Saturday, June 9, 2012

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 091626
SWODY1
SPC AC 091624

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1124 AM CDT SAT JUN 09 2012

VALID 091630Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM LATE THIS AFTERNOON INTO
EARLY SUNDAY ACROSS PORTIONS OF THE NRN PLAINS INTO UPPER MS
VALLEY...

...SYNOPSIS...

POTENT VORTICITY MAXIMUM AND ASSOCIATED MID AND UPPER-LEVEL JET
STREAKS FROM NRN CA INTO NRN GREAT BASIN WILL TRANSLATE EWD/NEWD
INTO THE NRN HIGH PLAINS...CONTRIBUTING TO THE EWD PROGRESSION AND
AMPLIFICATION OF LARGE-SCALE UPPER TROUGH OVER THE SAME GENERAL
AREA. FARTHER S...AN UPPER LOW OVER THE NWRN GULF OF MEXICO WILL
DEVELOP NEWD INTO THE LOWER MS VALLEY...WHILE ELSEWHERE A
LOW-AMPLITUDE PERTURBATION MOVES FROM LAKE HURON SEWD THROUGH THE
LOWER GREAT LAKES.

AT THE SURFACE...LOW PRESSURE OVER CNTRL ND WILL DEVELOP NNEWD INTO
CNTRL MANITOBA WHILE TRAILING COLD FRONT PUSHES EWD/SEWD THROUGH THE
WRN/CNTRL DAKOTAS AND CNTRL HIGH PLAINS.
MEANWHILE...QUASI-STATIONARY FRONT SITUATED ALONG THE GULF COAST
INTO CNTRL FL PENINSULA WILL LIFT SLOWLY NWD IN RESPONSE TO NEWD
PROGRESSION OF UPPER SYSTEM.

...NRN PLAINS INTO UPPER MS VALLEY...

12Z REGIONAL SOUNDINGS SHOWED THE PRESENCE OF VERY STEEP MIDLEVEL
LAPSE RATES /I.E. 8.5-9.5 C PER KM IN THE 700-500-MB LAYER/ ATOP A
MODESTLY MOIST BOUNDARY LAYER WHICH WILL CONTRIBUTE TO A MODERATELY
UNSTABLE ENVIRONMENT LATER TODAY WITH MLCAPE INCREASING TO 1000-2500
ACROSS PRE-FRONTAL WARM SECTOR. CAPPING AT THE BASE OF THE EML WILL
LIKELY INHIBIT SURFACE-BASED TSTM DEVELOPMENT THROUGH MOST OF THE
AFTERNOON...WITH THE PROBABILITY OF INITIATION INCREASING BY 10/00Z.
BY THIS TIME...CONVERGENCE WILL BEGIN TO INCREASE ALONG THE FRONT
OWING TO THE ONSET OF NOCTURNAL LOW-LEVEL WIND MAXIMUM DEVELOPMENT.

IN THE PRESENCE OF A GRADUALLY STRENGTHENING MID AND UPPER-LEVEL
WIND FIELD...VERTICAL SHEAR WILL BECOME SUFFICIENTLY STRONG FOR
SUPERCELLS AS THE INITIAL STORM MODE WITH AN ATTENDANT RISK FOR
DAMAGING WINDS AND LARGE HAIL. THIS ACTIVITY MAY GROW UPSCALE INTO
ONE OR MULTIPLE STORM CLUSTERS WITH THE WIND/HAIL THREAT CONTINUING
INTO EARLY SUNDAY.

...CNTRL/ERN GULF COAST...

LOW-LEVEL WAA/MOISTURE TRANSPORT INVOF WARM FRONT WILL SUSTAIN
SCATTERED-NUMEROUS TSTMS ACROSS REGION WITHIN A WEAK LAPSE
RATE...BUT VERY MOIST ENVIRONMENT WITH PW VALUES OF AROUND TWO
INCHES. WHILE DEEP-LAYER SHEAR WILL REMAIN SUB-OPTIMAL FOR
SUSTAINED ROTATING STORMS...THE MOIST/LOW LCL BOUNDARY LAYER AND
ENHANCED NEAR-GROUND SHEAR INVOF WARM FRONT MAY SUPPORT EPISODIC
LOW-LEVEL STORM ROTATION WITH A RISK FOR A BRIEF TORNADO AND/OR
LOCALLY DAMAGING WIND GUST.

...NY/PA/NJ...

FORCING ASSOCIATED WITH ABOVE-MENTIONED IMPULSE WILL COMBINE WITH
LOW-LEVEL WAA TO FOSTER WIDELY SCATTERED TSTM DEVELOPMENT THIS
AFTERNOON ALONG SRN FRINGE OF DENSE CLOUD SHIELD WHERE ENVIRONMENT
WILL BECOME MARGINALLY UNSTABLE /I.E. MLCAPE OF 250-500 J PER KG/.
ISOLATED OCCURRENCES OF LOCALLY DAMAGING WIND GUSTS AND/OR SEVERE
HAIL WILL BE POSSIBLE INTO THIS EVENING OWING TO THE PRESENCE OF
MODERATELY STRONG DEEP NWLY SHEAR.

..MEAD/ROGERS.. 06/09/2012

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