National Weather Service Raw Text Product

166 
ACUS01 KWNS 091632
SWODY1
SPC AC 091630

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CDT THU APR 09 2015

VALID 091630Z - 101200Z

...THERE IS AN ENH RISK OF SVR TSTMS FROM THE ARKLATEX NORTHEAST
INTO THE SRN GRT LKS/LWR OH VLY...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ENHD AREA FROM
E TX INTO THE UPR OH VLY...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE ABOVE AREAS
FROM S CNTRL TX TO THE CNTRL APPALACHIANS...

...SUMMARY...
SEVERE THUNDERSTORMS ARE LIKELY TODAY INTO TONIGHT OVER A BROAD
SWATH FROM PARTS OF TEXAS NORTHEASTWARD THROUGH THE LOWER AND
MID-MISSISSIPPI VALLEYS INTO THE OHIO VALLEY AND SOUTHERN GREAT
LAKES. THESE WILL PRODUCE DAMAGING WIND...HAIL...AND A FEW
TORNADOES...ONE OR TWO OF WHICH COULD BE STRONG.

...SYNOPTIC SETUP...
PROGRESSIVE...MULTI-STREAM FLOW WILL PREVAIL OVER THE CNTRL AND ERN
U.S. THIS PERIOD...DOWNSTREAM FROM WRN STATES SPLIT. STRONG
SHORTWAVE TROUGH NOW EXITING THE CNTRL HIGH PLNS SHOULD ACCELERATE
ENE INTO ERN IA THIS EVE...BEFORE FURTHER ACCELERATING AND TURNING
NE TO NEAR SSM EARLY FRI AS NRN BRANCH IMPULSE AMPLIFIES SE INTO MN.
AT THE SAME TIME...WEAKER LEAD DISTURBANCE NOW CROSSING THE OZARKS
SHOULD MOVE NE INTO THE MID-OH VLY BY THIS EVE...AND INTO NY/PA
EARLY FRI...AS DEEP SWLY FLOW STRENGTHENS ACROSS THE E-CNTRL AND ERN
U.S.

AT THE SFC...NW MO LOW EXPECTED TO DEEPEN NEWD INTO SRN WI BY THIS
EVE...AND UNDERGO FURTHER DEEPENING AS IT REACHES THE SSM AREA EARLY
FRI. COLD FRONT TRAILING SSW FROM THE LOW SHOULD STRENGTHEN AND
ACCELERATE E ACROSS THE MID-MISSISSIPPI VALLEY AND OZARKS BY LATE
TODAY...AND INTO THE UPR OH...TN...AND LWR MS VLYS EARLY FRI...WHILE
MORE DIFFUSE WARM FRONT ADVANCES N INTO LWR MI.

IN SUMMARY...THE OVERALL SET-UP SUPPORTS A BROAD AREA WITH AN
APPRECIABLE RISK FOR SVR WEATHER LATER TODAY THROUGH EARLY FRI...BUT
WITH MITIGATING FACTORS THAT LIKELY WILL KEEP THE CORRIDORS OF
GREATEST RISK SOMEWHAT FRAGMENTED AND MULTI-MODAL.

...MID-MS VLY TO SRN GRT LKS THIS AFTN THROUGH EARLY TNGT...
SEVERAL FACTORS MAY COMBINE TO YIELD A MESOSCALE CORRIDOR OF
SOMEWHAT ENHANCED SVR THREAT...INCLUDING THE POTENTIAL FOR A COUPLE
STRONG TORNADOES...OVER THE ERN IA/NE MO/NRN IL/SRN WI AREA LATER
TODAY INTO EARLY TNGT. PERSISTENT HEIGHT FALLS ACROSS
REGION...LARGELY DUE TO AMPLIFICATION OF UPSTREAM...LARGER-SCALE
TROUGH...WILL OFFSET SINKING/DESCENT OCCURRING IN WAKE OF LEAD UPR
IMPULSE AND EMBEDDED MCV NOW CROSSING THE OZARKS. AT THE SAME
TIME...SATELLITE SUGGESTS LIKELIHOOD FOR AT LEAST MODEST SFC HEATING
AHEAD OF COLD FRONT AND DEEPENING SFC LOW APPROACHING FROM NW MO.

WITH 700 MB SWLY WINDS INCREASING TO AOA 60 KTS ATOP 40+ KT SSW FLOW
AT 850 MB...HODOGRAPHS WILL BE FAVORABLE FOR SUSTAINED SUPERCELLS
WITH LARGE HAIL. THE DIRECTIONAL COMPONENT TO LOW-LVL SHEAR LIKELY
WILL NOT BE GREAT. BUT COMBINATION OF STRENGTHENING FLOW AND
EXPECTED BACKING OF NEAR-SFC WINDS/ENHANCED SRH IMMEDIATELY AHEAD OF
SFC LOW SUGGEST THAT A CORRIDOR OF HEIGHTENED TORNADO POTENTIAL
COULD EVOLVE LATER THIS AFTN...BEFORE THE STORMS MERGE INTO BROKEN
LINES/SMALL CLUSTERS EARLY TNGT. ALTHOUGH CLOUDS AND SHOWERS MAY
DELAY NWD ADVANCE OF WARM FRONT ACROSS IL/IND...STRENGTHENING SFC
PRESSURE FALLS/TRACK OF SFC LOW FURTHER INDICATE THAT THE SVR THREAT
COULD EXTEND NWD INTO SRN WI AND SW LWR MI...WITH DMGG WINDS
BECOMING THE DOMINANT THREAT OVER TIME.

...LWR OH VLY SW INTO E TX/LWR MS VLY LATE TODAY THROUGH EARLY
FRI...

SFC HEATING AND UPLIFT ALONG COLD FRONT AND PRE-FRONTAL CONFLUENCE
AXES EXPECTED TO INITIATE TSTMS LATER TODAY THROUGH TNGT AS EML CAP
IS BROKEN. ALTHOUGH WIND FIELDS WILL BE WEAKER RELATIVE TO POINTS
N...AMPLE /40+ KT/ WSWLY DEEP SHEAR WILL EXIST FOR SUSTAINED
STORMS/SUPERCELLS...ESPECIALLY OVER THE LWR OH AND TN VLYS. GIVEN
FAIRLY RICH MOISTURE AVAILABILITY /PW AOA 1.50 INCHES/...IN THEIR
EARLY STAGES THESE STORMS COULD YIELD LARGE HAIL AND A FEW
TORNADOES. WITH TIME...DEGREE OF LOW-LVL FORCING SHOULD RESULT INTO
AMALGAMATION OF CONVECTION INTO AN EXTENSIVE...BROKEN SQLN. EMBEDDED
LEWPS AND BOWING STRUCTURES LIKELY WILL BE ACCOMPANIED BY A SLOWLY
DIMINISHING RISK FOR DMGG WIND INTO EARLY FRI.

...UPR OH LY/CNTRL APPALACHIANS THIS AFTN/EVE...
A CONDITIONAL RISK WILL EXIST FOR LOOSELY-ORGANIZED CLUSTERS OF
MAINLY MULTICELL STORMS WITH HAIL AND LOCALLY DMGG WIND THIS AFTN
OVER PARTS OF OH...KY AND WRN SLOPES OF THE CNTRL
APPALACHIANS...WHERE SFC HEATING WILL FURTHER DESTABILIZE REGION OF
MODEST LOW-LVL MOISTURE AND MID-LVL INSTABILITY. SOME OF THIS
ACTIVITY COULD ARISE FROM EXISTING AREAS OF ELEVATED CONVECTION NOW
OVER PARTS OF THE REGION...WITH OTHER STORMS INITIATED BY
DIFFERENTIAL HEATING ALONG RESIDUAL SFC BOUNDARIES. MOST OF THE
STORMS SHOULD WEAKEN WITH NIGHTFALL...ALTHOUGH PARTS OF THE OH VLY
COULD EXPERIENCE A SECOND ROUND OF STORMS LATE TNGT AS MID MS VLY
COLD FRONT APPROACHES REGION.

..CORFIDI/GRAMS/MOSIER.. 04/09/2015