SPC AC 060535
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1235 AM CDT MON JUL 06 2009
VALID 061200Z - 071200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN ROCKIES/NRN HIGH
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CNTRL/SRN HIGH
PLAINS...
...SYNOPSIS...
UPR FLOW PATTERN BECOMES SLIGHTLY MORE AMPLIFIED ON MONDAY.
STUBBORN UPR LOW WILL REMAIN OVER ONT/QUE THROUGH THE PD AS MID-LVL
JET STREAKS DIG SEWD INTO THE UPR OH VLY/LWR GRT LKS REGION. THIS
WILL MAINTAIN A BROAD LONGER WAVE TROUGH OVER THE ERN HALF OF THE
COUNTRY. UPSTREAM...UPR RIDGE OVER THE GREAT BASIN WILL BUILD NWD
TOWARD THE NRN PLNS AS THE ERN PAC UPR TROUGH MOVES ENEWD ACROSS THE
NRN INTERMOUNTAIN W AND NRN ROCKIES.
...NRN ROCKIES/NRN HIGH PLNS...
A FEW TSTMS ARE EXPECTED TO BE ONGOING AT 12Z MONDAY ACROSS THE NRN
INTERMOUNTAIN W...DOWNSTREAM FROM A LEAD SHORTWAVE TROUGH EJECTING
TOWARD SRN BC/AB. ACTIVITY WILL MOVE ACROSS THE INTERNATIONAL
BORDER MONDAY MORNING. PWAT VALUES WILL INCREASE OVER THE REGION BY
AFTN...BOTH BY CONTRIBUTIONS FROM RECYCLED MOISTURE AND ADVECTION OF
50S DEW POINTS FROM THE HIGH MT/WY PLAINS. BY AFTN...STRONG HEATING
AND STEEP MID-TROPOSPHERIC LAPSE RATES WILL BOOST MLCAPES TO AROUND
1500 J/KG AS FAR W AS THE DIVIDE.
COMBINATION OF INCREASED LARGE SCALE ASCENT...MAGNITUDE OF MOISTURE
AND ENHANCED LLVL CONVERGENCE INVOF MOUNTAINS/SFC LEE LOW WILL LEAD
TO SCTD TSTMS OVER ERN ID/WRN MT BY MID-AFTN. FCST HODOGRAPHS SHOW
A BACKING MID-LVL FLOW REGIME AOA 45 KTS THROUGH THE AFTN ACROSS THE
INITIATION ZONE. THIS WILL RESULT IN MARGINAL VERTICAL SHEAR...BUT
FAIRLY STRONG AND DEEP SWLYS. WHILE A SUPERCELL OR TWO CANNOT BE
RULED OUT DURING STORM INFANCY /ISOLD TORNADOES PSBL/...ALL
INDICATIONS ARE THAT UPSCALE DEVELOPMENT INTO SMALL SCALE LEWPS/BOWS
WILL EVENTUALLY RESULT WITH SVR WIND GUSTS/HAIL SPREADING ACROSS
CNTRL MT DURING THE EVENING. ACTIVITY MAY BACKBUILD AND/OR DEVELOP
SWD INTO PARTS OF NRN WY AS WELL. THE SVR THREAT MAY CONTINUE INTO
MONDAY NIGHT OVER ERN MT...THOUGH ACTIVITY WILL LIKELY ACCELERATE
AWAY FROM THE STRONGER FORCING.
...NRN/CNTRL HIGH PLNS...
MODEST WNWLY FLOW ALOFT/SUBSIDENCE IN WAKE OF A WEAK UPR LVL WAVE
TRANSLATING E OF THE REGION EARLY MONDAY WILL ADVECT SOMEWHAT DRIER
AIR MASS EWD INTO THE CNTRL ROCKIES. THUS...FOCUS FOR TSTMS WILL BE
FARTHER E THAN PREVIOUS DAYS...LIKELY INITIATING ALONG THE LEE
TROUGH OVER THE HIGH PLNS. LLVL MOISTURE /SFC DEW POINTS IN THE 50S/
ARE FCST TO BE MAINTAINED ALONG/E OF THIS FEATURE...CONTRIBUTING TO
MLCAPES TO 1500-2500 J/KG.
NEXT WEAK UPR JET STREAK...NOW OVER THE NRN GREAT BASIN...WILL REACH
THE TROUGH BY AFTN AND RESULT IN NUMEROUS TSTMS FROM ERN CO SWD INTO
CNTRL NM. ROUGHLY 40 KTS OF WNW H5 FLOW ATOP WEAK SELY LLVL WINDS
WILL BOOST VERTICAL SHEAR SUFFICIENT FOR ISOLD SUPERCELLS WITH LARGE
HAIL. ACTIVITY WILL CONGEAL INTO TSTM CLUSTERS DURING THE EVENING
AND MIGRATE SEWD INTO WRN KS...TX-OK PNHDLS AND ERN NM WITH THREATS
FOR HIGH WINDS/HAIL.
...NRN NY AND CNTRL/NRN NEW ENGLAND...
MID-LVL WAVE ROUNDING BASE OF THE SERN CANADA UPR LOW WILL EJECT
NEWD ACROSS THE REGION DURING PEAK HEATING. SYSTEM IS ALREADY
SUPPORTING NOCTURNAL TSTMS MOVING INTO WRN NY. DOWNSTREAM...SFC DEW
POINTS IN THE LWR-MID 50S BENEATH RELATIVELY COLD MID-LVL
TEMPERATURES COMBINED WITH FAVORABLE LARGE SCALE ASCENT WILL LEAD TO
DEVELOPMENT/MAINTENENCE OF TSTMS DOWNSTREAM ACROSS NRN/ERN NY AND
NRN/CNTRL NEW ENGLAND. MODEST WLY FLOW THROUGH A DEEP LAYER WILL BE
FAVORABLE FOR A FEW STG/ISOLD SVR STORMS CAPABLE OF LARGE HAIL/GUSTY
WINDS.
...SERN STATES TO E TX...
COMPLEX ARRAY OF OUTFLOW BOUNDARIES WILL EXIST ACROSS THE REGION ON
MONDAY. HEATING AMIDST A WEAK CAP AND WEAK CYCLONIC FLOW ALOFT WILL
CONTRIBUTE TO TSTM DEVELOPMENT INVOF THESE BOUNDARIES ON MONDAY.
LAPSE RATES WILL BE RATHER WEAK AND RELATIVELY WEAK FLOW ALOFT WILL
MITIGATE WIDESPREAD SVR WEATHER. HOWEVER...VERY MOIST BOUNDARY
LAYER AND POTENTIAL FOR STORM MERGERS WILL AT LEAST BE FAVORABLE FOR
ISOLD WET MICROBURSTS.
..RACY/HURLBUT.. 07/06/2009
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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