DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 162003
SWODY1
SPC AC 162000

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT TUE JUL 16 2013

VALID 162000Z - 171200Z

...NO SVR TSTM AREAS FORECAST...

...DISCUSSION...

CURRENT FORECAST APPEARS ON TRACK WITH ONLY MINOR CHANGES MADE FOR
THE 20Z UPDATE. STORMS ARE DEVELOPING IN POST FRONTAL ZONE OVER NRN
ND WHERE VERTICAL SHEAR IS STRONG...BUT INSTABILITY IS SOMEWHAT
LIMITED. FARTHER EAST...ADDITIONAL STORMS MAY DEVELOP ALONG SURFACE
FRONT WHERE A LINE OF SHALLOW CUMULUS IS INDICATED IN VISIBLE
IMAGERY OVER NWRN MN. HOWEVER...VERTICAL SHEAR IN THAT REGION ALONG
AND SOUTH OF THE FRONT IS WEAKER...AND MID-LEVEL LAPSE RATES ARE
MODEST. STORMS MAY STILL BECOME CAPABLE OF PRODUCING ISOLATED STRONG
WIND GUSTS AND HAIL FROM CNTRL-NERN ND INTO NRN MN THIS
EVENING...BUT OVERALL THREAT DOES NOT APPEAR TO WARRANT MORE THAN 5%
SEVERE PROBABILITIES.

..DIAL.. 07/16/2013

.PREV DISCUSSION... /ISSUED 1130 AM CDT TUE JUL 16 2013/

...SYNOPSIS...
OH VLY RIDGE WILL BUILD W INTO ERN PORTIONS OF THE PLAINS THIS
PERIOD AS NM-TX UPR LOW CONTINUES SLOWLY WSWWD. BELT OF WLYS ON THE
NRN SIDE OF THE RIDGE WILL RETREAT A BIT FARTHER N INTO CANADA AS
UPR IMPULSE RESPONSIBLE FOR YESTERDAYS SVR STORMS IN MT-ND CONTINUES
NE TO HUDSON BAY. IN THE WEST...LOW NOW OFF THE CA CST SHOULD MOVE N
AS A SHORTWAVE TROUGH ACROSS NRN CA/WRN ORE...ENHANCING SLY MID/UPR
LVL FLOW OVER THE INTERIOR NORTHWEST.

EXCEPT ALONG THE CANADIAN BORDER AND IN THE PACIFIC NORTHWEST...DEEP
SHEAR WILL REMAIN WEAK OVER THE CONUS. LOW TO MID-LVL LAPSE RATES
ALSO WILL REMAIN WEAK EXCEPT OVER PARTS OF THE WEST. AS A
RESULT...THE RISK FOR ORGANIZED/SUSTAINED SVR STORMS APPEARS
MINIMAL. BUT POCKETS OF STRONG TO OCCASIONALLY SVR TSTMS MAY DEVELOP
WITH SFC HEATING LATER TODAY...MAINLY ALONG THE PERIPHERY OF THE OH
VLY RIDGE...AND ON ERN FRINGE OF UPR IMPULSE IN THE WEST.

...VA/NC/SC THIS AFTN/EVE...
LATEST SFC ANALYSIS SHOWS A DIFFUSE WSW-ENE TROUGH/WIND SHIFT ACROSS
S CNTRL/SE VA THAT SHOULD DRIFT SLOWLY SWD TODAY BENEATH MODEST /20
KT/ NELY FLOW ALOFT. SATELLITE AND SFC DATA ALSO SHOW A WEAK NW/SE
BOUNDARY/BACK-DOOR FRONT MOVING SW ACROSS THE LWR CHESAPEAKE BAY
REGION. THE INTERSECTION OF THESE FEATURES...GIVEN STRONG SFC
HEATING...WEAK CIN...AND FAIRLY MOIST ENVIRONMENT /PW AOA 1.75
INCHES/... MAY PROVIDE SUFFICIENT LOW-LVL UPLIFT TO SUPPORT STORM
DEVELOPMENT OVER SE VA BY EARLY AFTN. DEVELOPMENT ALSO MAY BE
FOSTERED BY WEAK UPR IMPULSE APPARENT IN WV IMAGERY DRIFTING SW FROM
THE WRN ATLANTIC.

WITH MLCAPE LIKELY INCREASING TO AROUND 2500 J PER KG...SETUP COULD
YIELD SCTD STORMS CAPABLE OF MARGINALLY SVR HAIL/LOCALLY DMGG WIND.
IF AN APPRECIABLE NUMBER OF STORMS DO FORM...NOT OUT OF THE QUESTION
GIVEN THE ENVIRONMENT DESCRIBED...THE ACTIVITY COULD MERGE INTO
SMALL CLUSTERS AS OUTFLOWS CONGEAL. ALTHOUGH WIDESPREAD SVR WINDS
ARE NOT EXPECTED...SUCH UPSCALE DEVELOPMENT MAY YIELD A FEW SWATHS
OF LOCALLY DMGG GUSTS THROUGH EARLY EVE.

...NRN PLNS TO UPR MS VLY/UPR GRT LKS TODAY/TNGT...
WSW-ENE COLD FRONT ASSOCIATED WITH SHORTWAVE TROUGH APPROACHING
HUDSON BAY WILL SETTLE SLOWLY S ACROSS ND AND NRN MN TODAY AS UPR
SYSTEM CONTINUES NEWD AWAY FROM REGION. CONVERGENCE ALONG THE
FEATURE SHOULD WEAKEN THROUGH THE DAY AS LOW-LVL JET STREAM LIFTS
NEWD INTO CANADA AND SFC WINDS AHEAD OF THE BOUNDARY VEER IN THE
U.S. THE FRONT WILL...NEVERTHELESS...SERVE A FOCUS FOR WEAK UPLIFT.
COUPLED WITH STRONG SFC HEATING...WEAK CIN...AND AMPLE MOISTURE /PW
AROUND 1.50 INCHES/...EXPECT WDLY SCTD STORMS TO FORM ALONG/AHEAD OF
IT FROM NE ND INTO NRN MN/UPR MI THIS AFTN.

CURRENT UPR AIR DATA AND FCST SOUNDINGS SHOW LARGELY UNIDIRECTIONAL
WSWLY WIND PROFILES WITH AMPLE DEEP SHEAR FOR SUSTAINED
STORMS/SUPERCELLS...ESPECIALLY GIVEN LIKELY PRESENCE OF 2500 J/KG
MLCAPE. DIMINISHING LARGE SCALE FORCING FOR ASCENT AND MODEST
LOW-LVL CONVERGENCE SHOULD LIMIT OVERALL SVR THREAT...ALTHOUGH ISOLD
SVR HAIL AND LOCALLY DMGG WIND GUSTS MAY OCCUR.

ADDITIONAL STORMS MAY FORM OVER THE SAME REGION TNGT THROUGH EARLY
WED IN RESPONSE TO MODEST NOCTURNAL INCREASE IN WAA/MOISTURE
TRANSPORT AS THE FRONT STALLS W-E ALONG THE ND-SD BORDER INTO CNTRL
MN. WHILE ISOLD INSTANCES OF SVR HAIL MAY OCCUR...WIDESPREAD SVR
ACTIVITY IS NOT EXPECTED.

...INTERIOR PACIFIC NW THIS AFTN THROUGH TNGT...
SEVERAL EPISODES OF HIGH-BASED TSTMS APPEAR LIKELY OVER INTERIOR
ORE/WA AND WRN ID THIS PERIOD AS PW INCREASES TO AROUND .75 INCH IN
CORRIDOR OF STRENGTHENING MID/UPR-LVL SLY FLOW/ASCENT ON ERN FRINGE
OF EJECTING SHORTWAVE TROUGH. STRONG SFC HEATING BENEATH THIS
ACTIVITY WILL YIELD AN INVERTED-V THERMODYNAMIC ENVIRONMENT
CONDUCIVE TO STRONG CONVECTIVELY-ENHANCED SFC GUSTS GIVEN EXPECTED
40 KT...UNIDIRECTIONAL CLOUD-LAYER FLOW. SETUP MAY YIELD A FEW
CLUSTERS/BANDS OF STORMS CAPABLE OF ISOLD TO WDLY SCTD DMGG GUSTS
THROUGH EARLY TNGT.

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