[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 191728
SWODY2
SPC AC 191727

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1227 PM CDT WED JUL 19 2006

VALID 201200Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MIDDLE MS VALLEY
ACROSS THE GREAT LAKES REGION...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN HIGH PLAINS INTO
THE CENTRAL PLAINS...

...SYNOPSIS...
UPPER FLOW PATTERN IS FORECAST TO AMPLIFY TOMORROW AS LEAD SHORT
WAVE TROUGH CURRENTLY ACROSS THE SRN CANADIAN PRAIRIE PROVINCES/FAR
NRN PLAINS PROGRESSES EWD ACROSS ERN CANADA...WHILE UPSTREAM SHORT
WAVE TROUGH NEARING THE BRITISH COLUMBIA COAST IS PREDICTED TO DIG
SEWD OVER THE NRN PLAINS IN RESPONSE TO BUILDING RIDGE OVER THE NRN
INTERMOUNTAIN REGION.  SURFACE COLD FRONT IS EXPECTED TO MOVE
EWD/SEWD ACROSS THE GREAT LAKES AND CENTRAL PLAINS...REACHING A SERN
QUEBEC/WRN PA/SRN INDIANA/SRN KS LINE BY THE END OF THE PERIOD.

...GREAT LAKES/OH VALLEY REGION...
A BAND OF STRONG/LOCALLY SEVERE CONVECTION ALONG/AHEAD OF THE COLD
FRONT MAY BE OCCURRING EARLY IN THE PERIOD FROM LAKE HURON/LOWER MI
SWWD INTO NRN/CENTRAL IL AS DAY 1 OVERNIGHT MCS CONTINUES INTO THE
DAY 2 PERIOD.  AMPLE LOW LEVEL MOISTURE WITH SURFACE DEW POINTS
GENERALLY IN THE UPPER 60S/LOWER 70S (LOCALLY MID/UPPER 70S OVER THE
MIDDLE MS VALLEY) WILL BE PRESENT AHEAD OF THE FRONT AND/OR ANY
EFFECTIVE OUTFLOW BOUNDARIES.  PLUME OF STEEPER MID LEVEL LAPSE
RATES WILL EXTEND FROM THE MIDDLE MS VALLEY ENEWD INTO THE LOWER
GREAT LAKES IN ADVANCE OF CONVECTIVE ACTIVITY. THIS WILL ENHANCE
INSTABILITY IN REGIONS WHERE LIMITED CLOUD COVER AND STRONGER
DIURNAL HEATING OCCUR...WITH AFTERNOON MLCAPE RANGING FROM 1000-1500
J/KG FROM THE ST LAWRENCE VALLEY INTO THE UPPER OH VALLEY TO
2500-4000 J/KG ACROSS THE MIDDLE MS VALLEY.

PRIMARY MID/UPPER LEVEL JET WILL CURVE CYCLONICALLY FROM THE UPPER
GREAT LAKES INTO THE ST LAWRENCE VALLEY...WITH A SECONDARY JET
STREAM ARCING ANTI-CYCLONICALLY FROM THE UPPER MS VALLEY ACROSS THE
LOWER OH/TN VALLEYS.  THIS DIFFLUENT JET PATTERN WILL ENHANCE UPPER
LEVEL DIVERGENCE ACROSS THE LOWER GREAT LAKES INTO THE OH VALLEY
WITH RESULTANT INCREASE IN LARGE SCALE ASCENT ABOVE THE LOW LEVEL
FRONTAL ZONE. THIS SHOULD SUPPORT ADDITIONAL BANDS OF THUNDERSTORMS
BEGINNING IN THE AFTERNOON...WITH ACTIVITY SPREADING EWD/SEWD AHEAD
OF THE FRONT.  DEEP LAYER VERTICAL SHEAR OF 30-40 KT FROM THE LOWER
LAKES INTO THE ST LAWRENCE VALLEY WILL SUPPORT ORGANIZED SEVERE
CONVECTION /INCLUDING POSSIBILITY OF ISOLATED SUPERCELLS/ WITH
PRIMARY THREAT FOR DAMAGING WIND GUSTS AND LARGE HAIL WITH STRONGER
CELLS. THIS ACTIVITY IS LIKELY TO REMAIN ORGANIZED AND PERSIST
THROUGH THE OVERNIGHT HOURS EVENTUALLY REACHING UPSTATE NY/NRN VT
AFTER 06Z.

ALTHOUGH VERTICAL SHEAR IS FORECAST TO BE WEAKER /20-30 KT IN THE
LOWEST 6 KM/ FARTHER SOUTHWEST ACROSS THE MIDDLE MS/LOWER OH
VALLEYS...LARGER VALUES OF MLCAPE WILL BE SUPPORTIVE OF SEVERE
STORMS. WEAKER DYNAMIC FORCING OVER THIS REGION SUGGESTS STORMS WILL
GRADUALLY DECREASE IN COVERAGE AND INTENSITY DURING THE 03-06Z
PERIOD.

...NRN HIGH PLAINS INTO CENTRAL PLAINS...
LOW LEVEL UPSLOPE FLOW IS FORECAST TO DEVELOP OVER THE CENTRAL/NRN
HIGH PLAINS NORTH OF THE SURFACE FRONT...WHICH WILL RESULT IN AN
AXIS OF HIGHER DEW POINTS SPREADING FROM NRN KS/SRN NEB NWWD INTO
ERN PARTS OF WY/MT AND THE WRN PARTS OF THE DAKOTAS AND NEB.  A
STEEP LAPSE RATE ENVIRONMENT COUPLED WITH INCREASING LOW LEVEL
MOISTURE WILL RESULT IN UNSTABLE CONDITIONS WITH MUCAPE RANGING FROM
OF 1000-1500 J/KG OVER THE HIGH PLAINS TO 2000-3000 J/KG OVER SRN
NEB/NRN KS.  THUNDERSTORMS ARE EXPECTED TO INCREASE/INTENSIFY DURING
THE AFTERNOON OVER THE NRN HIGH PLAINS AS THE NEXT SHORT WAVE TROUGH
DIGS SEWD FROM MT TOWARD THE NRN/CENTRAL PLAINS.  FORECAST SOUNDINGS
EXHIBIT PRONOUNCED DIRECTIONAL/SPEED SHEAR WITH HEIGHT AS LOW LEVEL
SELY WINDS VEER TO WESTERLY IN THE MIDDLE LEVELS...PROVIDING A
FAVORABLE ENVIRONMENT FOR SEVERE STORMS INCLUDING A FEW SUPERCELLS. 
LARGE HAIL...DAMAGING WINDS...AND ISOLATED TORNADOES WILL BE
POSSIBLE WITH STRONGER CELLS DURING THE AFTERNOON AND EVENING. THE
CONVECTION IS EXPECTED TO CONSOLIDATE INTO ONE OR MORE MCS/S FROM
THE LATE EVENING THROUGH THE OVERNIGHT HOURS AS IT SPREADS SEWD INTO
PARTS OF NEB AND POSSIBLY FAR NRN KS WHERE ELEVATED
MOISTURE/INSTABILITY WILL BE PRESENT NORTH OF THE SURFACE FRONT. 
PRIMARY SEVERE THREAT IS EXPECTED TO GRADUALLY TRANSITION TO LARGE
HAIL AND ISOLATED WIND DAMAGE AS LOW LEVEL WARM
ADVECTION/CONVERGENCE ALONG AND NORTH OF THE FRONT STRENGTHENS IN
RESPONSE TO THE DEVELOPING NOCTURNAL LOW LEVEL JET OVER THE PLAINS.

...LOWER MS VALLEY/GULF COAST...
FORECAST SOUNDINGS ACROSS THIS REGION INDICATE VERY WARM/MOIST LOW
LEVEL AIR MASS WILL PERSIST TOMORROW...WITH A STRONG DECREASE IN
THETA-E PREDICTED ABOVE 850 MB.  THE PRESENCE OF DRIER AIR ALOFT
COUPLED WITH ANTICIPATED DEVELOPMENT OF STEEP LAPSE RATES IN THE
LOWEST 1-2 KM SUGGEST POTENTIAL FOR A FEW WET MICROBURSTS TO DEVELOP
DURING THE AFTERNOON AND EVENING.  NELY MID LEVEL WINDS OF 15-25 KT
MAY ALLOW MARGINALLY ORGANIZED CONVECTION TO PERSIST ACROSS THIS
REGION...BUT OVERALL COVERAGE IS NOT EXPECTED TO WARRANT A SLIGHT
RISK ATTM.

...AZ/EXTREME SERN CA...
SYNOPTIC PATTERN THAT IS DOMINATED BY UPPER RIDGE FROM THE GREAT
BASIN EWD INTO THE PLAINS WILL CONFINE STRONGER ELY COMPONENT OF THE
DEEP LAYER FLOW ACROSS SRN PART OF AZ. PRESENCE OF A DEEP
SURFACE-BASED WELL-MIXED LAYER AND SUFFICIENT MOISTURE WILL ALLOW
THUNDERSTORMS TO DEVELOP OVER PARTS OF THE RIM AND MOUNTAINS OF EAST
CENTRAL/SERN AZ...WITH ACTIVITY PROPAGATING PRIMARILY WWD ACROSS THE
LOWER DESERTS TOWARD THE LOWER CO RIVER VALLEY.  ALTHOUGH THERE IS
TYPICAL UNCERTAINTY IN THE DETAILS OF CONVECTIVE EVOLUTION ACROSS
THIS AREA...POTENTIAL WILL EXIST FOR A FEW WET MICROBURSTS TO
DEVELOP.

..WEISS.. 07/19/2006