[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 281630
SWODY1
SPC AC 281628

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT FRI JUL 28 2006

VALID 281630Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE MID
ATLANTIC INTO THE SRN NEW ENGLAND...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A PART OF THE NRN PLAINS
INTO THE NRN GREAT LAKES...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF AZ...

...MID ATLANTIC INTO SRN NEW ENGLAND...
ACTIVE DAY FOR THUNDERSTORMS EXPECTED ACROSS THIS REGION AS SLOW
MOVING MID LEVEL TROUGH AND ACCOMPANYING 40+ KT MID LEVEL JET /30+
KT WSWLY LLJ/ OVERSPREAD THE NORTHEAST.  AIR MASS REMAINS QUITE
MOIST WITH SURFACE DEW POINTS WELL INTO THE 70S AHEAD OF THIS
FEATURE...WHICH WILL SUPPORT A VERY WARM/HUMID WARM SECTOR AS
AFTERNOON HIGHS REACH INTO AT LEAST THE UPPER 80S/LOWER 90S. 
DESPITE LARGE LOW LEVEL THETA-E VALUES IN PLACE...WEAK LAPSE RATES /
H7 TO H5 LAPSE RATES AOB 6 C KM-1 / WILL LIMIT AVAILABLE CAPE. 
REGARDLESS...MLCAPE SHOULD EXCEED 2000 J/KG ACROSS THE MID ATLANTIC
AND 1500 J/KG INTO SRN NEW ENGLAND BY THE MID AFTERNOON.  DEEP LAYER
SHEAR FROM 30-40 KT WILL BE SUPPORTIVE OF ORGANIZATION INTO
LINES/CLUSTERS.  PRIMARY NEGATIVES FOR SUSTAINED OR MORE WIDESPREAD
SEVERE WILL BE THE LIMITED LAPSE RATES AND RATHER WEAK LOW LEVEL
CONVERGENCE ACROSS THE REGION. HOWEVER...POTENTIAL FOR STORM-SCALE
ORGANIZATION AND AMOUNT INSTABILITY...ALONG WITH STEEPENING LOW
LEVEL LAPSE RATES...SHOULD SUPPORT DAMAGING WINDS THIS
AFTERNOON/EVENING.  IN ADDITION...PW/S AROUND 2 INCHES AND RICH LOW
LEVEL MOISTURE SOURCE WILL ENHANCE HEAVY RAINFALL POTENTIAL AS
THUNDERSTORMS INCREASE THROUGH THE AFTERNOON AND SPREAD EWD OFF THE
COAST BY THE EARLY TO MID EVENING /REFERENCE LATEST QPF GUIDANCE
FROM HPC/.

...NRN PLAINS INTO THE NRN MS RIVER VALLEY AND NRN GREAT LAKES...
MODELS STILL IN AGREEMENT IN INCREASING THUNDERSTORMS NEAR SURFACE
COLD FRONT NOW EXTENDING ACROSS NRN MN AS IT SAGS SSEWD INTO NRN WI
WRN U.P. OF MI THIS AFTERNOON. WARM SECTOR WILL REMAIN VERY MOIST
WITH 70+F SURFACE DEW POINTS ALREADY IN PLACE OVER NRN MI/NRN WI. 
MODIFIED 12Z SOUNDINGS AT MPX AND GRB AND RUC FORECAST SOUNDINGS 
ACCOUNTING FOR MID/UPPER 90F SURFACE TEMPERATURES AND DEW POINTS
AROUND 70F INDICATE MLCAPE WILL EXCEED 2500 J/KG OVER MUCH OF THIS
REGION WITH LITTLE OR NO MLCIN BY 21Z. IN ADDITION...THE 12Z
SOUNDING AT INL INDICATES 40 KT OF FLOW AROUND 3 KM WHICH IS
FORECAST TO OVERSPREAD THE NRN GREAT LAKES THROUGH THE DAY.  AS CAP
WEAKENS...SURFACE FRONT SHOULD SUPPORT INCREASED THUNDERSTORM
DEVELOPMENT FROM PORTIONS OF NRN/CENTRAL MN ACROSS NRN WI INTO THE
WRN U.P. OF MI.  DEEP LAYER SHEAR FROM 25-35 KT IS FORECAST TO BE
MARGINAL FOR SUPERCELLS...BUT MORE THAN ADEQUATE FOR LINES/CLUSTERS
GIVEN EXTREME INSTABILITY.  DAMAGING WINDS WILL LIKELY BE PRIMARY
SEVERE THREAT AS STORMS SHIFT SEWD THROUGH THE EVENING...THOUGH AN
ISOLATED TORNADO THREAT MAY ALSO ACCOMPANY ANY SUSTAINED SUPERCELL
STRUCTURE ESPECIALLY AS WLY LLJ INCREASES EARLY THIS EVENING.

SEVERE THREAT SHOULD THEN SHIFT NWWD INTO ND ALONG NOSE OF A SLY
LLJ...WHICH THE VEERS TO MORE SWLY LATER TONIGHT AHEAD OF SHORTWAVE
TROUGH NOW SKIRTING NWRN MT.  THIS SYSTEM WILL LIKELY RIDE EWD
ACROSS ND ATOP LARGER UPPER RIDGE AND TURN SEWD INTO NRN MN BY THE
END OF THE PERIOD.  ELEVATED STORMS WILL LIKELY DEVELOP AFTER DARK
INTO ND ALONG NOSE OF INCREASING LLJ ALONG AND NORTH OF SURFACE COLD
FRONT EXPECTED TO STALL E-W NEAR THE SD-ND BORDER.  VERY STEEP MID
LEVEL LAPSE RATES...FEED OF ABUNDANT LOW LEVEL MOISTURE AND STRONG
CLOUD-LAYER SHEAR SUGGEST ACTIVITY WILL BECOME INCREASINGLY
ORGANIZED/INTENSE AFTER 03Z AND BUILD UPSCALE AS AN MCS ACROSS ERN
ND INTO NWRN MN LATER TONIGHT. WARM MID LEVEL AIR MASS MAY ACT TO
HINDER HAIL GROWTH...THOUGH LARGE HAIL WILL LIKELY ACCOMPANY
STRONGER CORES GIVEN EFFECTIVE SHEAR AROUND 50 KT AND LIKELIHOOD OF
ELEVATED SUPERCELLS.  OVERALL SETUP WILL BECOME INCREASINGLY
FAVORABLE FOR SEVERE MCS DEVELOPMENT...POSSIBLY IN THE FORM OF A BOW
ECHO SYSTEM...ESPECIALLY IF STORMS CAN ROOT INTO SHALLOWER STABLE
LAYER NEAR THE SURFACE FRONT LATER TONIGHT WHICH WILL CONTINUE INTO
THE DAY 2 FORECAST PERIOD.

...AZ...
WELL DEFINED MID/UPPER LEVEL INVERTED TROUGH AND ASSOCIATED LOW
CENTER WILL CONTINUE A SLOW MOTION WSWWD INTO WRN AZ TODAY AND INTO
CENTRAL AZ LATER TONIGHT. AIR MASS REMAINS QUITE MOIST WITH LATEST
SURFACE ANALYSIS INDICATING MID 60S TO LOW 70 DEW POINTS IN PLACE
ACROSS S CENTRAL AND WRN AZ THIS MORNING. IN ADDITION...MID LEVEL
CLOUDS HAVE ALL BUT CLEARED MUCH OF CENTRAL AZ THIS MORNING WHICH
WILL ALLOW A MODERATE TO STRONGLY UNSTABLE AIR MASS TO DEVELOP AHEAD
OF THIS SYSTEM.  RUC FORECAST SOUNDINGS INDICATE MLCAPE WILL LIKELY
EXCEED 2500-3000 J/KG OVER LOWER ELEVATIONS GIVEN LOWER 70F SURFACE
DEW POINTS AND AFTERNOON HIGHS WELL INTO THE 90S.  AS LARGE SCALE
ASCENT INCREASES...STORMS WILL LIKELY BECOME WIDESPREAD OVER MUCH OF
AZ TODAY AND CONTINUE WELL INTO THE NIGHT.  APPEARS DAMAGING WINDS
AND VERY HEAVY RAINFALL...ALONG WITH SOME HAIL...WILL ACCOMPANY THIS
ACTIVITY.

..EVANS/GUYER.. 07/28/2006