July 19 Severe Weather Discussion- Conditional Storm Action Day Declared

Today's Severe Weather Threat

Today's Hail Outlook

Today's Tornado Outlook

Today's High Wind Threat

A Conditional Storm Action Day has been declared because today's severe threat covers such a large area.

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN ROCKIES EWD INTO
   THE UPPER GREAT LAKES AND SEWD INTO THE CNTRL APPALACHIANS TO MID
   ATLANTIC COAST...
   
   ...NRN ROCKIES EWD ACROSS MT...
   
   POTENT SHORT WAVE TROUGH AND ATTENDING 50-60 KT MIDLEVEL JET STREAK
   WILL PROGRESS NEWD ACROSS THE REGION DURING THE D1 PERIOD ALONG WITH
   ACCOMPANYING PACIFIC FRONT.  STEEP MIDLEVEL LAPSE RATES ATOP
   BOUNDARY LAYER DEWPOINTS IN THE 50S WILL YIELD A MODERATELY UNSTABLE
   AIR MASS BY AFTERNOON WITH MLCAPE INCREASING TO 1000-1500 J/KG. 
   TSTMS WILL INCREASE IN COVERAGE AND INTENSITY THIS AFTERNOON AND
   TONIGHT INVOF SURFACE FRONT AND FAVORED TERRAIN AS LARGE-SCALE
   FORCING ASSOCIATED WITH MIDLEVEL TROUGH OVERSPREADS DESTABILIZING
   AIR MASS.  VERTICALLY VEERING WIND PROFILES ACROSS WARM SECTOR WILL
   FAVOR THE DEVELOPMENT OF SUPERCELLS IN ADDITION TO BOWING STRUCTURES
   WITH A RISK FOR MAINLY DAMAGING WINDS AND HAIL SPREADING EWD INTO
   THE NRN HIGH PLAINS TONIGHT.
   
   ...NRN PLAINS INTO UPPER GREAT LAKES AND MIDWEST...
   
   WHILE MIDLEVEL HEIGHTS WILL BEGIN TO LOWER OVER THE DAKOTAS DURING
   THE LATTER HALF OF THE FORECAST PERIOD...LARGE-SCALE FORCING FOR
   ASCENT WILL REMAIN NEGLIGIBLE FARTHER E/SE.  IN THE LOW
   LEVELS...WEAK SURFACE LOW OBSERVED OVER N-CNTRL SD MAY PERSIST
   THROUGH THE DAY ALONG SURFACE BOUNDARY WHICH WILL RETREAT NWD AS A
   WARM FRONT IN RESPONSE TO DEEPENING LEE CYCLONE PROGRESSING THROUGH
   CNTRL/ERN MT.
   
   CLUSTERS OF MAINLY ELEVATED TSTMS ARE ONGOING ACROSS PORTIONS OF ERN
   ND/NRN MN...DRIVEN BY WAA TO THE N/NE OF SURFACE FRONT AND WITHIN
   EXIT REGION OF SWLY LLJ.  HAIL AND LOCALLY DAMAGING WIND GUSTS WILL
   BE POSSIBLE WITH THESE STORMS THROUGH MID MORNING BEFORE ACTIVITY
   WEAKENS WITH THE DIURNAL CESSATION OF LLJ.  THEREAFTER...TSTM
   DEVELOPMENT AND EVOLUTION BECOMES MUCH MORE UNCERTAIN OWING TO THE
   WEAKLY FORCED ENVIRONMENT.  CURRENT INDICATIONS ARE THAT SEGMENT OF
   SURFACE BAROCLINIC ZONE EXTENDING FROM THE WRN DAKOTAS INTO MN HAS
   THE HIGHEST PROBABILITY OF EXPERIENCING SEVERE STORMS THIS AFTERNOON
   INTO TONIGHT.  INCREASING HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT
   WILL BE THE PRIMARY FORCING MECHANISM LATER TODAY ACROSS WRN ND WITH
   INCREASING LOW-LEVEL WAA AT TERMINUS OF DEVELOPING 30-40 KT LLJ THE
   MAIN FOCUS FOR STORMS FARTHER E.
   
   AMBIENT ENVIRONMENT INVOF WARM FRONT WILL BE CHARACTERIZED BY A VERY
   MOIST BOUNDARY LAYER BENEATH STEEP MIDLEVEL LAPSE RATES...YIELDING
   MLCAPE VALUES 2500-5000 J/KG.  DEEP-LAYER VERTICAL SHEAR WILL NOT BE
   PARTICULARLY STRONG /I.E. LESS THAN 35 KT/...HOWEVER VERTICALLY
   VEERING WINDS INVOF SURFACE BOUNDARY WILL SUPPORT ORGANIZED STORM
   STRUCTURES CAPABLE OF LARGE HAIL...DAMAGING WINDS AND PERHAPS A
   TORNADO.
   
   ...OH VALLEY INTO THE CNTRL APPALACHIANS AND MID ATLANTIC COAST...
   
   WEAK MIDLEVEL PERTURBATIONS /SOME OF CONVECTIVE ORIGIN/ WILL
   PROGRESS SEWD ACROSS REGION TODAY WITHIN DIFFLUENT MIDLEVEL FLOW
   REGIME.  IN THE LOW LEVELS...A SWD-MOVING COLD FRONT AND EXISTING
   OUTFLOW BOUNDARIES WILL SERVE AS THE FOCI FOR DIURNAL TSTM
   DEVELOPMENT...SOME OF WHICH COULD BE SEVERE.
   
   TSTMS ONGOING ACROSS SRN OH INTO WV MAY WEAKEN THIS MORNING AS NWLY
   LLJ OVER THE OH VALLEY DIMINISHES.  RESIDUAL CLOUD DEBRIS MAY TEMPER
   DAYTIME HEATING AT SOME LOCATIONS...WHILE ELSEWHERE STRONGER
   INSOLATION COUPLED WITH A MOIST BOUNDARY LAYER WILL BE SUPPORTIVE OF
   AFTERNOON MLCAPE APPROACHING 1000-2000 J/KG.  VERTICAL SHEAR WILL
   REMAIN RATHER WEAK...THOUGH THE MODERATE INSTABILITY...STEEPENING
   LOW-LEVEL LAPSE RATES AND RELATIVELY MOIST ENVIRONMENT SUGGEST THE
   POTENTIAL FOR STRONG WET MICROBURSTS AND AN ATTENDANT DAMAGING WIND
   THREAT.