Day 1 Severe Weather Outlook

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE WEST-CENTRAL DAKOTAS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EXTENDING ACROSS THE TENNESSEE VALLEY INTO THE MID-ATLANTIC COAST...

...SUMMARY...
INITIALLY SCATTERED SUPERCELLS AND THUNDERSTORM CLUSTERS WILL PRODUCE A THREAT FOR VERY LARGE TO GIANT HAIL, A FEW TORNADOES, AND DAMAGING WINDS ACROSS THE NORTHERN ROCKIES INTO THE HIGH PLAINS THIS AFTERNOON, GRADUALLY EVOLVING INTO AN MCS WITH WIDESPREAD DAMAGING WINDS LIKELY, SOME IN EXCESS OF 75-95 MPH. SCATTERED SEVERE THUNDERSTORMS PRODUCING MAINLY A DAMAGING WIND THREAT ARE FORECAST THROUGH THIS EVENING ACROSS THE TENNESSEE VALLEY INTO THE MID-ATLANTIC.

...NORTHERN ROCKIES INTO THE PLAINS...
MORNING WATER VAPOR IMAGERY SHOWS A LARGE UPPER LEVEL TROUGH GRADUALLY AMPLIFYING AS IT REMAINS CENTERED OVER COASTAL BRITISH COLOMBIA INTO THE PACIFIC NORTHWEST. THE TROUGH WILL SLOWLY PUSH EAST-SOUTHEASTWARD TODAY WHILE CONTINUING TO AMPLIFY ACROSS THE INTERIOR PACIFIC NORTHWEST AND ROCKIES. BY LATE THIS AFTERNOON AND EVENING, SOUTHWESTERLY 50-65KT 500MB FLOW WELL AHEAD OF THE TROUGH AXIS WILL OVERSPREAD INTO THE NORTHERN PLAINS. NOTABLY, RATHER STRONG UPPER-LEVEL DIVERGENCE WILL BE FAVORABLY POSITIONED OVERTOP THE NORTHERN HIGH PLAINS WHERE THE GREATEST SEVERE THREAT WILL BE. AT THE SURFACE, A LARGE OCCLUDED CYCLONE CENTERED ACROSS SOUTHERN CANADA WITH THE OCCLUDED FRONT EXTENDING INTO WYOMING SLOWLY SHIFTS EAST TODAY AND TONIGHT. AHEAD OF THE SURFACE FRONT, A 40-50KT SOUTHERLY LOW-LEVEL JET WILL REMAIN IN PLACE ALL DAY ACROSS THE NORTHERN PLAINS/DAKOTAS, ALLOWING FOR IMPRESSIVE MOISTURE TRANSPORT TO CONTINUE, EVENTUALLY YIELDING WIDESPREAD MID 60S TO LOW 70S DEWPOINTS. A LARGE CLEAR SLOT MOVING OVERTOP THE REGION THIS MORNING WILL SUPPORT INTENSE DIURNAL HEATING INTO THE UPPER 80S AND 90S TODAY. IMPRESSIVE MID-LEVEL LAPSE RATES TO AROUND 9.0 C/KM WILL RESULT IN STRONG BUOYANCY BY THIS AFTERNOON WITH PEAK MLCAPE OF AROUND 3000-4000 J/KG. 

ISOLATED TO SCATTERED HIGH-BASED STORMS WILL INITIATE BY LATE THIS MORNING ACROSS THE CENTRAL ROCKIES, QUICKLY SPREADING NORTHEASTWARD INTO WYOMING AND SOUTHERN MONTANA. INTENSE DEEP-LAYER SHEAR ASSOCIATED WITH THE ADVANCING MID TO UPPER LEVEL JET WILL SUPPORT ORGANIZATION INTO BOTH SUPERCELLS AND LINEAR CLUSTERS, WITH VERY LARGE HAIL AND SCATTERED DAMAGING WINDS THE PRIMARY THREAT WITH THIS ACTIVITY. INCREASING FORCING FOR ASCENT BY MID-AFTERNOON WILL EVENTUALLY RESULT IN NUMEROUS THUNDERSTORMS RAPIDLY INITIATING ACROSS EASTERN MONTANA AND THE WESTERN DAKOTAS. FAIRLY LENGTHY, CURVED HODOGRAPHS WILL SUPPORT AN INITIAL SUPERCELL MODE WITH THIS ACTIVITY, WHICH WILL YIELD SCATTERED LARGE HAIL WITH DIAMETERS IN THE 2-4 INCH RANGE QUITE PROBABLE IN MORE PROMINENT UPDRAFTS. A FEW TORNADOES ARE ALSO POSSIBLE GIVEN FAVORABLE LOW-LEVEL HELICITY. 

BY EARLY THIS EVENING, CLUSTERING AND UPSCALE GROWTH SHOULD OCCUR FAIRLY QUICKLY NEAR THE BLACK HILLS REGION OF SOUTH DAKOTA, YIELDING A RAPIDLY INTENSIFYING BOWING MCS SPREADING NORTH-NORTHEAST THIS EVENING. INTENSIFYING DEEP-LAYER SHEAR TO OVER 50-60KT BY THIS POINT WILL BE MORE THAN FAVORABLE WITH THE IMPRESSIVE THERMODYNAMIC PROFILES TO SUPPORT SEVERAL DESTRUCTIVE GUSTS IN THE 75-95MPH RANGE WITH THE MCS AS IT BEGINS TO SURGE, WITH THE GREATEST POTENTIAL FOR INTENSE GUSTS ACROSS NORTHWEST SOUTH DAKOTA AND SOUTHWEST NORTH DAKOTA, WHERE A CATEGORICAL MODERATE (4/5) RISK HAS BEEN INTRODUCED. THE MCS WILL SPREAD NORTH NORTHEAST THROUGHOUT THE EVENING AND INTO THE OVERNIGHT HOURS CONTINUING TO PRODUCE WIDESPREAD DAMAGING WINDS OF 60-80MPH, ALONG WITH POTENTIAL FOR A FEW EMBEDDED TORNADOES.

FURTHER SOUTH ACROSS WESTERN NEBRASKA THIS AFTERNOON AND EVENING, WHILE A VERY FAVORABLE ENVIRONMENT, INCLUDING 3500-4500 J/KG MLCAPE AND ENLARGED HODOGRAPHS WILL EXIST, THE COMBINATION OF MODERATE CINH AND AT BEST A GLANCING BLOW FROM THE BETTER FORCING TO THE NORTH, UNCERTAINTY IS HIGH REGARDING THE COVERAGE OF STORMS. MULTIPLE CAMS AND RUNS HAVE CONSISTENTLY INDICATED A COUPLE OF WIDELY SCATTERED SUPERCELLS DEVELOPING OVER THE NEBRASKA PANHANDLE AND SPREADING EAST. THE INTENSE SRH OF 300-400 M2/S2 AND 50-60KT SHEAR OVERTOP THE STRONG BUOYANCY WOULD SUPPORT A THREAT FOR GIANT HAILSTONES AND PERHAPS A STRONG TORNADO WITH THIS ACTIVITY FOR A FEW HOURS BEFORE IT DISSIPATES LATE IN THE EVENING. 

...TENNESSEE VALLEY INTO THE MID-ATLANTIC...
A STALLED FRONT EXTENDS ACROSS THE TENNESSEE VALLEY INTO THE MID-ATLANTIC THIS MORNING WITH SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ONGOING AND SPREADING EAST NORTHEAST. WITH THIS ACTIVITY SLOWLY MOVING NORTH, THIS IS ALLOWING FOR A BROAD CORRIDOR OF FILTERED HEATING TO OCCUR. WITH A VERY MOIST AIRMASS, THIS SHOULD SUPPORT MLCAPE OF 2000+ J/KG TO DEVELOP BY EARLY AFTERNOON. RENEWED SCATTERED DEVELOPMENT SHOULD OCCUR AS THE AIRMASS DESTABILIZES, ALONG WITH A REMNANT MCV CURRENTLY OVER SOUTHWEST MO POTENTIALLY ENHANCING CONVECTIVE DEVELOPMENT. MODERATE DEEP-LAYER SHEAR OF 30-35KT WILL BE ENOUGH TO SUPPORT SCATTERED LOOSELY ORGANIZED CLUSTERS/LINE SEGMENTS SPREADING EAST, WITH PRIMARILY A THREAT FOR DAMAGING WIND GUSTS EXPECTED.

...LOWER MISSOURI VALLEY...
STRONG HEATING ACROSS THE REGION ALONG WITH DEWPOINTS INCREASING INTO THE MID TO UPPER 70S WILL SUPPORT 4000-5000 J/KG MLCAPE BY LATE THIS AFTERNOON. FAIRLY NEUTRAL HEIGHTS WITH OCCASIONAL SUBTLE HEIGHT RISES WILL LIMIT FORCING AS WELL AS EROSION OF STRONG CINH THIS AFTERNOON. BY EARLY EVENING HOWEVER, RATHER NEBULOUS FORCING COULD OCCUR WITH WEAK VORTICITY ADVECTION, AND THIS MAY BE ENOUGH TO ALLOW FOR A COUPLE OF STORMS TO ERUPT NEAR A LIFTING WARM FRONT. THIS HAS BEEN SUPPORTED BY SOME CAMS THOUGH THE OVERALL SIGNAL IS WEAK. SHOULD THIS DEVELOPMENT OCCUR, HOWEVER, THE VERY IMPRESSIVE KINEMATICS, INCLUDING LARGE CURVING HODOGRAPHS WOULD SUPPORT A SUPERCELL OR TWO TO QUICKLY EVOLVE AND IT COULD BE ASSOCIATED WITH A STRONG TORNADO THREAT. GIVEN THAT THERE IS A WEAK SIGNAL INVOLVED, LOW-END TORNADO PROBABILITIES ALONG WITH A CIG1 OUTLINE WERE MADE.

OVERNIGHT TONIGHT, INCREASING MOISTURE ADVECTION NORTH OF THE LIFTING FRONT AS WELL AS INCREASING FORCING POSSIBLY DRIVEN BY OVERRUNNING LOW-LEVEL JET WINDS MAY SUPPORT SCATTERED ELEVATED CONVECTION TO DEVELOP, WHICH WOULD BE ASSOCIATED WITH AN OCCASIONALLY SEVERE HAIL CORE.

...SOUTHERN HIGH PLAINS...
VERY WEAK FORCING DESPITE STRONG HEATING AND INSTABILITY ACROSS THE SOUTHERN HIGH PLAINS ALSO CASTS DOUBT ON CONVECTIVE INITIATION POTENTIAL. A WEAK SIGNAL FROM SOME CAMS EXISTS NONETHELESS, AND ANY STORM THAT DEVELOPS WOULD BE ASSOCIATED WITH A SEVERE DOWNBURST AND OUTFLOW WIND THREAT GIVEN A DEEPLY MIXED BOUNDARY LAYER AND MODERATE DEEP-LAYER SHEAR. LOW-END PROBABILITIES ARE MADE GIVEN THE FAVORABLE ENVIRONMENT AND WEAK CI SIGNAL.