SPC AC 160556
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT WED JUL 16 2008
VALID 171200Z - 181200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE UPR MS VLY
SWWD INTO THE CNTRL HIGH PLAINS...
...SYNOPSIS...
SRN BRANCH OF THE POLAR WLYS WILL REMAIN ALONG THE CANADIAN BORDER
ON THURSDAY WITH A WEAKER SUB-TROPICAL BRANCH EXISTING FROM THE GRT
BASIN INTO THE CNTRL PLAINS. NUMEROUS MID-LVL SHORTWAVE TROUGHS
WILL TRANSLATE EWD WITHIN BOTH STREAMS AND BE IMPETUS FOR PERIODIC
TSTM CLUSTERS. THESE STORMS WILL FAVOR THE BAROCLINIC ZONE THAT
WILL VACILLATE IN AN E-W CORRIDOR EXTENDING FROM CNTRL/NRN NEW
ENGLAND WWD THROUGH THE CNTRL/UPR GRTLKS...UPR MS VLY...CORN
BELT...CNTRL PLAINS AND FINALLY INTO THE CNTRL/NRN HIGH PLAINS.
...UPR MS VLY SWWD TO THE CNTRL HIGH PLAINS...
A CLUSTER OR TWO OF TSTMS WILL LIKELY BE ONGOING AT 12Z THURSDAY
OVER PARTS OF THE UPR MS VLY AND CNTRL GRTLKS REGION AS A MODEST
MID-LVL WAVE WITHIN THE PRIMARY BELT OF WLYS EJECTS INTO ONTARIO.
AS THIS DISTURBANCE MOVES EWD...PRIMARY BELT OF LOW-MID/LVL FLOW
WILL FOLLOW IN TANDEM.
UPSTREAM...WEAKENING LOW-LEVEL FLOW WILL GRADUALLY BACK AND FOCUS
ACROSS PARTS OF THE CORN BELT AND CNTRL PLAINS DURING THE AFTN. AIR
MASS ALONG/S OF THE FRONT...PROBABLY SITUATED FROM CNTRL WI SWWD
INTO NEB AND NE CO DURING THURSDAY AFTN...WILL BECOME VERY UNSTABLE
GIVEN MID 60S-LWR 70F DEW POINTS BENEATH MODESTLY STEEP H7-H5 LAPSE
RATES.
MODELS HAVE BEEN SUGGESTING FOR QUITE SOMETIME NOW THAT A PIECE OF
THE UPR TROUGH COMPLEX OVER THE SRN GRT BASIN/BAJA CA REGION WILL
ROTATE ABOUT THE RIDGE AND INTO THE CNTRL HIGH PLAINS BY THURSDAY
AFTN. CONVECTION WILL LIKELY INITIATE BOTH OVER THE HIGH PLAINS AND
EWD ALONG THE FRONT INTO NEB AND IA BY MID-AFTN IN ADVANCE OF THIS
DISTURBANCE. VERTICAL SHEAR IS FCST TO BE WEAK...BUT MAY ULTIMATELY
BE STRONGER ALONG SRN PERIPHERY OF THE WAVE...ESPECIALLY OVER THE
PLAINS. THIS IN COMBINATION WITH INCREASING DEEP LAYER
MOISTURE/INSTABILITY WILL LEAD TO ORGANIZED TSTMS WITH LARGE HAIL
AND DMGG WINDS.
EVENING EVOLUTION INTO AN MCS IS LIKELY OVER PARTS OF THE CNTRL
PLAINS AS THE SLY LLJ DIURNALLY INCREASES...MAXIMIZING MOISTURE
TRANSPORT INTO WRN KS AND SRN NEB. OTHER STORMS WILL LIKELY
REGENERATE ALONG THE FRONT RANGE WELL INTO THE EVENING AS OUTFLOW
BOUNDARIES TRAVEL UPSLOPE AMIDST MODEST INSTABILITY. SOME STORMS
WILL CONTINUE TO PRODUCE DMGG WIND GUSTS/HAIL.
...NRN HIGH PLAINS...
BOUNDARY LAYER WILL BE COMPARATIVELY DRIER ACROSS NE WY AND SCNTRL
MT THAN FARTHER S AND E THURSDAY AFTN. BUT...LWR-MID 50S SFC DEW
POINTS COINCIDENT WITH STEEP LAPSE RATES WILL CONTRIBUTE TO 500-1000
J/KG MLCAPE. WEAK UPSLOPE COMPONENT AND THE APPROACH OF THE NEXT
SRN POLAR STREAM DISTURBANCE WILL AID IN ISOLD HIGH-BASED TSTM
INITIATION BY LATE AFTN. EFFECTIVE SHEAR AOA 45 KTS WILL BE
FAVORABLE FOR SUPERCELLS WITH PRIMARILY LARGE HAIL. ACTIVITY WILL
TRY TO DEVELOP EWD ON THE LWR PLAINS TOWARD SW SD OVERNIGHT WITH
PERHAPS ISOLD DMGG WIND GUSTS/HAIL.
...NRN/ERN FL INTO CSTL GA/SC...
SHORT TERM MODELS ARE IN BETTER AGREEMENT ON THE EVENTUAL TRACK OF
THE SFC LOW...THOUGH 00Z NAM IS FARTHER W WITH THE SYSTEM. NUMEROUS
TSTMS WILL DEVELOP OVER NRN/ERN FL AND SPREAD INTO CSTL GA/SC
THROUGH THURSDAY AFTN. ALONG WITH THE HEAVY RAINFALL THREAT...ISOLD
STORMS MAY ALSO PRODUCE DMGG WIND GUSTS. ANY TORNADO THREAT WILL
HINGE ON STRENGTH OF THE LOW-LVL WIND FIELDS...WHICH ARE FCST TO BE
STRONGER IN THE 00Z NAM THAN ANY OTHER MODEL. WITH THIS
UNCERTAINTY...ONLY LOW SVR PROBABILITIES ARE JUSTIFIED ATTM.
..RACY.. 07/16/2008
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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