DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 281945
SWODY1
SPC AC 281943

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0243 PM CDT THU JUN 28 2012

VALID 282000Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM FAR SERN MI INTO NRN OH
AND WRN PA...

ONLY MINOR TWEAKS WERE MADE TO THE OUTLOOK...AND THE PREVIOUS
THINKING REMAINS VALID.

...LOWER MI INTO NRN OH AND WRN PA...
DESPITE EXTREME HEAT ACROSS THE REGION...MODIFIED SOUNDINGS INDICATE
SUBSTANTIAL CAPPING REMAINS. HOWEVER...AS A WEAK TROUGH CONTINUES
SEWD ACROSS THE GREAT LAKES...SOME COOLING AND MOISTENING WILL OCCUR
ALONG THE SURFACE FRONT. CONFLUENT 850 MB FLOW AS WELL AS A
SUBSTANTIAL THETA-E AXIS AND WARM ADVECTION MAY YET RESULT IN EARLY
EVENING DEVELOPMENT. WITH HIGH PWAT...STEEP LAPSE RATES AND WNWLY
FLOW ALOFT...DAMAGING WINDS WOULD BE LIKELY IF STORMS FORM AND MERGE
INTO AN MCS. HAIL WOULD ALSO BE LIKELY WITH THE STRONGEST CORES.

..JEWELL.. 06/28/2012

.PREV DISCUSSION... /ISSUED 1253 PM CDT THU JUN 28 2012/

CORRECTED SLGT RISK AREA DESCRIPTION.

...SYNOPSIS...
SEE NO REASON TO DEVIATE SUBSTANTIALLY FROM EARLIER FORECAST
REASONING WITH THIS UPDATE. EXPANSIVE SUMMERTIME ANTICYCLONE AND
VERY WARM TEMPS THROUGH A DEEP LAYER OF THE ATMOSPHERE ENCOMPASS
MUCH OF THE CNTRL/SRN U.S. WEAK HEIGHT FALLS ASSOCIATED WITH A SHORT
WAVE TROUGH NEARING HUDSON BAY WILL ACT TO SUPPRESS THE UPPER RIDGE
FROM THE GREAT LAKES TO WRN MID ATLANTIC THROUGH EARLY FRI. SURFACE
FRONT ASSOCIATED WITH THE IMPULSE IN CANADA WILL CONTINUE TO WEAKEN
AND STALL FROM THE CNTRL HIGH PLAINS TO MIDWEST AMIDST HOT AND
STRONGLY CAPPED AIRMASS. A CORRIDOR OF MODEST ASCENT/WARM ADVECTION
DEVELOPS ALONG AND AHEAD OF THE FRONT...FROM LOWER MI ACROSS THE ERN
GREAT LAKES THROUGH THIS EVENING AND WILL SPREAD ACROSS THE
NORTHEAST AND MID ATLANTIC OVERNIGHT.

ON THE WRN FLANK OF THE ANTICYCLONE A NARROW PLUME OF HIGHER PW AIR
EXTENDS FROM THE SWRN DESERTS ACROSS THE ROCKIES WITHIN AN AXIS OF
RELATIVELY WEAK MID LEVEL FLOW. A SHORT WAVE TROUGH EMBEDDED WITHIN
SOMEWHAT STRONGER SWLY FLOW ACROSS THE NORTHWEST WILL TRACK NEWD
ACROSS ID AND WRN MT THROUGH THIS EVENING.

...LOWER GREAT LAKES TO NORTHEAST...
PERSISTENT LIFT AND MOISTENING ALONG THE EDGE OF THE PRONOUNCED EML
PLUME SITUATED WITHIN THE DAMPENING UPPER RIDGE AXIS MAY BE
SUFFICIENT FOR SCATTERED TSTM DEVELOPMENT LATE TODAY THROUGH TONIGHT
FROM LOWER MI ACROSS NRN OH AND INTO WRN NY/PA. AIRMASS TRAJECTORIES
ORIGINATING IN VERY HOT UNSTABLE REGIME TO THE WEST AND MODEST
EFFECTIVE SHEAR ON THE ORDER OF 30-40KT WILL AID CONVECTIVE VIGOR
WITH SOME POSSIBILITY FOR A SMALL MCS EVOLVING AND SPREADING ESEWD.
SCATTERED SEVERE HAIL AND PERHAPS A COUPLE WIND EVENTS CANNOT BE
RULED OUT.

...MIDWEST...
FARTHER WEST ALONG THE WEAK FRONT/WIND SHIFT...FROM SW LOWER MI AND
NRN IND TO IL/IA...STORM COVERAGE IS MUCH MORE UNCERTAIN GIVEN
STRONG CONVECTIVE INHIBITION AND WEAKER FORCING. HOWEVER...VERY
UNSTABLE TO EXTREMELY UNSTABLE CONDITIONS ARE LIKELY WITHIN THIS
CORRIDOR AS TEMPERATURES CLIMB TO AOA 100F. SOME MODEL SCENARIOS
DEPICT POSSIBLE STORM INITIATION NEAR LAKE BREEZE/FRONT
INTERSECTION...FROM NRN IL ACROSS IND...DURING THE LATE AFTERNOON.
HOWEVER...LATEST HRRR BACKS OFF EARLIER INDICATIONS OF STORMS
INITIATING ACROSS ERN IA. IF ANY STORMS CAN INITIATE...THE PROSPECT
FOR SEVERE HAIL AND HIGH WINDS WILL EXIST GIVEN EXPECTED MAGNITUDE
OF INSTABILITY AND SHEAR. THE CONDITIONAL NATURE OF THIS THREAT IN
SUCH A STRONGLY CAPPED REGIME SUGGESTS MAINTAINING LOW SEVERE
PROBABILITIES AT THIS TIME.

...ROCKIES TO CNTRL PLAINS...
SCATTERED TSTMS APPEAR LIKELY WITHIN THE NARROW MOIST AXIS
OVERSPREADING THE HIGHER TERRAIN FROM ERN AZ TO CO THIS AFTERNOON. A
FEW OF THESE STORMS WILL LIKELY PRODUCE GUSTY WINDS GIVEN STEEP
LAPSE RATE REGIME BUT LACK OF STRONGER FLOW/SHEAR AND WEAK
INSTABILITY SHOULD LIMIT OVERALL STORM ORGANIZATION.

HIGH-BASED TSTMS ALSO APPEAR LIKELY TO FORM NEAR THE STALLED
BOUNDARY ACROSS NERN CO LATER TODAY. A FEW OF THESE STORMS MAY
PERSIST ALONG AND NEAR THE FRONT WHILE SPREADING EAST TOWARD GREATER
DOWNSTREAM INSTABILITY ACROSS NEB/NRN KS THIS EVENING. THERMODYNAMIC
ENVIRONMENT SHOULD INITIALLY SUPPORT STRONG TO DAMAGING WINDS FROM
THIS CONVECTION. WITH TIME...ANY STORMS NEAR AND NORTH OF THE FRONT
WILL EXIST AMIDST STRONG BUOYANCY...RELATIVELY LOWER LFC... AND
BACKED/ELY BOUNDARY LAYER FLOW. THESE FACTORS WOULD FAVOR BETTER
STORM ORGANIZATION/PERSISTENCE...PERHAPS IN THE FORM OF A COUPLE
SUPERCELLS WITH HAIL...WIND...AND BRIEF TORNADO POTENTIAL.

...NRN ROCKIES...
A SMALL CLUSTER OF HIGH-BASED/DRY TSTMS MAY ACCOMPANY THE SHORT WAVE
TROUGH DEVELOPING NEWD ACROSS SWRN MT THROUGH THE AFTERNOON. A DEEP
BOUNDARY LAYER AND DRY SUB-CLOUD AIRMASS WILL CONTRIBUTE TO DAMAGING
WIND POTENTIAL WITH THESE STORMS. OVERALL COVERAGE OF SEVERE THREAT
SHOULD REMAIN LIMITED AND WARRANT ONLY LOW SEVERE PROBABILITIES AT
THIS TIME.

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