SWODY2
SPC AC 281729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT SAT MAY 28 2011
VALID 291200Z - 301200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN GREAT LAKES...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS
AND UPPER MS VALLEY...
...SYNOPSIS...
MODELS CONTINUE TO INDICATE THE UPPER RIDGE UNDERGOING FURTHER
AMPLIFICATION OVER THE ERN HALF OF THE U.S. WHILE AN UPSTREAM TROUGH
MOVES EWD THROUGH THE GREAT BASIN REGION TOWARD THE ROCKIES. A
STRONG JET STREAK/SHORTWAVE TROUGH WILL ROTATE THROUGH UPPER TROUGH
BASE AND INTO THE CENTRAL ROCKIES LATE SUNDAY NIGHT ACCOMPANIED BY A
PACIFIC COLD FRONT. AT 12Z SUNDAY...A WARM FRONT SHOULD EXTEND FROM
SRN KS THROUGH THE MID MS VALLEY TO LOWER GREAT LAKES REGION. SLY
LOW LEVEL FLOW EXTENDING INTO THE CENTRAL U.S. WILL SUPPORT A NWD
MOVEMENT OF A PORTION OF THIS BOUNDARY THROUGH THE LOWER MO VALLEY
TO SRN IA BY 30/00Z. FURTHER NWD MOVEMENT OF THE FULL EXTENT OF THE
WARM FRONT IS EXPECTED SUNDAY NIGHT WITH THIS BOUNDARY EXTENDING
FROM NRN NEB TO SRN MN AND CENTRAL LOWER MI BY 12Z MONDAY. A
DRYLINE SHOULD EXTEND SWD FROM THE WARM FRONT IN SWRN KS THROUGH WRN
OK TO WRN TX SUNDAY AFTERNOON.
...OH VALLEY THROUGH GREAT LAKES AND NERN STATES...
THE PORTION OF THE WARM FRONT EXTENDING ALONG SRN PORTIONS OF THE
GREAT LAKES EARLY SUNDAY SHOULD REMAIN QUASI-STATIONARY INTO SUNDAY
AFTERNOON...BEFORE LIFTING NWD SUNDAY NIGHT. A FEW ELEVATED STORMS
MAY BE IN PROGRESS NORTH OF THIS BOUNDARY AND COULD POSE A THREAT
FOR HAIL. WARM SECTOR SHOULD DESTABILIZE IN THE WAKE OF SUNDAY
MORNING ACTIVITY...AS RICHER MOISTURE /SURFACE DEWPOINTS IN THE 60S/
AND EML PLUME ADVECT NEWD DURING THE DAY. A SLOWLY BUILDING UPPER
RIDGE AND INCREASING CONVECTIVE INHIBITION SUGGEST THE WARM SECTOR
WILL BECOME INCREASINGLY HOSTILE TO SURFACE BASED STORMS...AND BEST
CHANCE FOR STORM INITIATION WILL LIKELY REMAIN IN COOL SECTOR NORTH
OF WARM FRONT. HOWEVER...MODELS CONTINUE TO INDICATE SOME CONCERN
THAT A WINDOW MAY EXIST FOR SURFACE BASED STORMS TO DEVELOP ALONG
THE BOUNDARY BEFORE THE WARMER EML PLUME ARRIVES. IF THIS OCCURS
0-6 KM VERTICAL SHEAR FROM 35-40 KT AND MODERATE INSTABILITY WILL
SUPPORT A THREAT FOR ORGANIZED STORMS INCLUDING SUPERCELLS INTO THE
AFTERNOON. THUS THIS OUTLOOK WILL MAINTAIN A SLIGHT RISK TO INCLUDE
THE POSSIBILITY OF LARGE HAIL WITH ELEVATED STORMS AS WELL AS A
SOMEWHAT CONDITIONAL THREAT OF SURFACE BASED STORMS.
...CNTRL AND NRN PLAINS THROUGH MID-UPPER MS VALLEY...
ELEVATED STORMS WILL BE ONGOING EARLY SUNDAY NORTH OF WARM FRONT
OVER THE CNTRL PLAINS AND MID MS VALLEY. STRONGER STORMS COULD POSE
A THREAT FOR HAIL. ACTIVITY WILL LIKELY WEAKEN AS IT SHIFTS NNEWD
DURING THE DAY ALONG ERN/NERN EXTENT OF AN EXPANSIVE WARM EML /700
MB TEMPERATURES FROM 12-14C/ ADVECTS NEWD AND EFFECTIVELY CAPPING
THE WARM SECTOR...AND POSSIBLY A PORTION OF THE COOL SECTOR AS WELL.
NWD ADVECTION OF RICHER /MID 60S DEWPOINTS/ BENEATH THE STEEP LAPSE
RATE PLUME WILL RESULT IN MODERATE MUCAPE AND NWD DESTABILIZATION
WITH TIME. STRENGTH OF CAP SUGGESTS SURFACE BASED CONVECTIVE
INITIATION ALONG WARM FRONT OR ANY RESIDUAL OUTFLOW BOUNDARIES WILL
BE DIFFICULT. ADDITIONAL STORMS SHOULD DEVELOP LATER SUNDAY NIGHT
OVER A PORTION OF THE NRN PLAINS AND UPPER MS VALLEY WITHIN ZONE OF
ISENTROPIC LIFT NORTH OF WARM FRONT AS LLJ STRENGTHENS. ISOLATED
LARGE HAIL WILL BE POSSIBLE WITH THIS ACTIVITY. THIS OUTLOOK HAS
EXPANDED THE AREAL COVERAGE OF THIS THREAT TO INCLUDE MORE OF ERN SD
AND SRN MN.
...SRN HIGH PLAINS OF NWRN TX THROUGH WRN OK AND SWRN KS...
DEEP MIXING IN VICINITY OF DRYLINE WILL SUPPORT THREAT OF A FEW HIGH
BASED STORMS FROM A PORTION OF WRN TX...WRN OK INTO SWRN KS WHERE
THE ATMOSPHERE WILL BECOME MODERATELY UNSTABLE. HIGH BASED NATURE OF
THE CONVECTION AND MODEST VERTICAL SHEAR SUGGEST THE PRIMARY THREATS
WILL BE ISOLATED DAMAGING WIND AND LARGE HAIL. ANY STORMS THAT
DEVELOP SHOULD DIMINISH BY MID EVENING AS CONVECTIVE INHIBITION
INCREASES WITH LOSS OF DIABATIC HEATING.
...ERN WY...
MOIST UPSLOPE FLOW INTO SERN WY PER LOW LEVEL ELY WINDS N OF WARM
FRONT SHOULD BE SUPPORTING STRATUS/FOG AT THE START OF DAY 2.
CONTINUED MOISTURE ADVECTION INTO THIS REGION BENEATH STEEPENING
LAPSE RATES WITH APPROACH OF GREAT BASIN TROUGH WILL SUPPORT
DESTABILIZATION. 12Z NAM SUGGESTS THE LOW STRATUS/FOG WILL BE VERY
SLOW TO DISSIPATE AND THUS WOULD LIMIT STRONGER SURFACE HEATING AND
THE DEVELOPMENT OF STRONGER INSTABILITY. HOWEVER...IF CLOUDS
DISSIPATE EARLY IN THE PERIOD...THEN THE COMBINATION OF FAVORABLE
UPSLOPE FLOW AND THE APPROACH OF THE PACIFIC COLD FRONT WILL PROVE
SUPPORTIVE OF TSTM DEVELOPMENT. INCREASING EFFECTIVE BULK SHEAR TO
40-50 KT WILL FAVOR SUPERCELLS WITH ALL FACETS OF SEVERE WEATHER
POSSIBLE AS STORMS DEVELOP AND SPREAD TOWARD WRN SD/NEB SUNDAY
EVENING.
..PETERS.. 05/28/2011
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