[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 181240
SWODY1
SPC AC 181238

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0738 AM CDT TUE JUL 18 2006

VALID 181300Z - 191200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NEW ENGLAND SWWD ACROSS
THE OHIO VALLEY...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE NRN
PLAINS...

...SYNOPSIS...
LARGE UPPER RIDGE WILL DOMINATE THE WEATHER ACROSS MOST OF THE
CONUS...WITH THE STRONGER MID LEVEL WINDS RESTRICTED TO THE NRN
BORDER STATES. WITHIN THESE WESTERLIES...ONE SHORTWAVE TROUGH WILL
MOVE FROM THE GREAT LAKES INTO NEW ENGLAND...WHILE A SECOND SYSTEM
MOVES FROM OREGON INTO THE NRN ROCKIES. IN ASSOCIATION WITH THE LEAD
TROUGH...A COLD FRONT WILL MOVE SEWD ACROSS NEW ENGLAND/OH VALLEY
AND REMAIN QUASI-STATIONARY ACROSS THE MID MS VALLEY. THE WRN END OF
THE FRONT WILL LIFT NWD FROM KS INTO NEB TONIGHT AS AN AREA OF LOW
PRESSURE DEVELOPS ACROSS THE NRN PLAINS.

...NEW ENGLAND AND NY...
ALTHOUGH ELEVATED STORMS ARE NOW MOVING THROUGH WRN ME... RELATIVELY
WARM TEMPERATURES ALOFT ARE LIKELY TO INHIBIT SURFACE BASED
CONVECTIVE DEVELOPMENT UNTIL LATE MORNING/EARLY AFTERNOON. THIS
MEANS STRONGER CONVECTION IS MORE LIKELY LATER TODAY FROM CENTRAL ME
SWWD INTO LOWER NY. ONCE SURFACE BASED STORMS DEVELOP ...THEY WILL
BE ABLE TO INGEST STRONG INSTABILITY WITH MLCAPES FROM 2000-3000
J/KG. THIS INSTABILITY AND 40-50 KT DEEP LAYER SHEAR WILL SUPPORT
SUPERCELLS. HOWEVER...THE DEEP UNDIRECTIONAL WLY WINDS THROUGHOUT
THE TROPOSPHERE ARE LIKELY TO EVOLVE STORMS INTO LINES/BOWS...WITH
WIND DAMAGE THE PRIMARY THREAT. ALTHOUGH UNCERTAINTY EXISTS ON
WHEN/WHERE STORMS ARE MOST FAVORED...A HIGHER WIND POTENTIAL IS
EXPECTED ACROSS THE ERN PORTIONS OF NEW ENGLAND SINCE THE
FRONT/STORMS SHOULD PUSH THROUGH THESE AREAS DURING THE TIME OF MAX
HEATING/INSTABILITY. THE SEVERE THREAT SHOULD END BY MID EVENING AS
THE STORMS MOVE OFFSHORE.

...PA/OH AND MID MS VALLEYS...
COLD FRONT/OUTFLOW BOUNDARY EXTEND FROM WRN NY TO A WEAK WAVE
LOCATED IN NORTH CENTRAL IL...AND THEN SWWD INTO NRN MO. ELEVATED
CONVECTION HAD DEVELOPED OVER CENTRAL IL THIS MORNING WITHIN
INSTABILITY AXIS AND ZONE OF WEAK WARM ADVECTION...BUT STORMS SHOULD
WEAKEN THIS MORNING AS WARM ADVECTION CEASES. MORE INTENSE
CONVECTION IS EXPECTED TO DEVELOP THIS AFTERNOON ALONG THE WEAK COLD
FRONT/REMNANT OUTFLOW BOUNDARIES. STRONG DAYTIME HEATING... STEEP
MID LEVEL LAPSE RATES AND A MOIST BOUNDARY LAYER WILL RESULT IN
MLCAPES TO RANGE FROM 2000 J/KG OVER PA/OH TO NEARLY 4000 J/KG
ACROSS SRN IL/EAST CENTRAL MO. WARM MID LEVEL TEMPERATURES SHOULD
LIMIT WRN EXTENT OF CONVECTIVE DEVELOPMENT TO ERN MO/IL...BUT MOST
INTENSE CONVECTION SHOULD BE LOCATED ON THE ERN EDGE OF THIS CAP.
ONCE STORMS DEVELOP...THE AMOUNT OF INSTABILITY AND 25-30 KT DEEP
LAYER SHEAR WILL FAVOR MULTICELL STORM CLUSTERS WITH HAIL AND WIND
DAMAGE.

...NRN PLAINS...
TIMING AND LOCATION OF SEVERE CONVECTION IS QUESTIONABLE DUE TO
SUBTLE DIFFERENCES IN THE CURRENT AND PAST ETA/GFS MODEL RUNS.
HOWEVER...MODELS GENERALLY SUPPORT A LOW LEVEL JET/WARM ADVECTION
DEVELOPING OVERNIGHT ACROSS THE ERN DAKOTAS/WRN MN AS A SHORTWAVE
TROUGH MOVES INTO THE NRN ROCKIES. THE BOUNDARY LAYER WILL BE
STRONGLY CAPPED...BUT STEEP LAPSE RATES ABOVE THE INVERSION WILL BE
FAVORABLE FOR ELEVATED CONVECTION TO DEVELOP AFTER 03-06Z.
EFFECTIVE SHEAR WILL BE INCREASING OVERNIGHT AND THE STEEP LAPSE
RATES/ELEVATED CAPE MAY SUPPORT STORMS WITH SEVERE HAIL.

...GULF COASTAL REGION...
NUMEROUS THUNDERSTORMS WERE LOCATED OFF THE LA COAST THIS MORNING IN
ASSOCIATION WITH A WEAK SHEAR AXIS ALOFT. STORMS SHOULD DEVELOP
INLAND LATER THIS MORNING AND AFTERNOON AND ALTHOUGH THE DEEP LAYER
SHEAR IS WEAK...STRONG INSTABILITY AND HOT TEMPERATURES WILL SUPPORT
SHORT-LIVED MICRO BURSTS.

...FOUR CORNERS REGION...
MID/HIGH LEVEL MOISTURE TRAPPED UNDER UPPER RIDGE WILL LIKELY RESULT
IN NUMEROUS DIURNAL THUNDERSTORMS. ENVIRONMENTAL WINDS/ SHEAR WILL
BE WEAK...BUT A RELATIVELY DRY AND DEEP BOUNDARY LAYER MAY SUPPORT A
FEW STRONG WINDS GUSTS.

..IMY/JEWELL.. 07/18/2006