Day 1 Severe Thunderstorm Outook
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Categorical Day1 1200Z Outlook
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Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
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Probability of one inch diameter hail or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of two inch diameter hail or larger within 25 miles of a point.
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Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% or greater probability of wind gusts 65 knots or greater within 25 miles of a point.
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Images courtesy of the NWS Storm Prediction Center
000
ACUS01 KWNS 200550
SWODY1
SPC AC 200548
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT THU JUN 20 2013
VALID 201200Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS FOR THE NRN/CNTRL PLAINS AND
UPPER MS VALLEY...
...SYNOPSIS...
A LARGE UPPER TROUGH WILL RESIDE ACROSS THE WRN CONUS DURING THE D1
FORECAST PERIOD...WHILE DOWNSTREAM...AN UPPER RIDGE WILL BE PRESENT
FROM THE MO VALLEY INTO THE UPPER MS VALLEY. A SHORTWAVE TROUGH
LOCATED OVER THE NRN ROCKIES EARLY THIS MORNING WILL LIFT NWD AROUND
THE ERN EDGE OF THE LARGER-SCALE WAVE INTO CANADA BY LATE MORNING.
AS THIS OCCURS...A SURFACE LOW PRESSURE SYSTEM WILL OCCLUDE...WITH A
COLD FRONT/OCCLUDED FRONT ARCING NWWD FROM THE DAKOTAS INTO SRN
ALBERTA...AND A WARM FRONT EXTENDING SEWD FROM CNTRL ND INTO E-CNTRL
MN. THE SRN PORTION OF THE COLD FRONT WILL THEN TRAIL SWWD INTO THE
CNTRL HIGH PLAINS...WHERE A SECOND AREA OF LOW PRESSURE IS FORECAST
TO RESIDE LATER IN THE AFTERNOON.
...NRN/CNTRL PLAINS AND UPPER MS VALLEY...
A BROAD AREA OF SLY LOW-LEVEL FLOW WILL AID IN TRANSPORTING MID 60S
DEWPOINTS INTO THE NRN PLAINS AND UPPER MS VALLEY AHEAD OF THE
SURFACE OCCLUDED/COLD FRONT...WITH UPPER 60S DEWPOINTS POSSIBLE OVER
ERN NEB AND WRN IA. BY MIDDAY...AN EML IS FORECAST TO SPREAD ACROSS
THE AREA...WITH STEEP MIDLEVEL LAPSE RATES COMBINED WITH SURFACE
TEMPERATURES IN THE 80S AND A MOIST BOUNDARY LAYER AIDING IN MLCAPE
VALUES AOA 2000 J/KG.
LATEST MODEL GUIDANCE INDICATES UPPER FORCING FOR ASCENT WILL BE
NEBULOUS THROUGH LATE AFTERNOON...WITH WEAK/SUBTLE MIDLEVEL
VORTICITY MAXIMA EJECTING NEWD FROM THE WRN TROUGH.
HOWEVER...CURRENT THINKING IS AN MCV EMANATING FROM AN MCS OVER ERN
MT EARLY THIS MORNING WILL ROUND THE UPPER RIDGE AND AID IN RENEWED
THUNDERSTORM DEVELOPMENT BY AFTERNOON ALONG AND N OF THE WARM FRONT
OVER ERN ND AND NRN/CNTRL MN. THIS ACTIVITY MAY QUICKLY GROW UPSCALE
INTO ANOTHER MCS AND MOVE SEWD ALONG THE WARM FRONT. DAMAGING WINDS
AND LARGE HAIL WILL BE THE PRIMARY THREATS...BUT A COUPLE OF
TORNADOES WILL ALSO BE POSSIBLE. MCS MAINTENANCE WILL CONTINUE TO BE
SUPPORTED INTO THE NIGHT AS A SWLY LOW-LEVEL JET STRENGTHENS AND
EXPANDS NWD INTO THE UPPER MS VALLEY.
ELSEWHERE OVER SD INTO NEB/IA...AFTERNOON DESTABILIZATION WILL
SUPPORT A CHANCE FOR ISOLATED THUNDERSTORM DEVELOPMENT EVOLVING OFF
THE COLD/OCCLUDED FRONT EWD ACROSS THE WARM SECTOR. MID AND
UPPER-LEVEL SWLY FLOW NEAR 30 KT WILL RESIDE ABOVE LOW-LEVEL
SSELYS...WHICH WILL YIELD VERTICAL SHEAR PROFILES FAVORABLE FOR
ORGANIZED MULTICELL CLUSTERS AND A FEW SUPERCELLS. GIVEN MODERATE TO
STRONG CAPE AND STEEP MIDLEVEL LAPSE RATES...DAMAGING WINDS AND
LARGE HAIL WILL BE POSSIBLE.
...WRN NEB/NEB PANHANDLE...FAR SERN WY...
LOW-LEVEL WINDS ARE FORECAST TO BE OUT OF THE E OVER WRN NEB AS A
COLD FRONT STALLS OVER THE CNTRL HIGH PLAINS. THIS WILL AID IN
MAINTAINING A MOIST LOW-LEVEL AIRMASS OVER THE NEB PANHANDLE/FAR
SERN WY...WITH SURFACE DEWPOINTS IN THE 50S...AND WILL SUPPORT WEAK
TO MODERATE INSTABILITY WITH THE OCCURRENCE OF DAYTIME HEATING AND
THE PRESENCE OF STEEP MIDLEVEL LAPSE RATES. THUS...A FEW ISOLATED
THUNDERSTORMS CANNOT BE RULED OUT WITHIN THE UPSLOPE FLOW REGIME. IF
THIS OCCURS...SHEAR PROFILES WILL BE FAVORABLE FOR SUPERCELLS POSING
A THREAT FOR LARGE HAIL AND A TORNADO. HOWEVER...THIS SCENARIO IS
UNCERTAIN ATTM...WHICH PRECLUDES A CATEGORICAL UPGRADE. THE MORE
LIKELY SCENARIO IS FOR STORMS TO DEVELOP OVERNIGHT AS AN UPPER
IMPULSE EJECTS EWD INTO THE HIGH PLAINS. THESE STORMS WOULD LIKELY
BE ELEVATED AND POSE AN ISOLATED THREAT FOR LARGE HAIL.
...ERN NM...W TX/TX PANHANDLE...
DEWPOINTS IN THE 50S TO NEAR 60F ARE FORECAST TO RESIDE OVER THE SRN
HIGH PLAINS THIS AFTERNOON IN THE PRESENCE OF STRONG SURFACE HEATING
AND STEEP LAPSE RATES. THIS WILL YIELD MODERATE INSTABILITY
SUPPORTIVE OF THUNDERSTORM CLUSTERS...WITH STORM INITIATION POSSIBLY
AIDED BY A WEAK UPPER IMPULSE ENTERING THE REGION BY EVENING.
ISOLATED DAMAGING WINDS AND LARGE HAIL WILL BE POSSIBLE WITH THIS
ENVIRONMENT.
..GARNER/MOSIER.. 06/20/2013
