DAY2SVR: Nws Storm Prediction Center Norman Ok

ACUS02 KWNS 090559
SWODY2
SPC AC 090557

DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT TUE APR 09 2013

VALID 101200Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MIDWEST TO THE WRN
GULF COAST...

...SYNOPSIS...
AN AMPLIFIED UPPER-LEVEL TROUGH WILL CONTINUE TO GRADUALLY PROGRESS
EWD FROM THE ROCKIES ACROSS THE GREAT PLAINS THROUGH EARLY THU. A
DOWNSTREAM MID-LEVEL RIDGE WILL BECOME CENTERED FROM THE SOUTHEAST
TO THE GREAT LAKES. AT THE SURFACE...A CYCLONE SHOULD SLOWLY MOVE
EWD FROM NRN MO ACROSS CNTRL IL. AN ATTENDANT SHARP COLD FRONT WILL
PUSH EWD AND REACH THE MID/LOWER MS VALLEY BY EARLY THU. A
QUASI-STATIONARY FRONT WILL BE DRAPED E OF THE MIDWEST CYCLONE TO
THE NRN APPALACHIANS.

...MIDWEST TO THE WRN GULF COAST...
A BROAD SWATH OF ORGANIZED SEVERE POTENTIAL IS EXPECTED DURING THE
PERIOD WITH SCATTERED DAMAGING WINDS...ISOLATED LARGE HAIL AND A FEW
TORNADOES APPEARING PROBABLE. OVERALL INTENSITY DOES NOT APPEAR TO
WARRANT A SIGNIFICANT SEVERE AREA WHICH MITIGATES A MODERATE RISK
ISSUANCE ATTM.

LOW-LEVEL MOISTURE WILL CONTINUE TO INCREASE FROM THE WRN/CNTRL GULF
COAST REGION WITH A PLUME OF 12-14 G/KG MEAN MIXING RATIOS SAMPLED
IN RAOBS MON EVENING. THIS SHOULD YIELD AN INCREASINGLY BROAD WARM
SECTOR WITH SURFACE DEW POINTS REACHING THE LOWER 60S ACROSS THE
MIDWEST TO THE UPPER 60S IN THE WRN GULF COAST STATES BY WED
AFTERNOON. PRESENCE OF A ROBUST EML PLUME THAT HAS BEEN
MAINTAINED/ADVECTED EWD OVER MUCH OF THE S-CNTRL/SERN CONUS IN
RECENT DAYS HAS FAVORABLY CONTRIBUTED TO STEEP MID-LEVEL LAPSE
RATES. AS SURFACE HEATING OCCURS...COMBINATION OF THE AFOREMENTIONED
FACTORS WILL LIKELY RESULT IN A BROAD MODERATELY UNSTABLE AIR MASS.

GUIDANCE CONTINUES TO DIFFER WITH THE EVOLUTION OF A SRN HIGH PLAINS
SHORTWAVE IMPULSE...WITH THE ECMWF CONSISTENTLY SLOWER AND ON A MORE
N/NELY TRACK TOWARDS THE MID-MO VALLEY THAN THE GFS.
THIS YIELDS A SLOWER EWD PROGRESSION OF THE SURFACE COLD FRONT AND
LOW/MID-LEVEL S/SWLYS NOT AS INTENSE OVER THE WARM
SECTOR. STILL...LOW/DEEP-LAYER SHEAR WILL BE FAVORABLE FOR ORGANIZED
CLUSTERS OF SUPERCELLS AND BOWING LINE SEGMENTS.

CONVECTION WILL BE ONGOING AT 12Z/WED FROM THE SRN PLAINS TO THE
LOWER MO VALLEY. CONVECTION-ALLOWING MODELS SUGGEST MUCH OF THIS
WILL BE BEHIND THE SHARP COLD FRONT...AS STRONG CAPPING MITIGATES
WARM SECTOR DEVELOPMENT. HOWEVER...WITH DIURNAL HEATING AND MODERATE
MID-LEVEL HEIGHT FALLS...CONVECTION WILL INCREASE ALONG BOTH FRONTAL
ZONES...LIKELY BECOMING WIDESPREAD BY WED EVENING. MIXED CONVECTIVE
MODE WOULD BE MOST LIKELY ACROSS PARTS OF THE MIDWEST WHERE A MIX OF
SEVERE HAZARDS IS ANTICIPATED. WITH SRN EXTENT...MORE MERIDIONAL
FLOW FIELDS NEARLY PARALLEL TO THE COLD FRONT WITH SOME ASPECT OF
VEER-BACK-VEER PROFILES SHOULD BE CONDUCIVE TO A PREDOMINANT LINEAR
MODE WITH DAMAGING WINDS AND A FEW TORNADOES AS THE PRIMARY HAZARDS.

..GRAMS.. 04/09/2013

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