Tuesday, May 31, 2011

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 311959
SWODY1
SPC AC 311957

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0257 PM CDT TUE MAY 31 2011

VALID 312000Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND TONIGHT
ACROSS THE GREAT LAKES REGION...

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND EVE ACROSS
PARTS OF THE SRN HIGH PLAINS...

...20Z UPDATE...

...GREAT LAKES REGION...
WITHIN THE WARM SECTOR OF A DEEP SURFACE CYCLONE NOW MIGRATING
ACROSS SOUTHEASTERN MANITOBA INTO NORTHWEST ONTARIO...18Z RAOBS
ACROSS LOWER MICHIGAN EXHIBIT PROFILES CHARACTERIZED BY FAIRLY STEEP
LAPSE RATES AND MODERATELY LARGE MIXED LAYER CAPE /1000-2000 J PER
KG/ IN THE PRESENCE OF A SHEARED AND MODESTLY STRONG WESTERLY DEEP
LAYER MEAN FLOW /ON THE ORDER OF 40 KT/. SOME STRENGTHENING OF WIND
FIELDS APPEARS LIKELY AS THE BROADER SCALE UPSTREAM CLOSED
LOW/TROUGH CONTINUES TO LIFT NORTHEASTWARD LATE THIS AFTERNOON AND
EVENING...BUT FORCING AND FOCUS FOR CONVECTIVE REMAINS UNCLEAR.
LOW-LEVEL CONVERGENCE SOUTH OF THE INTERNATIONAL BORDER AREA REMAINS
WEAK. HOWEVER...IT STILL APPEARS THAT FORCING ASSOCIATED WITH A
SMALLER SCALE IMPULSE LIFTING NORTHEAST OF THE UPPER MISSISSIPPI
VALLEY...TOWARD THE UPPER GREAT LAKES REGION... COULD CONTRIBUTE TO
OR ENHANCE CONVECTIVE DEVELOPMENT LATE THIS AFTERNOON. WHILE SEVERE
PROBABILITIES HAVE BEEN LOWERED BELOW THE MODERATE RISK THRESHOLD
DUE TO INCREASING UNCERTAINTIES CONCERNING POTENTIAL STORM
COVERAGE...THE ENVIRONMENT ACROSS PORTIONS OF NORTHERN/EASTERN LOWER
MICHIGAN APPEARS LIKE IT COULD SUPPORT STRONG GUSTS IN EXCESS OF 65
KT WITH ANY SUSTAINED STORMS SPREADING ACROSS THE REGION LATE THIS
AFTERNOON AND EVENING. IT ALSO DOES NOT APPEAR OUT OF THE QUESTION
THAT CONVECTION COULD EVENTUALLY CONSOLIDATE INTO AN ORGANIZED STORM
CLUSTER CAPABLE OF PRODUCING STRONG WIND GUSTS ACROSS AND TO THE LEE
OF THE LOWER GREAT LAKES LATER TONIGHT.

...SOUTHERN HIGH PLAINS...
MODELS CONTINUE TO SUGGEST THAT SCATTERED BOUNDARY LAYER BASED STORM
DEVELOPMENT WILL OCCUR LATE THIS AFTERNOON AND EVENING. THE FOCUS
IS UNCLEAR...BUT SLIGHT RISK PROBABILITIES WILL BE MAINTAINED FOR
NOW...ADJUSTED TO WHERE BETTER BOUNDARY LAYER DESTABILIZATION IS
WELL UNDERWAY.

..KERR.. 05/31/2011

.PREV DISCUSSION... /ISSUED 1101 AM CDT TUE MAY 31 2011/

A POWERFUL UPPER TROUGH OVER THE MIDWEST WILL ROTATE QUICKLY
EASTWARD INTO THE GREAT LAKES REGION TODAY. MEANWHILE...AN
ASSOCIATED 80-90 KNOT MID LEVEL JET WILL NOSE INTO MI. THE RESULT
WILL BE THE POTENTIAL FOR AN ACTIVE SEVERE WEATHER EVENT ACROSS
PORTIONS OF THE GREAT LAKES STATES.

VISIBLE SATELLITE IMAGERY SHOWS STRONG HEATING IS OCCURRING OVER
MUCH OF MI. SURFACE DEWPOINTS IN THE 60S...COUPLED WITH AFTERNOON
HIGH TEMPERATURES IN THE MID 80S WILL YIELD MLCAPE VALUES AROUND
3000 J/KG. THIS COMBINED WITH THE STRENGTHENING LOW TO MID LEVEL
WIND FIELDS WILL PROVIDE A VERY FAVORABLE THERMODYNAMIC AND SHEAR
ENVIRONMENT FOR ORGANIZED SEVERE STORMS. THE PRIMARY FORECAST
PROBLEM TODAY INVOLVES THE MODE OF THE CONVECTION.

IT APPEARS LIKELY THAT SCATTERED THUNDERSTORMS WILL FORM BY EARLY
AFTERNOON OVER PORTIONS OF EASTERN WI AND UPPER MI...SPREADING
QUICKLY EASTWARD ACROSS LAKE MI INTO LOWER MI. MORNING MESOSCALE
AND OPERATIONAL MODELS DIFFER ON EVOLUTION OF CONVECTION... RANGING
FROM A FAST-MOVING BOW ECHO TO BROKEN LINE OF SEVERE STORMS. ALSO
NEW GUIDANCE SUGGESTS CORRIDOR MOST LIKELY TO HAVE WIDESPREAD SEVERE
STORMS HAS SHIFTED SOUTHWARD INTO CENTRAL/SOUTHERN LOWER MI AND
PERHAPS NORTHERN OH. GIVEN THE STRENGTH OF THE WIND FIELDS...HAVE
OPTED TO MAINTAIN THE MODERATE RISK DESPITE UNCERTAINTIES.
WIDESPREAD DAMAGING WINDS ARE A DISTINCT POSSIBILITY IF THE RIGHT
CONVECTIVE EVOLUTION OCCURS.

THE REMNANTS OF THIS MCS WILL TRACK INTO ONTARIO AND LIKELY WEAKEN.
HOWEVER...THERE IS SOME POTENTIAL FOR THIS SYSTEM TO MOVE AS FAR
EAST AS NORTHERN NY OVERNIGHT. THIS AREA WILL NEED TO BE MONITORED
IN LATER OUTLOOK UPDATES.

...TX/NM/OK...
STRONG DAYTIME HEATING WILL OCCUR THIS AFTERNOON OVER PORTIONS OF
WEST TX...WITH SOUTHEASTERLY LOW LEVEL WINDS RETURNING RICH MOISTURE
INTO REGION. BY EARLY EVENING...MODERATE CAPE WITH WEAK CINH ARE
EXPECTED ALONG AND SOUTH OF THE RETREATING WEAK SURFACE BOUNDARY.
MID LEVEL HEIGHTS WILL BE RISING ACROSS THIS REGION THROUGH THE
PERIOD...BUT A CONCENSUS OF MODEL SOLUTIONS INDICATES THAT SCATTERED
THUNDERSTORMS WILL FORM DURING THE LATE AFTERNOON AND EVENING HOURS.
THOSE STORMS THAT FORM WILL BE IN AN ENVIRONMENT OF SUFFICIENT
DEEP-LAYER EFFECTIVE SHEAR SUPPORTIVE FOR SUPERCELLS. STEEP LOW AND
MID LEVEL LAPSE RATES WILL PROMOTE A RISK OF LARGE HAIL AND DAMAGING
WINDS.

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