[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 110610
SWODY2
SPC AC 110609

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0109 AM CDT TUE JUL 11 2006

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CENTRAL APPALACHIANS
INTO SWRN NEW ENGLAND...

...SYNOPSIS...
BROAD POSITIVELY TILTED MID LEVEL TROUGH IS EXPECTED TO MOVE EWD
FROM THE GREAT LAKES/MID MS VALLEY ACROSS THE OH VALLEY AND TOWARD
NEW ENGLAND.  MEANWHILE...PRIMARY BELT OF WESTERLIES IS EXPECTED TO
EXTEND FROM THE PACIFIC NW INTO SRN AND ERN CANADA.  MODELS REMAIN
DIFFERENT WITH THE TIMING OF A SHORT WAVE TROUGH EXPECTED TO
TRANSLATE ENEWD ACROSS THE NRN HIGH PLAINS TO SOUTH CENTRAL CANADA
DURING DAY 2 FORECAST PERIOD.

NAM/NAMKF INDICATED A MID LEVEL SHORT WAVE TROUGH AND ATTENDANT
SURFACE LOW APPROACHING THE E/SE COAST OF FL WEDNESDAY AFTERNOON...
WITH THIS SYSTEM THEN TURNING NWD ALONG THE N FL COAST WEDNESDAY
NIGHT. IF THIS SYSTEM DOES DEVELOP AS FORECAST BY THE NAM/NAMKF...
AND MOVES CLOSER TO THE COAST THAN CURRENTLY FORECAST ENHANCING LOW
LEVEL DIRECTIONAL SHEAR...THEN SEVERE PROBABILITIES MAY BE REQUIRED
IN LATER OUTLOOKS.

...SRN NEW ENGLAND TO CENTRAL APPALACHIANS AND OH VALLEY...
IN THE LOW LEVELS...A SURFACE LOW ASSOCIATED WITH THE BROAD MID
LEVEL TROUGH IS EXPECTED TO BE LOCATED OVER THE SRN GREAT LAKES
REGION AT 12Z WEDNESDAY.  THIS LOW IS FORECAST TO TRACK EWD REACHING
SRN NEW ENGLAND BY 12Z THURSDAY...WHILE THE TRAILING SURFACE
BOUNDARY SPREADS EWD ACROSS NY/PA AND SWD INTO THE OH VALLEY.

THUNDERSTORMS ARE EXPECTED TO BE ONGOING ALONG/AHEAD OF THE SURFACE
TROUGH AT 12Z WEDNESDAY FROM THE LOWER GREAT LAKES REGION SWWD
THROUGH THE OH VALLEY IN ASSOCIATION WITH WAA ALONG A 40-50 KT SWLY
LLJ AXIS.  AIR MASS DOWNSTREAM OF THIS INITIAL ACTIVITY IS EXPECTED
TO DESTABILIZE GIVEN RICH MOISTURE /SURFACE DEWPOINTS IN THE UPPER
60S TO AROUND 70/ ADVECTION AND SURFACE HEATING ESPECIALLY ACROSS
THE SRN HALF OF THE SLIGHT RISK AREA.  WEAK MID LEVEL LAPSE RATES
SHOULD LIMIT THE DEVELOPMENT OF STRONGER INSTABILITY WITH MLCAPE
RANGING FROM 500-1000 J/KG.  DESPITE POTENTIAL FOR MARGINAL
INSTABILITY...STRONG /40-50 KT/ WSWLY LOW-MID LEVEL WINDS SHOULD
COMPENSATE FOR THIS LIMITING FACTOR...AND SUPPORT A THREAT FOR
DAMAGING WINDS AS ONGOING STORMS AND/OR NEW LINE SEGMENTS DEVELOP
EWD ACROSS THE SLIGHT RISK AREA.  STRONG DEEP LAYER SHEAR ALSO
SUGGESTS SUPERCELLS WILL BE POSSIBLE WITH STRONG LOW LEVEL SHEAR
VALUES SUPPORTING A TORNADO THREAT...ESPECIALLY ACROSS NRN MD/ERN PA
TO SERN NY WHERE INSTABILITY SHOULD BE MAXIMIZED AND MLCAPE
POTENTIALLY REACH 1500 J/KG.

FARTHER SOUTHWEST THROUGH THE OH VALLEY...THE AIR MASS SHOULD BECOME
MODERATELY UNSTABLE SOUTH OF INITIAL CONVECTIVE ACTIVITY SUPPORTING
NEW THUNDERSTORMS THROUGH DAY 2.  WEAKER DEEP LAYER SHEAR WITH SWWD
EXTENT IS EXPECTED TO LIMIT THE SEVERE WEATHER THREAT ACROSS THE OH
VALLEY.

...PLAINS STATES...
SLY LOW LEVEL FLOW ACROSS THE PLAINS STATES IS EXPECTED TO ADVECT
MOISTURE NWD...WHILE STRONG SURFACE HEATING AND DEEP BOUNDARY LAYER
MIXING WITHIN THIS AIR MASS SHOULD RESULT IN LARGE SURFACE
TEMPERATURE/DEWPOINT SPREADS BY PEAK HEATING WEDNESDAY AFTERNOON.
STEEP LAPSE RATES WILL SUPPORT MODERATE INSTABILITY /MLCAPE
1500-2500 J/KG/ DEVELOPING FROM OK AND TX PANHANDLE NWD TO THE
DAKOTAS.  IN ADDITION TO MODEL DIFFERENCES WITH THE TIMING OF THE
MID LEVEL IMPULSE TO AFFECT THE NRN PLAINS...THERE IS LARGE MODEL
SPREAD IN THE SPEED OF WLY MID LEVEL FLOW EXPECTED ACROSS THE
CENTRAL/SRN PLAINS.  DESPITE THESE DIFFERENCES...THIS OUTLOOK WILL
INDICATE LOW SEVERE PROBABILITIES...GIVEN THAT EVEN WEAK DEEP LAYER
SHEAR /20-25 KT/ WITHIN A MODERATELY UNSTABLE ENVIRONMENT WILL
SUPPORT A FEW SEVERE STORMS.  ACTIVITY SHOULD BE FOCUSED ALONG THE
LEE TROUGH WHICH WILL MOVE EWD INTO THE NRN PLAINS BY LATER IN THE
FORECAST PERIOD.  A FEW SEVERE STORMS WILL ALSO BE POSSIBLE ALONG A
TRAILING COLD FRONT INTO SRN MT WHERE DEEP LAYER SHEAR WILL BE
SUFFICIENT FOR ORGANIZED STORMS...BUT INSTABILITY MAY BE WEAKER.

..PETERS.. 07/11/2006