SWODY2
SPC AC 111731
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1231 PM CDT FRI MAY 11 2007
VALID 121200Z - 131200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN
ROCKIES/PLAINS...
..SYNOPSIS...
PRIMARY BELT OF WESTERLIES WILL REMAIN ACROSS THE NRN TIER OF THE
CONTINENTAL U.S. THROUGH SATURDAY...AS STRONG UPPER RIDGE BUILDS EWD
FROM THE ROCKIES TO THE PLAINS STATES REACHING THE LOWER MO TO LOWER
TN RIVER VALLEYS BY 12Z SUNDAY.
..NRN ROCKIES/HIGH PLAINS...
A PACIFIC TROUGH NOW CENTERED AT 40N 133W PER WATER VAPOR IMAGERY IS
FORECAST TO MOVE INLAND OVER THE PACIFIC NW DURING DAY 2...WITH A
LEAD SHORT WAVE TROUGH...CURRENTLY LOCATED OFF THE NRN CA COAST...
PRECEDING THE LARGER TROUGH INLAND. THIS LEAD TROUGH IS EXPECTED TO
MOVE ENEWD ACROSS THE NRN ROCKIES/HIGH PLAINS AND SHOULD REACH ND/
CANADIAN BORDER REGION BY LATE DAY 2.
A SELY LOW LEVEL WIND SHOULD REMAIN PERSISTENT ACROSS THE NRN HIGH
PLAINS ON SATURDAY IN RESPONSE TO HEIGHT FALLS AS THE LEAD MID LEVEL
IMPULSE RESULTS IN WEAK HEIGHT FALLS AND THE UPPER RIDGE BEGINS TO
SHIFT EWD INTO THE PLAINS. ALTHOUGH THERE WILL BE SOME INCREASE OF
SURFACE DEWPOINTS INTO THE LOWER 50S ACROSS ERN MT...A CONTINUED
STREAM OF MID LEVEL MOISTURE WITHIN SWLY FLOW ALOFT IS EXPECTED TO
MAINTAIN SUFFICIENT ZONE OF PRECIPITABLE WATER VALUES FOR THE
LIKELIHOOD OF DEEP CONVECTION. THIS COMBINED WITH SURFACE HEATING
AND STEEP LAPSE RATES WILL RESULT IN MODERATE INSTABILITY OVER MUCH
OF MT.
LOW LEVEL CONVERGENCE WITHIN BAROCLINIC ZONE EXPECTED TO EXTEND FROM
CENTRAL ID TO NORTH CENTRAL MT COMBINED WITH ASCENT AHEAD OF LEAD
IMPULSE SPREADING ENEWD OVER THE NRN ROCKIES DURING PEAK HEATING ARE
EXPECTED TO RESULT IN TSTM DEVELOPMENT SATURDAY AFTERNOON IN THE
HIGHER TERRAIN. STRONG DEEP LAYER SHEAR AND MODERATE INSTABILITY
WILL SUPPORT ORGANIZED STORMS WITH SUPERCELLS POSSIBLE RESULTING IN
THE THREAT FOR HAIL GIVEN STEEP LAPSE RATE ENVIRONMENT. INVERTED-V
THERMODYNAMIC PROFILES ALSO INDICATE LIKELIHOOD FOR DAMAGING WIND
GUSTS. ANY STORMS THAT CAN MOVE OFF THE HIGHER TERRAIN ONTO THE
ADJACENT PLAINS OF MT WILL ALSO HAVE A THREAT FOR SEVERE WEATHER AS
THEY MOVE EWD INTO SELY INFLOW OF GREATER MOISTURE/INSTABILITY.
DEEP LAYER SHEAR WILL SUPPORT EWD EXTENT FOR ORGANIZED STORMS AS
ACTIVITY SPREADS E TOWARD ERN MT/DAKOTAS AFTER 13/00Z.
..SD/MID MO VALLEY...
A SURFACE BOUNDARY IS EXPECTED TO REMAIN STATIONARY DURING MOST OF
DAY 2 PERIOD FROM SRN SD AND THEN SEWD TO THE LOWER MO RIVER VALLEY
BEFORE MOVING NWD TO THE SD/ND BORDER AS SURFACE LOW MOVES EWD INTO
WRN DAKOTAS SATURDAY NIGHT. DESPITE STRONG SURFACE HEATING...AN
ELEVATED MIXED LAYER SPREADING EWD ACROSS THE PLAINS AS UPPER RIDGE
BUILDS E ON SATURDAY IS EXPECTED TO RESULT IN A STRONG CAP AND
LIKELY PRECLUDE AFTERNOON TSTM DEVELOPMENT. IF A STORM CAN DEVELOP
IN THIS ENVIRONMENT...THE MAGNITUDE OF DEEP LAYER SHEAR ALONG SRN
EXTENT OF STRONGER WNWLY MID LEVEL FLOW AND MODERATE INSTABILITY
WOULD SUPPORT A SUPERCELL AND SEVERE THREAT.
HOWEVER...AT THIS TIME...MODELS SUGGEST GREATER POTENTIAL FOR
ELEVATED TSTM DEVELOPMENT AND ISOLATED SEVERE STORMS SATURDAY NIGHT
ACROSS THE DAKOTAS INTO MN AS NOCTURNAL SLY LLJ STRENGTHENS AND
VEERS OVERNIGHT.
..MID ATLANTIC...
SHORT WAVE TROUGH...CURRENTLY LOCATED ALONG ND/CANADIAN BORDER... IS
EXPECTED TO DIG SEWD FROM THE GREAT LAKES TO THE MID ATLANTIC COAST
ON SATURDAY AS UPPER TROUGH AMPLIFIES OVER THE NERN STATES.
THIS WILL SUPPORT STRENGTHENING MID/UPPER LEVEL FLOW ACROSS THE OH
VALLEY TO MID ATLANTIC REGION. ALTHOUGH DEEP LAYER SHEAR WILL BE
STRONG ENOUGH FOR ORGANIZED STORMS ACROSS MUCH OF VA TO
DELMARVA...NRN EXTENT OF HIGHER MOISTURE VALUES/INSTABILITY REMAINS
UNCERTAIN. IN ADDITION...WEAK LAPSE RATES SHOULD TEND TO LIMIT
DEVELOPMENT OF STRONGER INSTABILITY AND POTENTIAL FOR MORE ROBUST
UPDRAFTS. A WEAKER MID LEVEL IMPULSE...NOW LOCATED ALONG MO/IA
BORDER...SHOULD PROVIDE SUFFICIENT ASCENT FOR TSTM DEVELOPMENT
SATURDAY AFTERNOON AS IT APPROACHES THE CENTRAL APPALACHIANS.
THUS...GIVEN AT LEAST WEAK INSTABILITY AND STRONG DEEP LAYER
SHEAR...THIS OUTLOOK WILL MAINTAIN LOW SEVERE PROBABILITIES.
..CAROLINAS WSWWD TO LOWER MS VALLEY AND INTO FL...
WEAK ZONE OF LOW LEVEL CONFLUENCE MOVING SWD THROUGH THIS REGION
WILL BE A FOCUS FOR TSTM DEVELOPMENT AGAIN ON SATURDAY AS WEAKENING
UPPER TROUGH TRANSLATES SWD INTO THE GULF BASIN. MOIST AIR MASS
WILL AID IN THE TSTM FORMATION...BUT WEAK LAPSE RATES AND WEAK DEEP
LAYER SHEAR SHOULD PRECLUDE POTENTIAL FOR STORM ORGANIZATION. A
LARGE AREA OF LOW SEVERE PROBABILITIES WILL BE MAINTAINED ACROSS
THIS REGION DUE TO POTENTIAL FOR ISOLATED SEVERE PULSE-TYPE STORMS.
ISOLATED THREAT FOR SEVERE STORMS ACROSS FL SHOULD BE CONFINED TO
THE ERN PENINSULA WHERE ERN SEA BREEZE WILL LIKELY BE THE PRIMARY
FOCUS FOR LOW LEVEL CONVERGENCE.
.PETERS.. 05/11/2007
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