SPC AC 141749

   DAY 2 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   1249 PM CDT THU MAY 14 2015

   VALID 151200Z - 161200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS FRIDAY AFTERNOON AND EVENING
   ACROSS PARTS OF WESTERN AND CENTRAL NEBRASKA...ADJACENT SOUTHEASTERN
   WYOMING AND SOUTHERN SOUTH DAKOTA...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SURROUNDING AREAS OF THE
   CENTRAL PLAINS...

   ...THERE IS A MRGL RISK OF SVR TSTMS EASTWARD ACROSS THE MIDDLE
   MISSISSIPPI VALLEY INTO SOUTHERN PORTIONS OF THE GREAT LAKES
   REGION...AND SOUTHWARD THROUGH THE REMAINDER OF THE SOUTHERN HIGH
   PLAINS...

   CORRECTED FOR A FEW TYPOS/WORDING

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE EXPECTED ACROSS PARTS OF THE NORTH CENTRAL
   HIGH PLAINS FRIDAY AFTERNOON AND EVENING.  MORE ISOLATED SEVERE
   STORM DEVELOPMENT IS POSSIBLE SOUTHWARD INTO THE SOUTHERN HIGH
   PLAINS BY FRIDAY EVENING.  OTHER SCATTERED STRONG TO SEVERE STORMS
   ARE POSSIBLE FRIDAY ACROSS PARTS OF THE MIDDLE MISSISSIPPI VALLEY
   INTO SOUTHERN PORTIONS OF THE GREAT LAKES REGION.

   ...SYNOPSIS...
   A SPLIT IN THE MID-LATITUDE WESTERLIES WILL PERSIST ACROSS THE
   NORTHEASTERN PACIFIC THROUGH THIS PERIOD...WITH MODELS SUGGESTING AN
   UPPER HIGH CENTER BECOMING INCREASINGLY PROMINENT OVER NORTHERN
   BRITISH COLUMBIA AND THE YUKON TERRITORY.  WITHIN THE SOUTHERN
   STREAM...TO THE SOUTH OF THE RIDGE...CYCLONIC MID/UPPER FLOW MAY
   BROADEN ACROSS PARTS OF THE EASTERN PACIFIC THROUGH MUCH OF THE U.S.
   PLAINS BY 12Z SATURDAY.  ONE OF THE MORE SIGNIFICANT EMBEDDED SHORT
   WAVE IMPULSES APPEARS LIKELY TO GRADUALLY PIVOT FROM THE EASTERN
   GREAT BASIN THROUGH THE NORTHERN HIGH PLAINS FRIDAY THROUGH FRIDAY
   NIGHT.  AT THE SAME TIME...THE PRIMARY/STRONGER
   PERTURBATION...COMING INCREASINGLY IN PHASE WITH THE SUBTROPICAL
   STREAM...IS EXPECTED TO PROGRESS INLAND ACROSS SOUTHERN
   CALIFORNIA/NORTHERN BAJA DURING THE DAY...BEFORE CONTINUING EAST OF
   THE LOWER COLORADO VALLEY...TOWARD THE SOUTHERN ROCKIES...FRIDAY
   NIGHT.  AROUND THE NORTHERN PERIPHERY OF DOWNSTREAM AMPLIFYING
   LARGE-SCALE RIDGING...ANOTHER SUBSTANTIVE SHORT WAVE TROUGH PROBABLY
   WILL TRACK FROM THE GREAT LAKES REGION THROUGH MUCH OF THE
   NORTHEAST.

   IN LOWER-LEVELS...A SURFACE FRONTAL ZONE APPEARS LIKELY TO TEND TO
   SHIFT NORTHWARD ACROSS THE NORTHERN TIER STATES...TO THE EAST OF THE
   ROCKIES...MORE RAPIDLY THROUGH THE NORTHERN PLAINS AND UPPER MIDWEST
   THAN THE LOWER GREAT LAKES REGION.  SURFACE TROUGHING WILL PROBABLY
   CONTINUE TO DEEPEN TO THE LEE OF THE ROCKIES...WITH MODELS
   INDICATING A CONSOLIDATING/DEEPENING LOW CENTER OVER THE NORTHERN
   HIGH PLAINS BY THE END OF THE FORECAST PERIOD.  EAST OF THE SURFACE
   TROUGH...AND ALONG/SOUTH OF THE FRONT...LOWER LEVELS ARE EXPECTED TO
   CONTINUE TO MOISTEN ON SOUTHERLY FLOW.

   BY LATE FRIDAY AFTERNOON...INSOLATION IS EXPECTED TO BE SUFFICIENT
   TO SUPPORT CORRIDORS OF MODEST BOUNDARY LAYER DESTABILIZATION
   /CHARACTERIZED BY CAPE OF 1000-2000 J PER KG/ ACROSS PARTS OF THE
   HIGH PLAINS...AND ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI VALLEY
   THROUGH SOUTHERN PORTIONS OF THE GREAT LAKES REGION. 
   MEANWHILE...STRONGEST VERTICAL SHEAR SHOULD BECOME FOCUSED ACROSS
   THE NORTH CENTRAL HIGH PLAINS.  HOWEVER...MODEST WESTERLY DEEP LAYER
   FLOW/SHEAR MAY DEVELOP WITH THE UPPER IMPULSE...NEAR THE
   FRONT...ACROSS THE SOUTHERN GREAT LAKES REGION...PERHAPS ALSO WITH
   ANOTHER WEAK IMPULSE CROSSING THE MIDDLE MISSISSIPPI VALLEY.

   ...HIGH PLAINS...
   MOISTENING EASTERLY/SOUTHEASTERLY LOW-LEVEL UPSLOPE FLOW...TO THE
   NORTHEAST OF A DAYTIME SURFACE LOW CENTER OVER NORTHEAST
   COLORADO...IS EXPECTED TO HELP FOCUS PRIMARY STORM DEVELOPMENT
   ACROSS THE NORTH CENTRAL HIGH PLAINS FRIDAY AFTERNOON.  THIS SHOULD
   BE AIDED BY MID/UPPER FORCING ASSOCIATED WITH THE LEAD IMPULSE
   MIGRATING OUT OF THE EASTERN GREAT BASIN...WHICH COULD CONTRIBUTE TO
   THE INITIATION OF VIGOROUS STORMS ACROSS PARTS OF NORTHEAST
   COLORADO/SOUTHEAST WYOMING AS EARLY AS MIDDAY.  ACTIVITY SHOULD THEN
   DEVELOP/SPREAD NORTHWARD/NORTH NORTHEASTWARD THROUGH MUCH OF WESTERN
   AND CENTRAL NEBRASKA AND SOUTHERN SOUTH DAKOTA THROUGH THE REMAINDER
   OF THE AFTERNOON AND EVENING HOURS. IN THE PRESENCE OF STRONG DEEP
   LAYER SHEAR...AND SIZABLE CLOCKWISE CURVED LOW-LEVEL
   HODOGRAPHS...ORGANIZED CONVECTION...INCLUDING SUPERCELLS...WILL
   SUPPORT THE RISK FOR SEVERE HAIL AND A FEW TORNADOES
   INITIALLY...BEFORE THE RISK OF DAMAGING WIND GUSTS BECOMES MORE
   PROMINENT FRIDAY EVENING.

   ISOLATED SUPERCELLS MAY ALSO NOT BE OUT OF THE QUESTION ALONG THE
   DRYLINE SOUTHWARD THROUGH THE CENTRAL AND SOUTHERN HIGH PLAINS LATE
   FRIDAY AFTERNOON AND EVENING.  BUT PRIMARY THUNDERSTORM DEVELOPMENT
   MAY AWAIT FORCING WITH THE STRONGER UPSTREAM IMPULSE...WHICH MAY NOT
   OCCUR UNTIL LATE FRIDAY NIGHT.

   ..KERR.. 05/14/2015

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