[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 171721
SWODY2
SPC AC 171720

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT MON JUL 17 2006

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NEW ENGLAND INTO THE OH
VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE NRN PLAINS...

...SYNOPSIS...
STRONGER WESTERLY FLOW ALOFT WILL REMAIN ALONG THE NRN TIER OF
STATES AS TWO SHORT WAVE TROUGHS PROGRESS EWD ACROSS THE CANADIAN/US
BORDER.  LEAD SHORT WAVE CURRENTLY APPROACHING THE UPPER GREAT LAKES
WILL MOVE FROM WRN QUEBEC AND THE LOWER GREAT LAKES EWD ACROSS THE
ST LAWRENCE VALLEY/NRN NEW ENGLAND TOMORROW...AS UPSTREAM TROUGH
MOVES ACROSS THE SRN CANADIAN PRAIRIE PROVINCES.  FARTHER
SOUTH...LOW LATITUDE TROUGH IN THE SUBTROPICAL EASTERLIES WILL
CONTINUE WWD INTO THE PACIFIC OFF NRN BAJA AS INVERTED TROUGH MOVE
NWWD ACROSS CENTRAL/SRN CA.

AT THE SURFACE...A COLD FRONT WILL MOVE SEWD ACROSS NEW ENGLAND AND
THE OH VALLEY. THE WRN PART OF THE FRONT WILL BEGIN TO LIFT NWD
DURING THE EVENING AS A LOW CENTER DEVELOPS EWD INTO NRN NEB/SRN
SD...AND A SECOND COLD FRONT MOVES SEWD ACROSS THE DAKOTAS.

...NERN STATES/OH VALLEY...
AMPLE LOW LEVEL MOISTURE WITH SURFACE DEW POINTS IN THE UPPER
60S/LOWER 70S WILL BE PRESENT AHEAD OF THE ADVANCING COLD
FRONT...BENEATH AN ELEVATED MIXED LAYER PLUME EXTENDING EWD FROM THE
PLAINS INTO PARTS OF NEW ENGLAND.  THE STEEP MID LEVEL LAPSE RATES
ABOVE THE LOW LEVEL MOISTURE LAYER WILL CONTRIBUTE TO MODERATE
INSTABILITY WITH MLCAPE OF 1500-2500 J/KG AND PROVIDE A VERY
FAVORABLE THERMODYNAMIC ENVIRONMENT FOR STRONG/SEVERE THUNDERSTORM
DEVELOPMENT.

A BAND OF THUNDERSTORMS IS EXPECTED TO BE ONGOING IN THE MORNING
ALONG THE COLD FRONT FROM THE LOWER GREAT LAKES NEWD INTO NRN NEW
ENGLAND.  THE CAPPING INVERSION ASSOCIATED WITH THE EML IN SRN NEW
ENGLAND IS EXPECTED TO INHIBIT CONVECTIVE INITIATION IN THE WARM
SECTOR SOUTH OF THE FRONT DURING THE MORNING.  STORMS
ALONG/IMMEDIATELY AHEAD OF THE FRONT ARE LIKELY TO INTENSIFY BY
MID/LATE MORNING AS STRONG INSOLATION DESTABILIZES THE
PRE-CONVECTIVE ENVIRONMENT...AND DYNAMIC FORCING FOR LARGE SCALE
ASCENT INCREASES WITHIN RIGHT ENTRANCE REGION OF THE UPPER LEVEL JET
MOVING ACROSS THE ST LAWRENCE VALLEY.  ALTHOUGH THE STRONGEST
VERTICAL SHEAR WILL BE LOCATED PRIMARILY NORTH OF THE COLD
FRONT...DEEP LAYER SHEAR OF 25-35 KT WILL BE SUFFICIENT TO ENHANCE
CONVECTIVE ORGANIZATION WITH POTENTIAL FOR A FEW SUPERCELLS TO
DEVELOP...ESPECIALLY OVER PARTS OF NEW ENGLAND/SERN NY INTO NRN PA. 
UNIDIRECTIONAL WIND PROFILES ABOVE THE PBL SUGGEST PRIMARY
CONVECTIVE MODE WILL BE IN THE FORM OF LINE SEGMENTS INCLUDING
EMBEDDED BOW ECHOES GIVEN THE DRY AIR WITHIN THE ELEVATED MIXED
LAYER AND ENHANCED POTENTIAL FOR STRONG DOWNDRAFTS.  ALTHOUGH
VERTICAL SHEAR DECREASES WITH WWD EXTENT ACROSS THE OH
VALLEY...SUFFICIENT INSTABILITY/DRY AIR ALOFT SUGGESTS POTENTIAL FOR
A FEW SEVERE STORMS INTO PARTS OF THE OH VALLEY.  SEVERE THREAT IS
EXPECTED TO DIMINISH BY 03-06Z.

...NRN PLAINS INTO UPPER MS VALLEY...
THE ELEVATED MIXED LAYER WILL PERSIST FROM THE ROCKIES INTO THE NRN
PLAINS TOMORROW...EFFECTIVELY CAPPING DEVELOPMENT OF SURFACE-BASED
CONVECTION THROUGH MOST OF THE PERIOD. AS THE WARM FRONT LIFTS NWD
ACROSS THE LOWER/MIDDLE MO RIVER VALLEY DURING THE LATE AFTERNOON
INTO THE OVERNIGHT HOURS...MOISTURE WILL RETURN NWD INTO IA/ERN
NEB/CENTRAL AND ERN SD/SRN MN BENEATH THE EML. ALTHOUGH THERE IS
POTENTIAL FOR ISOLATED HIGH-BASED THUNDERSTORMS TO DEVELOP EWD
ACROSS THE NRN HIGH PLAINS DURING THE LATE AFTERNOON AND EVENING
WITH AN ATTENDANT THREAT FOR LOCAL MICROBURSTS...THE PRIMARY
ELEVATED CONVECTIVE DEVELOPMENT IS EXPECTED DURING THE OVERNIGHT
HOURS AS WARM ADVECTION LIFT INCREASES NORTH OF THE WARM FRONT AS
THE NOCTURNAL LOW LEVEL JET INTENSIFIES.  VERTICAL WIND PROFILES ARE
FORECAST TO EXHIBIT PRONOUNCED VEERING WITH HEIGHT AS A STRONG MID
LEVEL JET STREAK ASSOCIATED WITH THE NEXT SHORT WAVE TROUGH MOVES
EWD ACROSS THE NRN PLAINS.  THIS WILL PROVIDE SUFFICIENT SHEAR TO
SUPPORT ISOLATED ELEVATED SUPERCELLS AFTER 03-06Z...WITH STRONGER
CELLS CAPABLE OF PRODUCING LARGE HAIL.

..WEISS.. 07/17/2006