SPC AC 110551
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT SAT JUL 11 2009
VALID 121200Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE TN VLY NWWD TO THE
CNTRL HIGH PLAINS...
...SYNOPSIS...
UPR FLOW REGIME WILL ESSENTIALLY REMAIN THE SAME THROUGH THE WEEKEND
WITH THE MOST PROMINENT FEATURE CONTINUING TO BE THE SPRAWLING HOT
HIGH PRESSURE OVER THE SCNTRL/SWRN PARTS OF THE NATION. THE UPR
TROUGH OVER SERN CANADA WILL REMAIN IN PLACE WITH SEVERAL
DISTURBANCES ROTATING SEWD THROUGH THE UPR GRTLKS AND NERN STATES.
TO THE W...ANOTHER UPR SYSTEM WILL EJECT NEWD THROUGH THE PAC NW AND
NRN ROCKIES THROUGH THE PD. A SEPARATE BELT OF MODEST WNWLY MID-LVL
FLOW WILL EXIST ALONG THE NRN PERIPHERY OF THE RIDGE AXIS...LIKELY
CARRYING SVRL LOW-AMPLITUDE PERTURBATIONS E THEN SEWD FROM THE CNTRL
ROCKIES TO THE SERN STATES.
IN THE LWR LVLS...A CDFNT WILL CONTINUE TO SLOW SWD MOVEMENT ACROSS
THE CAROLINAS AND TN VLY IN WAKE OF THE NERN TROUGH. TAIL-END OF
THIS FRONT WILL THEN REMAIN QSTNRY FROM THE LWR OH VLY NWWD INTO THE
CNTRL HIGH PLNS.
...TN VLY NWWD TO THE CNTRL HIGH PLNS...
LOW CONFIDENCE FCST WILL CONTINUE ON SUNDAY WITH POTENTIAL FOR SVRL
TSTM CLUSTERS TO RIDE ALONG NRN PARTS OF THE RIDGE FROM THE CNTRL
HIGH PLAINS TO THE TN VLY THIS WEEKEND. TIMING...SEVERITY AND
PLACEMENT OF EACH MCS WILL BE HIGHLY UNCERTAIN AND ARGUES FOR A
FAIRLY EXTENSIVE ZONE OF LOW-END SLGT PROBABILITIES.
MODELS ARE SOMEWHAT CONSISTENT IN MAINTAINING CHARACTER OF A MID-LVL
WAVE...POSSIBLY CONVECTIVELY ENHANCED...ACROSS THE CNTRL PLNS
SATURDAY...REACHING THE MID-MS VLY BY 12Z SUNDAY. ASSOCD LLVL WARM
ADVECTION ALONG/N OF THE AFOREMENTIONED FRONTAL ZONE WILL PROBABLY
BE IMPETUS FOR AN EARLY MORNING MCS ACROSS THE MID-MS VLY EARLY
SUNDAY. DOWNSTREAM AIR MASS IS APT TO BE CONTAMINATED BY DEBRIS
CLOUDS THROUGH THE DAY...LIMITING DESTABILIZATION...ESPECIALLY IN
LIGHT OF RELATIVELY WARM TROPOSPHERIC TEMPERATURES.
HOWEVER...POCKETS OF HEATING AND POTENTIAL FOR ENHANCED MID-LVL FLOW
ALONG THE BASE OF THE MCV MAY BOOST POTENTIAL FOR A COUPLE ORGANIZED
STORMS WITH DMGG WINDS ACROSS THE TN VLY...AND MAYBE AS FAR E AS
PARTS OF THE CAROLINAS.
OTHERWISE...WHILE TSTM INITIATION CANNOT BE COMPLETELY RULED OUT
ALONG THE FRONT ACROSS PARTS OF CNTRL/NRN MO AND SRN IA DURING PEAK
HEATING...IT APPEARS PRIMARY SVR THREATS WILL PROBABLY EVOLVE
FARTHER UPSTREAM IN NEB...SRN SD AND THE WY HIGH PLAINS. MOST
MODELS SEEM TO SUGGEST THAT A MODEST PV-ANOMALY WILL ROTATE FROM THE
GRT BASIN/DESERT SW INTO THE CNTRL PLNS BY SUNDAY EVENING. RIBBON
OF LWR 70S BOUNDARY LAYER DEW POINTS BENEATH RESIDENT STEEP MID-LVL
LAPSE RATES WILL CONTRIBUTE TO VERY UNSTABLE CONDITIONS. STRONG
MLCINH WILL LOCALLY ERODE AS STRONG HEATING COUPLES WITH MODEST
ASCENT AND INCREASING/SUSTAINED LLVL CONVERGENCE/UPSLOPE. TSTM
INITIATION APPEARS MOST LIKELY OVER BOTH THE HIGH PLNS AND INVOF THE
FRONT. ANY STORM WILL HAVE THE AVAILABILITY TO BULK SHEAR OF 40-45
KTS AND GIVEN MAGNITUDE OF INSTABILITY...SUPERCELLS WILL BE POSSIBLE
WITH LARGE HAIL...DMGG WINDS AND POSSIBLY A COUPLE OF TORNADOES.
ACTIVITY MAY CONGEAL INTO ONE OR MORE MCS/S AND MOVE DOWNSTREAM INTO
PARTS OF THE LWR MO VLY/MID-MS VLY BY 12Z MONDAY WITH CONTINUED
POTENTIAL FOR HIGH WINDS/HAIL.
...NRN INTERMOUNTAIN W...
FAIRLY ROBUST LARGE SCALE ASCENT ALONG/N OF A 50-70 KT MID-LVL JET
WILL SUPPORT SCTD TSTMS SUNDAY AFTN/NIGHT ACROSS ERN WA/ORE INTO
NRN/CNTRL ID AND SWRN MT. DEEP LAYER SHEAR AND PWATS WILL INCREASE
THROUGH THE DAY...LIKELY SUPPORTING THE RISK FOR STG-ISOLD SVR
STORMS. ONCE MAGNITUDE OF MOISTURE IS BETTER KNOWN...LATER OUTLOOKS
MAY NEED AN UPGRADE TO A SLGT RISK.
..RACY.. 07/11/2009
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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