIL AND
WIND POTENTIAL. A MORE CONCENTRATED SEVERE WEATHER THREAT MAY EVOLVE
WHERE SURFACE CONVERGENCE IS MAXIMIZED NEAR WEAK FRONTAL WAVE
POSSIBLY DEVELOPING ON THE FRONT IN RESPONSE TO STRONGER
FORCING/ASCENT ASSOCIATED WITH A SHORT WAVE IMPULSE SPREADING ACROSS
THE MID ATLANTIC REGION WITHIN THE LARGER SCALE TROUGH. IF STRONG
INSTABILITY CAN DEVELOP AHEAD OF THIS IMPULSE AND SURFACE
LOW...HIGHER SEVERE PROBABILITIES...INDICATING ENHANCED SEVERE
WEATHER POTENTIAL...MAY NEED TO BE ADDED IN THE METRO CORRIDOR FROM
DCA TO JFK IN LATER OUTLOOKS.
...MID MS VALLEY/MIDWEST...
ONGOING SMALL MCS OVER ERN MO/WRN IL...AND FRONTAL CONVECTION OVER
THE OH VALLEY...WILL ACT TO REINFORCE RESIDUAL BAROCLINIC BOUNDARY
SITUATED OVER THESE AREAS. INSTABILITY IS LIKELY TO INCREASE NEAR
THIS BOUNDARY WITH STRONG DAYTIME HEATING. DESPITE RELATIVELY WEAK
FORCING FOR ASCENT...PERSISTENT LOW LEVEL CONVERGENCE AND HEATING
MAY PROVE ADEQUATE TO OVERCOME WEAK CAP ACROSS THE AREA FOR ISOLATED
TSTM DEVELOPMENT DURING THE AFTERNOON. GREATER DEVELOPMENT POTENTIAL
APPEARS MAY OCCUR AFTER DARK ACROSS THE REGION AS NOCTURNAL LOW
LEVEL JET ENHANCES LIFT ACROSS THE FRONT COINCIDENT WITH APPROACH
AND PASSAGE OF LOW AMPLITUDE MID LEVEL SHORT WAVE TROUGH. LATEST
GUIDANCE STRONGLY SUGGESTS A CLUSTER OF STORMS WITH HAIL AND
POSSIBLE STRONG WINDS COULD EVOLVE LATER THURSDAY NIGHT FROM SERN
IA/ERN MO SEWD INTO THE LOWER OH VALLEY.
...NRN ROCKIES TO NRN HIGH PLAINS...
WEAK MID LEVEL IMPULSE CURRENTLY MOVING NWD ACROSS NRN CA IS
FORECAST TO TURN EAST AND ACCELERATE ACROSS SRN ID AND MT THROUGH
THURSDAY NIGHT. MARGINALLY UNSTABLE AND DEEPLY MIXED AIR MASS WILL
PRECEED THIS FEATURE AND CONTRIBUTE TO INCREASING COVERAGE OF
HIGH-BASED TSTMS THROUGH THE AFTERNOON. A FEW STORMS COULD PRODUCE
STRONG/DAMAGING OUTFLOW GUSTS...IN ADDITION TO MARGINALLY SEVERE
HAIL. A WEAK FRONT IS FORECAST TO DROP SOUTH ACROSS CNTRL/ERN MT
DURING THE LATE EVENING ASSOCIATED WITH SHORT WAVE CROSSING SWRN
CANADA. MOIST POST-FRONTAL UPSLOPE FLOW MAY ACT TO SUSTAIN A SMALL
FORWARD-PROPAGATING MCS...EVOLVING FROM EARLIER EVENING
ACTIVITY...AND DEVELOPING EAST ACROSS SERN MT THROUGH EARLY FRIDAY.
...SOUTHWEST...
STRONG LOCALIZED DESTABILIZATION WILL OCCUR BENEATH UPPER RIDGE AXIS
AND LEAD TO NUMEROUS AFTERNOON AND EVENING TSTMS ACROSS THE
SOUTHWEST AND INTERMOUNTAIN WEST. ELY MID LEVEL FLOW INCREASING ON
THE SRN PERIPHERY OF THE UPPER RIDGE AXIS...AND WEAK SUB-TROPICAL
DISTURBANCES TRACKING NWWD FROM MEXICO...MAY ACT TO ENHANCE
CONVECTIVE ORGANIZATION AND RESULT IN A FEW SEVERE HAIL/WIND EVENTS.
..CARBIN/JEWELL.. 06/29/2006
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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