DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 062001
SWODY1
SPC AC 061959

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT THU SEP 06 2012

VALID 062000Z - 071200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE CENTRAL AND
SOUTHERN PLAINS INTO IA AND WEST CENTRAL IL...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE OZARKS INTO
SRN IL AND PART OF FAR WRN KY...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE LOWER GREAT
LAKES TO NORTHERN NEW ENGLAND...

...PARTS OF NRN PA THROUGH NY/VT...
THE SLIGHT RISK HAS BEEN EXPANDED TO INCLUDE A FEW ADDITIONAL
COUNTIES INTO NERN PA TO EAST CENTRAL NY AS THE AIR MASS HAS BECOME
MODERATELY UNSTABLE INCLUDING THESE AREAS. ALTHOUGH THE AIR MASS IS
ALSO MODERATELY UNSTABLE FARTHER SWD ACROSS THE REST OF
PA...STRONGER EFFECTIVE BULK SHEAR RESIDES IN THE LOWER GREAT LAKES
TO WRN NEW ENGLAND SUPPORTING STORM ORGANIZATION/SVR THREAT IN THE
SLIGHT RISK AREA.

...SRN/SERN MO...FAR NRN AR...AND SRN IL/FAR WRN KY...
GIVEN THE ORGANIZED N-S ORIENTED FORWARD PROPAGATING LINE SEGMENT
LOCATED IN CENTRAL TO SOUTH CENTRAL MO AND THE EWD EXTENT OF A
MODERATELY UNSTABLE AIR MASS INTO SRN IL/WRN KY...THE SLIGHT RISK
AND SEVERE PROBABILITIES FOR HAIL AND WIND HAVE BEEN EXPANDED TOWARD
THE N AND E.

...ELSEWHERE...
NO CHANGES WERE NEEDED WITH THE SLIGHT RISK IN THE PLAINS TO IA/WEST
CENTRAL IL AND THE LOW SEVERE WIND PROBABILITY.

..PETERS.. 09/06/2012

.PREV DISCUSSION... /ISSUED 1129 AM CDT THU SEP 06 2012/

...SYNOPSIS...
SEASONABLY FAST...LOW AMPLITUDE CYCLONIC FLOW WILL PREVAIL ACROSS
THE NRN THIRD OF THE NATION THIS PERIOD...S OF ELONGATED UPR LOW IN
NRN ONT AND N OF PERSISTENT SW/S CNTRL U.S. RIDGE. THIS PATTERN WILL
BEGIN TO AMPLIFY EARLY FRI AS STRONG SHORTWAVE IMPULSE NOW IN WRN MT
SHEARS ESE INTO THE NRN PLNS...AND PARTIALLY PHASES WITH A
DISTURBANCE DROPPING SWD ALONG THE W SIDE OF THE ONT LOW. IN THE
MEAN TIME...A SERIES OF WEAKER DISTURBANCES WILL CONTINUE TO TRACK
EWD WITHIN BELT OF ENHANCED FLOW IMMEDIATELY N OF THE UPR
RIDGE...AND A WEAK IMPULSE WILL GLANCE THE LWR GRT LKS. FARTHER
S...LONG-LIVED UPR VORT WILL PERSIST OFF THE E FL CST...WHILE
NEIGHBORING VORT MAX SAGS SLOWLY S ACROSS N CNTRL GULF OF MEXICO.

AT LWR LVLS...COLD FRONT ASSOCIATED WITH THE MT TROUGH SHOULD MOVE
STEADILY E/SE THROUGH THE PERIOD. THE FRONT WILL OVERTAKE LEE LOW
AND TROUGH...NOW IN SD...AS THOSE FEATURES TRACK E/SE TO NEAR SIOUX
FALLS BY THIS EVE. THE FRONT/LOW SHOULD CONTINUE E/SE
OVERNIGHT...AND EXTEND FROM NRN MI THROUGH SE IA TO SW KS BY 12Z
FRI. STRENGTHENING SLY GRADIENT FLOW WILL ALLOW RICH LOW-LVL
MOISTURE TO SPREAD NNE TOWARD COLD FRONT AND LEE TROUGH. COUPLED
WITH SFC HEATING AND INCREASING LARGE SCALE ASCENT WITH AMPLIFYING
UPR TROUGH...EXPECT THAT SEVERAL AREAS OF STRONG TO POSSIBLY SVR
TSTMS WILL FORM ALONG THE LEE TROUGH LATER TODAY...AND ALONG THE
FRONT TNGT AND EARLY FRI. SOME OF THE STORMS COULD PERSIST THROUGH
12Z FRI OVER THE MID MS VLY.

...TX/OK PNHDLS TO CNTRL PLNS THIS AFTN/EVE...
FORCING FOR ASCENT WILL REMAIN WEAK OVER WRN PARTS OF THE SRN/CNTRL
PLNS TODAY...BENEATH A DEEP EML. THESE FACTORS SHOULD DELAY DIURNAL
TSTM DEVELOPMENT ALONG/AHEAD OF LEE TROUGH/DRYLINE TIL LATE IN THE
DAY. ONCE STORMS DO FORM...MOST LIKELY INITIALLY OVER WRN AND NRN
KS...PRESENCE OF MODERATE TO STRONG INSTABILITY /SBCAPE TO 2000 J
PER KG/ AND 35+ KT WNWLY DEEP SHEAR SUGGEST LIKELIHOOD FOR A FEW
SUSTAINED STORMS/SUPERCELLS WITH LARGE HAIL/DMGG WIND. THE GREATEST
THREAT SHOULD EVOLVE FROM CNTRL/NRN KS INTO SRN NEB DURING THE
EVE...WITH MORE ISOLD ACTIVITY MAINLY POSING A WIND THREAT SWD INTO
OK/TX. ONE OR TWO MCSS MAY FORM BY LATE EVE. THESE COULD POSE A
DIMINISHING RISK FOR SVR HAIL/WIND INTO THE NIGHT OVER KS AND
PERHAPS WRN OK AND/OR THE ERN TX PNHDL.

...MID MO/MID MS VLYS TNGT/EARLY FRI...
TSTMS SHOULD INCREASE IN COVERAGE AND STRENGTH OVER PARTS OF ERN
NE...SE SD...IA AND MN AFTER 00Z FRI AS SWLY LLJ/MOISTURE INFLOW
INCREASE WITH THE CONTINUED APPROACH OF AMPLIFYING UPR TROUGH.
STORMS SHOULD FOCUS NEAR/E OF SFC LOW MOVING ESE FROM NEB/SD... AND
MAY BE SLIGHTLY ELEVATED. NEVERTHELESS...WITH MUCAPE AROUND 1000
J/KG AND STRONG CLOUD-LAYER SHEAR /500 MB WNW FLOW AOA 50
KTS/...POTENTIAL WILL EXIST FOR SVR HAIL AND POSSIBLY LOCALLY DMGG
WIND. THIS ACTIVITY COULD REACH NW IL BY THE END OF THE PERIOD.

...OZARKS THIS AFTN...
SATELLITE SHOWS A SRN STREAM IMPULSE NOW IN SE KS THAT SHOULD
CONTINUE E ACROSS THE OZARKS LATER TODAY. ASSUMING THAT THE 12Z SGF
RAOB IS AND WILL REMAIN REPRESENTATIVE OF THE DOWNSTREAM ENVIRONMENT
THROUGH LATER TODAY...AMPLE INSTABILITY SHOULD DEVELOP TO SUPPORT A
CONDITIONAL RISK FOR SVR STORMS GIVEN DEEP EML AND RICH LOW-LVL
MOISTURE. EXPECT THAT SFC HEATING WILL FOSTER ADDITIONAL STORM
DEVELOPMENT ON DOWNWIND SIDE OF EXISTING SLIGHTLY ELEVATED STORM
CLUSTER NOW IN SE KS. THIS ACTIVITY SHOULD FOCUS ALONG AND N OF WEAK
W-E FRONT STALLED OVER THE REGION. THE STORMS MAY GROW INTO A SMALL
MCS CAPABLE OF SVR HAIL AND WIND THAT MOVES ESE TOWARD THE MS RVR.

...LWR OH VLY TO LWR GRT LKS THIS AFTN...
WDLY SCTD TO SCTD TSTMS SHOULD FORM OVER PARTS OF OH...NRN PA...AND
UPSTATE NY...WHERE MODERATE DEEP WLY FLOW WILL PREVAIL ON SRN FRINGE
OF ELONGATED UPR LOW OVER ONT. LARGE SCALE FORCING FOR ASCENT
APPEARS NEUTRAL AT BEST...PER SATELLITE AND MODEL DATA.
NEVERTHELESS...AREA SOUNDING SHOW AMPLE MOISTURE PRESENT FOR STORMS
AND MINIMAL CIN. WITH DEEP FLOW LARGELY PARALLEL TO THE LONG AXES OF
THE LAKES...EXPECT THAT LAKE BOUNDARIES MAY SERVE AS THE MAIN FOCI
FOR LOW-LVL UPLIFT/STORM DEVELOPMENT. THIS ACTIVITY MAY ORGANIZE
SEVERAL SHORT BANDS. WITH AFTN SBCAPE AVERAGING AROUND 1500 J/KG AND
30 KT WLY DEEP SHEAR...SETUP COULD YIELD A FEW SMALL BOWS WITH
LOCALLY DMGG WIND.

DEEP SHEAR SHOULD DIMINISH WITH SW EXTENT THROUGH THE OH VLY...
BUT BOTH INSTABILITY AND SHEAR MAY PROVE SUFFICIENT FOR
ISOLD/BRIEFLY SVR STORMS.

...VA TIDEWATER/ERN NC THIS AFTN...
A FEW STRONG TO ISOLD SVR STORMS MAY OCCUR OVER THE LWR CHESAPEAKE
BAY AND ERN NC TODAY...WHERE A BELT OF 20-25 KT 700-500 MB WSW FLOW
WILL LINGER PARALLEL TO AN AXIS OF VERY MOIST /PW AOA 2 INCHES/ AIR.
STORMS SHOULD FOCUS ALONG WEAK W-E FRONT NOW EXTENDING ENE FROM S
CNTRL VA...AND POSSIBLE ALONG SW-NE LEE TROUGH IN NC. UPLIFT ALSO
MAY BE AIDED BY WEAK MID LVL SHEAR LOBE THAT APPEARS TO BE EDGING E
TOWARD REGION IN WV IMAGERY. STORMS LIKELY WILL MERGE INTO SMALL
CLUSTERS/SHORT LINES...AND MAY POSE A RISK FOR LOCALLY DMGG WIND.

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