DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 222002
SWODY1
SPC AC 221959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SAT JUN 22 2013

VALID 222000Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NORTH
CENTRAL ROCKIES...MUCH OF THE NORTHERN AND CENTRAL PLAINS...INTO
PARTS OF THE UPPER MISSISSIPPI VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SOUTHERN HIGH
PLAINS...

...SOUTHERN HIGH PLAINS...
PRIMARY OUTLOOK ADJUSTMENT IS THE ADDITION OF A CATEGORICAL SLIGHT
RISK FOR HAIL/WIND POTENTIAL ACROSS PARTS OF WEST/NORTHWEST
TX...WITH MORE ISOLATED STORMS ALSO ANTICIPATED ACROSS FAR SOUTHWEST
TX. AIDED BY A WEAK MID-LEVEL IMPULSE APPROACHING FROM NM/SOUTHERN
CO...AT LEAST ISOLATED INSTANCES OF HAIL/WIND ARE EXPECTED
ESPECIALLY LATE THIS AFTERNOON/EARLY EVENING.

...ELSEWHERE...
SEE PRIOR OUTLOOK DISCUSSION BELOW AND EXISTING/SUBSEQUENT MESOSCALE
DISCUSSIONS FOR ADDITIONAL DETAILS.

..GUYER.. 06/22/2013

.PREV DISCUSSION... /ISSUED 1126 AM CDT SAT JUN 22 2013/

...SYNOPSIS...
TO THE SOUTH OF A REMNANT BLOCKING PATTERN OVER WESTERN AND CENTRAL
CANADA...A MODEST BELT OF WESTERLIES CONTINUES TO CURVE ACROSS THE
PACIFIC COAST THROUGH THE ROCKIES. A NUMBER OF SHORT WAVE TROUGHS
ARE EMBEDDED WITHIN THE REGIME...INCLUDING ONE SIGNIFICANT IMPULSE
NOW TURNING EASTWARD INTO THE NORTHERN/CENTRAL ROCKIES. THIS LATTER
FEATURE IS EXPECTED TO PROGRESS NORTHEASTWARD ACROSS THE ROCKIES
INTO THE NORTHERN HIGH PLAINS BY EARLY SUNDAY...PRECEDED BY AT LEAST
A COUPLE OF SMALLER SCALE IMPULSES WITHIN INCREASINGLY CYCLONIC
SOUTHWESTERLY MID/UPPER FLOW ACROSS THE NORTHERN AND CENTRAL PLAINS.
MEANWHILE...A COUPLE OF PERTURBATIONS...NOW PROGRESSING INTO
BROADER SCALE ANTICYCLONIC FLOW ACROSS THE UPPER MISSISSIPPI VALLEY
INTO THE GREAT LAKES...WILL CONTINUE EASTWARD TODAY...AND THE
TENDENCY MAY BE FOR MID-LEVEL HEIGHTS TO RISE ACROSS THE UPPER
MIDWEST...BEFORE FALLING MORE SUBSTANTIVELY AGAIN LATE TONIGHT INTO
SUNDAY.

THIS EVOLVING PATTERN IS AGAIN EXPECTED TO SUPPORT CONSIDERABLE
THUNDERSTORM ACTIVITY TODAY AND TONIGHT ACROSS THE NORTHERN ROCKIES
INTO THE UPPER MIDWEST...WITH INCREASING CHANCES FOR THUNDERSTORM
ACTIVITY ALSO EASTWARD ACROSS THE GREAT LAKES REGION INTO PARTS OF
THE NORTHEAST. STRONG HEATING MAY ALSO AGAIN CONTRIBUTE TO
SCATTERED STORM DEVELOPMENT LATE THIS AFTERNOON AND EVENING ACROSS
PARTS OF THE SOUTHERN HIGH PLAINS

OTHERWISE...WITH MID-LEVEL INHIBITION REMAINING RELATIVELY WEAK EAST
OF THE MISSISSIPPI VALLEY...SCATTERED THUNDERSTORM ACTIVITY IS ALSO
EXPECTED AROUND THE PERIPHERY OF A LINGERING WEAK UPPER LOW CENTERED
NEAR THE SOUTHERN APPALACHIANS...ACROSS PARTS OF THE LOWER OHIO
VALLEY INTO THE OZARK PLATEAU...AND ACROSS THE GULF AND SOUTH
ATLANTIC COASTS.

...NRN/CNTRL ROCKIES EASTWARD TO UPPER MIDWEST...
THE DETAILS OF POTENTIAL CONVECTIVE DEVELOPMENT FOR TODAY REMAIN A
BIT UNCLEAR. THE PRIMARY SURFACE BOUNDARY OF INTEREST APPEARS TO BE
A COMPOSITE OUTFLOW BOUNDARY GENERATED BY STORM CLUSTERS OF THE PAST
COUPLE OF DAYS...WHICH NOW GENERALLY EXTENDS ACROSS LOWER
MICHIGAN...NORTHERN INDIANA AND ILLINOIS...THROUGH SOUTHERN
IOWA...AND THE VICINITY OF THE KANSAS/NEBRASKA BORDER...INTO THE
COLORADO FRONT RANGE. MODIFICATION AND NORTHWARD RETREAT OF THIS
BOUNDARY IS UNCERTAIN...BUT STEEPEST MID-LEVEL LAPSE RATES...EAST OF
THE HIGH PLAINS...HAVE GENERALLY BECOME FOCUSED IN A CORRIDOR ALONG
AND TO ITS NORTH. MID-LEVEL LAPSE RATES REMAIN MODESTLY STEEP
NORTHWARD THROUGH MUCH OF THE DAKOTAS...BUT CONSIDERABLE OVERTURNING
HAS STABILIZED A SIGNIFICANT PORTION OF THE UPPER MISSISSIPPI VALLEY
AND UPPER GREAT LAKES REGION. WHERE MID-LEVEL LAPSE RATES REMAIN
STEEP...THE BOUNDARY LAYER ALSO REMAINS MOIST TO THE NORTH OF THE
FRONT...BENEATH MODEST SOUTHWESTERLY MID-LEVEL FLOW...WHICH WILL
CONTRIBUTE TO SUFFICIENT SHEAR FOR ORGANIZED STORM DEVELOPMENT
ACROSS A BROAD AREA OF THE NORTH CENTRAL U.S. BY LATE AFTERNOON.

IN ADDITION TO THE OUTFLOW BOUNDARY...THE LOW-LEVEL UPSLOPE FLOW
REGIME ACROSS THE NORTH CENTRAL HIGH PLAINS IS EXPECTED TO PROVIDE
ANOTHER FOCUS FOR RELATIVELY HIGHER SEVERE STORM PROBABILITIES.
AIDED BY FORCING ASSOCIATED WITH THE UPPER IMPULSE...DISCRETE STORM
DEVELOPMENT IS EXPECTED TO INCREASE THROUGH THE AFTERNOON ACROSS
PARTS OF CENTRAL INTO EASTERN WYOMING/NORTHEAST COLORADO AND
ADJACENT WESTERN NEBRASKA AND THE WESTERN DAKOTAS. STRONGEST STORMS
WILL BE CAPABLE OF PRODUCING VERY LARGE HAIL...PERHAPS A COUPLE OF
TORNADOES...BEFORE ACTIVITY GROWS UPSCALE WITH A MORE PROMINENT RISK
FOR DAMAGING WIND GUSTS AS IT SPREADS EASTWARD INTO THE PLAINS THIS
EVENING.

...SOUTHERN GREAT LAKES REGION/OHIO VALLEY...
MODERATE BOUNDARY LAYER DESTABILIZATION DOES APPEAR PROBABLE WITH
DAYTIME HEATING...ALONG AND SOUTH OF THE OUTFLOW BOUNDARY ACROSS THE
SOUTHERN GREAT LAKES REGION INTO THE OHIO VALLEY. THIS MAY BE
ENOUGH TO SUPPORT SMALL CLUSTERS OF STORMS WITH AT LEAST LOW
PROBABILITIES FOR SEVERE WIND/HAIL. HOWEVER...DUE TO THE WEAK
NATURE OF THE FLOW FIELDS...SEVERE POTENTIAL STILL APPEARS TOO LOW
FOR A SLIGHT RISK AT THE PRESENT TIME.

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