[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 280601
SWODY1
SPC AC 280559

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1259 AM CDT WED JUN 28 2006

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE GREAT LAKES AND OH
VALLEY AND EWD INTO WRN PARTS OF NY/PA...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ERN CAROLINAS INTO SRN
GA/NRN FL...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF NRN CA/NWRN NV
AND S-CNTRL ORE...

...SYNOPSIS...

FULL LATITUDE TROUGH /ANCHORED BY VORTEX OVER HUDSON BAY/ WILL
ASSUME A SLIGHT NEGATIVE TILT THIS FORECAST PERIOD AS SRN PORTION OF
TROUGH SLOWLY SHIFTS EWD THROUGH THE GREAT LAKES AND OH VALLEY. 
WITHIN THIS PATTERN...SEVERAL WEAKER SHORT WAVE TROUGHS WILL ROTATE
THROUGH THE MEAN TROUGH POSITION...THE MOST NOTABLE OF WHICH ARE
CURRENTLY LOCATED OVER THE MID MS VALLEY...WI AND WRN ONTARIO. IN
THE W...IMPULSE JUST OFF THE SRN CA COAST IS FORECAST TO ROTATE
AROUND PERIPHERY OF UPPER HIGH...AFFECTING PORTIONS OF THE SIERRA
NEVADAS AND WRN GREAT BASIN NEAR THE TIME OF PEAK HEATING.

IN THE LOW-LEVELS...SURFACE LOW INITIALLY OVER THE DELMARVA IS
EXPECTED TO WEAKEN AS IT DEVELOPS NWD INTO THE HUDSON VALLEY WITH
TRAILING FRONTAL BOUNDARY EXTENDING SWD THROUGH THE PIEDMONT OR
COASTAL PLAIN TO THE FL PNHDL. FARTHER W...A WEAK COLD FRONT WILL
PUSH SEWD THROUGH THE WRN/CNTRL GREAT LAKES AND LOWER/MID OH
VALLEY...WHILE WWD EXTENSION OF PRIOR FRONTAL SURGE SLOWLY LIFTS NWD
THROUGH NEB.

...GREAT LAKES/OH VALLEY INTO NRN APPALACHIANS...

CONSIDERABLE UNCERTAINTY EXISTS WITH REGARD TO CONVECTIVE EVOLUTION
OWING TO NUMEROUS IMPULSES ROTATING TROUGH LARGER-SCALE TROUGH AND
THE LACK OF ANY WELL-DEFINED BOUNDARIES TO FOCUS STRONG LOW-LEVEL
CONVERGENCE.  NONETHELESS...RESIDUAL DEWPOINTS IN THE MID/UPPER 50S
TO LOWER 60S COUPLED WITH RELATIVELY COOL MID-LEVEL TEMPERATURES
/-14 TO -16 C AT 500 MB/ WILL CONTRIBUTE TO POCKETS OF MODERATE
INSTABILITY WITH MLCAPES OF 1000-1500 J/KG.

GIVEN THE RELATIVELY WEAK CAP...EXPECT ARCING LINES OR CLUSTERS OF
TSTMS TO BECOMING INCREASINGLY WIDESPREAD BY AFTERNOON FROM THE
GREAT LAKES AND OH VALLEY EWD INTO PORTIONS OF WRN/CNTRL NY/PA. 
WHILE DEEP SHEAR IS NOT FORECAST TO BE PARTICULARLY STRONG /25-35
KTS IN THE LOWEST 6 KM/...THE MODERATELY STRONG LAPSE RATES AND
INSTABILITY SHOULD SUPPORT STORMS CAPABLE OF SEVERE HAIL AND LOCALLY
DAMAGING WINDS THROUGH THE AFTERNOON AND EVENING HOURS.

...NRN CA/NWRN NV/S-CNTRL ORE...

AS MENTIONED ABOVE...SHORT WAVE TROUGH ROTATING AROUND UPPER RIDGE
AXIS WILL BECOME THE FOCUS FOR SCATTERED TO NUMEROUS TSTM
DEVELOPMENT LATER THIS AFTERNOON INTO THIS EVENING.  DAYTIME HEATING
IS EXPECTED TO RESULT IN THE DEVELOPMENT OF RELATIVELY STEEP LAPSE
RATES WITH SBCAPES APPROACHING 500-1500 J/KG.  SOME SEVERE HAIL WILL
BE POSSIBLE WITH THE MORE INTENSE STORMS...HOWEVER IT APPEARS THAT
LOCALLY DAMAGING WINDS WILL BE THE PRIMARY SEVERE WEATHER THREAT
OWING TO RELATIVELY DRY SUB-CLOUD CONDITIONS AND RESULTING DOWNDRAFT
POTENTIAL.

...COASTAL CAROLINAS INTO SRN GA/NRN FL...

RICH BOUNDARY-LAYER MOISTURE /DEWPOINTS OF 70-75 F/ COUPLED WITH
STRONG DIABATIC HEATING WILL CONTRIBUTE TO THE DEVELOPMENT OF A
MODERATELY UNSTABLE AIR MASS AHEAD OF SLOW MOVING FRONT WITH
AFTERNOON MLCAPES INCREASING TO 1500-2500 J/KG.  TSTMS SHOULD BECOME
FAIRLY WIDESPREAD ALONG AND AHEAD OF THIS BOUNDARY BY MID AFTERNOON
INTO EARLY EVENING...INDICATING THE POTENTIAL FOR MERGING COLD POOLS
AND PERHAPS A MORE ORGANIZED DAMAGING WIND THREAT.

...NEB...

KINEMATIC/THERMODYNAMIC ENVIRONMENT WILL BECOME INCREASINGLY
SUPPORTIVE OF SEVERE TSTMS ALONG RETREATING BOUNDARY THIS AFTERNOON
AND EVENING.  PRIMARY UNCERTAINTY IS WHETHER DEEP CONVECTION CAN
DEVELOP AND BECOME SUSTAINED OWING TO THE BUILDING MID-LEVEL HEIGHTS
AS UPPER RIDGE SHIFTS EWD.  SHOULD STORMS DEVELOP...THE THREAT WILL
EXIST FOR LARGE HAIL AND DAMAGING WINDS.  TOO MUCH UNCERTAINTY
PRECLUDES ISSUANCE OF A CATEGORICAL RISK.

..MEAD/JEWELL.. 06/28/2006