SWODY2
SPC AC 301729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT MON MAY 30 2011
VALID 311200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS TUE ACROSS PARTS OF THE UPPER
MIDWEST/GREAT LAKES REGION...
...SYNOPSIS...
MID-LEVEL SUBTROPICAL RIDGING NOW PRESENT ACROSS MUCH OF THE EASTERN
U.S...SOUTHWESTWARD INTO THE MEXICAN PLATEAU...APPEARS LIKELY TO
REMAIN GENERALLY STRONG THROUGH THIS FORECAST PERIOD.
HOWEVER...MODELS STILL INDICATE THAT ONE IN A SERIES OF CLOSED
LOWS/SHORT WAVE TROUGHS WILL CONTINUE PROGRESSING WITHIN SEASONABLY
STRONGER FLOW AROUND ITS WESTERN AND NORTHERN PERIPHERY.
THE CYCLONIC CIRCULATION CENTER ASSOCIATED WITH THIS LATTER FEATURE
IS PROGGED TO SHIFT INTO AREAS NEAR OR JUST NORTH OF THE NORTH
DAKOTA/SASKATCHEWAN BORDER AREA AT 12Z TUESDAY...BEFORE
WEAKENING/BROADENING AND ACCELERATING EAST NORTHEASTWARD INTO
NORTHERN ONTARIO BY 12Z WEDNESDAY. THIS IS EXPECTED TO OCCUR AS A
SMALLER SCALE SHORT WAVE IMPULSE PIVOTS AROUND ITS SOUTHERN/ EASTERN
PERIPHERY...THROUGH THE UPPER MISSISSIPPI VALLEY/GREAT LAKES REGION
DURING THE DAY TUESDAY...INTO WESTERN QUEBEC BY THE END OF THE
PERIOD.
SOUTH OF A BROAD DEEP SURFACE CYCLONE ACCOMPANYING THE UPPER LOW...A
COLD FRONT WILL ADVANCE THROUGH MUCH OF THE UPPER MIDWEST/GREAT
LAKES/OHIO AND MIDDLE MISSISSIPPI VALLEY REGION. HOWEVER...THE
FRONT/PRE-FRONTAL DRY LINE ACROSS THE CENTRAL AND SOUTHERN PLAINS
LIKELY WILL WEAKEN AND LIFT NORTHWARD/RETREAT WESTWARD...AS THE
CENTER OF RIDGING ALOFT SHIFTS WEST OF THE LOWER MISSISSIPPI
VALLEY...AND ANOTHER CLOSED LOW/SHORT WAVE TROUGH DIGS INTO THE
PACIFIC COAST.
...UPPER MIDWEST/GREAT LAKES REGION...
REMNANTS OF CONSIDERABLE DAY 1 CONVECTIVE DEVELOPMENT MAY BE IN THE
PROCESS OF SPREADING ACROSS MUCH OF THE UPPER HALF OF THE
MISSISSIPPI VALLEY EARLY TUESDAY. AND THE INFLUENCE OF ASSOCIATED
CLOUD COVER AND PRECIPITATION ON SUBSEQUENT DOWNSTREAM PRE-FRONTAL
DESTABILIZATION REMAINS UNCLEAR. STRONGER LOW-LEVEL CONVERGENCE
ALSO APPEARS LIKELY TO REMAIN FOCUSED NORTH OF THE INTERNATIONAL
BORDER AREA THROUGH THE PERIOD...WHICH MAY ALSO SUBSTANTIALLY IMPACT
THE CONVECTIVE POTENTIAL.
HOWEVER...THE WARM SECTOR BOUNDARY LAYER SHOULD BE SEASONABLY MOIST
/UPPER 60S NEAR 70F SURFACE DEW POINTS/...AND INSOLATION PROBABLY
WILL BE SUFFICIENT TO CONTRIBUTE TO MODERATE CAPE BY THE AFTERNOON.
COUPLED WITH FAVORABLE MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION
EXPECTED TO SPREAD ACROSS EASTERN WISCONSIN AND MICHIGAN NEAR AND
AFTER PEAK HEATING...THIS SHOULD BE SUFFICIENT TO INITIATE NEW
CONVECTIVE DEVELOPMENT. IN THE PRESENCE OF SHEARED 40+ KT WESTERLY
DEEP LAYER MEAN FLOW FIELDS /STRONGEST NEAR AND NORTH OF THE
INTERNATIONAL BORDER/...ISOLATED SUPERCELLS WILL BE POSSIBLE BEFORE
UPSCALE CONVECTIVE GROWTH INTO ONE OR MORE ORGANIZED CONVECTIVE
LINES OR CLUSTERS OCCURS. DAMAGING WIND GUSTS AND HAIL APPEAR THE
PRIMARY SEVERE THREATS...BUT TORNADOES WILL BE POSSIBLE...BEFORE THE
THREAT DIMINISHES/SPREADS INTO ONTARIO TUESDAY EVENING.
...LEE OF THE LWR GREAT LAKES/OH VLY INTO S ATLC COAST STATES...
DAYTIME HEATING OF A VERY MOIST BOUNDARY LAYER IS EXPECTED TO YIELD
MODERATE TO STRONG CAPE BY TUESDAY AFTERNOON BENEATH UPPER RIDGING.
ALTHOUGH FORCING REMAINS UNCERTAIN...AND SHEAR WILL BE
WEAK...THERMODYNAMIC PROFILES SHOULD BE SUPPORTIVE OF AT LEAST LOW
SEVERE PROBABILITIES...WITH THE BEST CHANCE FOR SCATTERED STORM
DEVELOPMENT ON THE PERIPHERY OF THE WEAKENING MID-LEVEL HIGH CENTER.
..KERR.. 05/30/2011
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