Monday, June 21, 2010

DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 211713
SWODY2
SPC AC 211712

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1212 PM CDT MON JUN 21 2010

VALID 221200Z - 231200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE PLAINS TO THE
MID-ATLANTIC COAST...

...SYNOPSIS...
MODEST BELT OF WESTERLIES WILL CONTINUE ACROSS THE NRN THIRD OF THE
COUNTRY ON TUESDAY AS THE SUBTROPICAL HIGH EXPANDS ACROSS THE SOUTH.
A PRIMARY UPPER TROUGH...CURRENTLY OVER THE INTERMOUNTAIN
WEST...WILL EJECT ENE TOWARD THE CENTRAL/NORTHERN PLAINS BY TUESDAY
NIGHT. PRECEDING THIS SYSTEM...SEVERAL LOWER-AMPLITUDE IMPULSES
WILL MOVE FROM THE MISSOURI VALLEY INTO THE MID-ATLANTIC REGION.

...PLAINS TO THE MID-ATLANTIC COAST...
THE WAVE TRAIN OF MCS/S WILL CONTINUE OVER A BROAD AREA ALONG/N OF
AN E-W ORIENTED BAROCLINIC ZONE ACROSS THE REGION THROUGH TUESDAY.
ALTHOUGH THE TIMING OF EACH MCS AND INCIPIENT CONVECTIVE-INDUCED
IMPULSE WILL BE DIFFICULT... MODEL GUIDANCE DOES OFFER SOME
CONSISTENCY/AGREEMENT IN HIGHLIGHTING AT LEAST THREE MAIN CORRIDORS
OF SEVERE POTENTIAL...THE MID-ATLANTIC REGION...THE MIDWEST AND THE
CENTRAL PLAINS TO THE CORN BELT.

1/ MID-ATLANTIC COAST TUESDAY AFTERNOON/EVENING...
THUNDERSTORMS CURRENTLY DEVELOPING ALONG THE MS RIVER IN ERN IA/WRN
IL WILL LIKELY BE ONGOING OVER THE UPPER OH VALLEY AT 12Z TUESDAY.
ZONE OF ENHANCED WARM ADVECTION ALONG THE NOSE OF A WSW LOW-LEVEL
JET WILL MAINTAIN THREAT OF STORMS THROUGH THE DAY TUESDAY
DOWNSTREAM INTO NY AND THE MID-ATLANTIC REGION. STRONGEST LOW-LEVEL
DESTABILIZATION WILL LIKELY OCCUR FROM ERN PA SWD INTO NRN/WRN VA
ALONG THE SRN FRINGE OF 40 KT MID-LEVEL FLOW. AS A RESULT...A FEW
STORMS MAY ORGANIZE ALONG RESIDUAL OUTFLOWS FROM EARLY DAY ACTIVITY
AND ALONG THE TERRAIN WITH RISKS FOR STRONG WINDS/HAIL.
SEVERE/STORM PROBABILITIES WILL WANE DURING THE EVENING AND WITH EWD
EXTENT.

2/ MIDWEST TUESDAY LATE MORNING INTO EVENING...
THUNDERSTORMS THAT DEVELOP ACROSS THE CENTRAL/NRN HIGH PLAINS IN
ASSOCIATION WITH THE UPPER-LEVEL JET STREAK APPROACHING THE REGION
TODAY WILL BE ONGOING AS AN MCS OVER THE MID-MISSOURI VALLEY EARLY
TUESDAY MORNING. AIR MASS DOWNSTREAM ACROSS ERN IA...IL AND IND IS
EXPECTED TO BECOME UNSTABLE WITH MLCAPES TO 2500 J/KG BY TUESDAY
AFTERNOON. EXPECT THAT FORWARD FLANKS OF THE MORNING ACTIVITY WILL
FLARE-UP AGAIN DURING THE MID-DAY HOURS WITH SUBSEQUENT UPSCALE
DEVELOPMENT INTO BOW ECHOES AS 45-50 KTS OF MID-LEVEL FLOW SPREADS
SEWD. ACTIVITY WILL PROBABLY REACH PARTS OF OH/NRN KY BY LATE
EVENING WITH WANING SEVERE PROBABILITIES.

3/ CENTRAL PLAINS TO THE CORN BELT TUESDAY LATE AFTERNOON/NIGHT...
COMPARATIVELY STRONGER FLOW/INSTABILITY WILL EVOLVE ACROSS THIS
REGION TUESDAY AFTERNOON/NIGHT AS PRESENCE OF VERY STEEP LAPSE
RATES/VERY MOIST BOUNDARY LAYER COMBINE WITH THE EJECTION OF THE
PRIMARY UPPER TROUGH. AIR MASS BEHIND DEPARTING MORNING STORMS WILL
HAVE NO PROBLEM RECOVERING WITH AFTERNOON MLCAPES TO 3500 J/KG
ACROSS THE CENTRAL/NRN PLAINS. INHIBITION WILL PROBABLY KEEP STORM
DEVELOPMENT SUPPRESSED UNTIL STRONG POSITIVE VORTICITY ADVECTION
OVERSPREADS THE REGION LATE IN THE AFTERNOON. STORMS WILL FIRST
DEVELOP OVER THE HIGH PLAINS OF ERN WY/SW SD AND MAY INCLUDE
HIGH-BASED SUPERCELLS WITH LARGE HAIL LATE AFTERNOON. UPSCALE
DEVELOPMENT OF AN EVENING/NIGHTTIME MCS APPEARS LIKELY OVER PARTS OF
SD AND NEB ALONG/N OF A SURGING COLD FRONT. GIVEN PRESENCE OF 55-65
KT OF WLY MID-LEVEL FLOW...MAGNITUDE OF INSTABILITY AND DEGREE OF
FORCING SHOULD CONTRIBUTE TO AN ORGANIZED NIGHTTIME MCS OVER MUCH OF
SD...NEB AND POINTS EWD TO THE UPPER MS VALLEY BY 12Z WEDNESDAY.
HIGH WINDS AND HAIL CAN BE EXPECTED.

..RACY.. 06/21/2010

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