[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 180605
SWODY1
SPC AC 180603

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0103 AM CDT TUE JUL 18 2006

VALID 181200Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NERN STATES WWD INTO
THE OH VLY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN SD INTO WRN MN...

...SYNOPSIS...
PRIMARY WLYS WILL REMAIN ALONG THE CANADIAN BORDER THROUGH TUE.  TWO
SHORTWAVE TROUGHS WILL MOVE EWD WITHIN THE FLOW.  THE LEAD TROUGH...
CURRENTLY MOVING ACROSS THE GRTLKS REGION WILL MOVE ACROSS QUE AND
ACROSS THE ST. LAWRENCE VLY AND NRN NEW ENGLAND TUE AFTN.  THE
UPSTREAM IMPULSE WILL MOVE ACROSS THE SRN CANADIAN PRAIRIES.

IN THE LWR LVLS...A COLD FRONT WILL MOVE SEWD ACROSS NEW ENGLAND AND
THE OH VLY.  WRN END OF THE FRONT WILL BEGIN TO LIFT NWD DURING TUE
NIGHT AS A LOW DEVELOPS EWD FROM THE HIGH PLAINS INTO PARTS OF THE
DAKS.  MEANWHILE...A SECONDARY COLD FRONT WILL BEGIN TO SWING EWD
INTO THE DAKS BY LATE TUE AFTN.

...NERN STATES/MID-UPPER OH VLY...
A MOIST BOUNDARY LAYER...CHARACTERIZED BY DEW POINTS IN THE UPPER
60S TO LOWER 70S...WILL REMAIN IN PLACE ALONG/SOUTH OF THE COLD
FRONT ON TUE.  ATOP THIS MOISTURE...A PLUME OF STEEP H7-H5 LAPSE
RATES OF 7-7.5 DEG C PER KM EMANATING FROM THE PLAINS WILL EXIST. 
THIS ELEVATED MIXED LAYER WILL LIKELY DELAY CONVECTIVE INITIATION
UNTIL AFTN.  BUT...COMBINATION OF STRONG HEATING...WEAK HEIGHT FALLS
AND CONVERGENCE ALONG THE COLD FRONT/PRE-FRONTAL TROUGHS...CINH
SHOULD ERODE SUFFICIENTLY FOR TSTMS INITIATION FROM ME SWWD INTO NRN
OH BY MID-AFTN.

THE STRONGER DEEP LAYER SHEAR WILL EXIST ALONG THE BASE OF THE H5
TROUGH ACROSS NY EWD INTO NEW ENGLAND WHERE 40-50 KTS OF FLOW SHOULD
BE COMMON.  WLY UNIDIRECTIONAL NATURE TO THE FLOW WILL BE SUFFICIENT
FOR SUPERCELLS...BUT EVOLUTION INTO BOWING LINE SEGMENTS WILL LIKELY
OCCUR QUICKLY...GIVING DAMAGING WIND GUSTS ALONG WITH LARGE HAIL. 
THERE ARE SOME UNCERTAINTIES REVOLVING AROUND FRONTAL TIMING AND
ANTICIPATED COVERAGE OF THE STORMS.  ONCE MORE CONFIDENCE IS
GAINED...AN UPGRADE TO CATEGORICAL MODERATE RISK MAY BE NEEDED.

FARTHER SW...VERTICAL SHEAR WILL BE MUCH WEAKER...BUT MAGNITUDE OF
LAPSE RATES/HOT BOUNDARY LAYER WILL BE FAVORABLE FOR MICROBURSTS AND
PERHAPS AN ISOLD SUPERCELL OR TWO WITH LARGE HAIL FROM PARTS OF PA
WWD INTO OH.

...LWR OH VLY...
REGION WILL REMAIN BENEATH DIFFLUENT UPPER FLOW REGIME THROUGH TUE. 
VERY UNSTABLE CONDITIONS WILL DEVELOP ACROSS THE LWR OH VLY OWING TO
RICH BOUNDARY LAYER MOISTURE AND STEEP MID-LEVEL LAPSE RATES. 
REMNANT OUTFLOW BOUNDARIES/COLD FRONT WILL BE MOVING SWD THROUGH
PARTS OF IND WWD INTO PARTS OF MO AND COULD BE IMPETUS FOR TSTMS BY
LATE AFTN.  MAIN LIMITING FACTORS FOR STORMS WILL BE THE WARM
TEMPERATURES ALOFT.  HOWEVER...GIVEN A STORM...LARGE HAIL AND
DAMAGING WINDS WILL BE LIKELY.

...GULF COASTAL REGION...
UPPER SHEAR AXIS WILL REMAIN ACROSS THE GULF COASTAL REGION ON TUE
AND TSTMS SHOULD FORM IN ASSOCIATION WITH THIS FEATURE AGAIN TUE
AFTN.  SATL SHOWS A CONSIDERABLE AMOUNT OF DRY AIR ENTRAINING INTO
THIS FEATURE ATOP RICH BOUNDARY LAYER MOISTURE.  THIS SUGGESTS THAT
ISOLD MICROBURSTS MAY OCCUR WITH THE STRONGER STORMS ANYWHERE ALONG
THE GULF COAST.

...FOUR CORNERS REGION...
TSTMS WILL LIKELY FORM BENEATH UPPER RIDGE AXIS...WITH HIGHEST
PROBABILITIES ACROSS THE FOUR CORNERS REGION.  TROPOSPHERIC FLOW
WILL BE LIGHT AND PULSE MULTICELL CLUSTERS WILL BE THE MAIN
CONVECTIVE MODE.  TYPICALLY DRY SUB-CLOUD LAYER COULD CONTRIBUTE TO
ISOLD STORMS PRODUCING DAMAGING WIND GUSTS.

...NRN PLAINS...
A STRONG EML WILL CONTINUE FROM THE ROCKIES INTO THE PLAINS TUE. 
THIS SHOULD EFFECTIVELY CAP SFC BASED PARCELS. BUT...HIGH BASED
CONVECTION IS APT TO INCREASE OFF THE HIGHER TERRAIN. AS THE WARM
FRONT LIFTS NWD ACROSS THE LWR/MIDDLE MO RVR VLY DURING LATE
AFTN/OVERNIGHT...MOISTURE ADVECTION WILL INCREASE ALONG AN
ACCELERATING SLY LLJ BENEATH THE EML.  AS A RESULT...SOME OF THE
AFTN CONVECTION MAY EVOLVE INTO AN MCS OVERNIGHT ACROSS PARTS OF SD
INTO MN...OR ALONG THE EDGE OF THE STRONGER CAP.  EFFECTIVE SHEAR
WILL BE INCREASING OVERNIGHT AND GIVEN MAGNITUDE OF LAPSE
RATES/ELEVATED CAPE...A FEW STORMS MAY PRODUCE LARGE HAIL AND
PERHAPS GUSTY WINDS.

..RACY/JEWELL.. 07/18/2006