SPC AC 171956

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0256 PM CDT Fri May 17 2019

   Valid 172000Z - 181200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION
   OF NEBRASKA AND WEST TEXAS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF
   THE CENTRAL AND SOUTHERN PLAINS AS WELL AS THE OHIO VALLEY THROUGH
   MIDDLE ATLANTIC REGION...

   ...SUMMARY...
   Severe storms with very large hail, damaging winds, and a few
   tornadoes (a couple of which could be strong) are expected over
   Nebraska and adjacent regions this afternoon and evening.  A few
   severe storms capable of very large hail and damaging winds will
   also affect portions of western Texas.  Finally, scattered afternoon
   storms capable of locally gusty/damaging winds will be possible from
   Ohio through the Middle Atlantic region.

   ...Discussion...

   Only modest adjustments have been made to previous forecast which
   still appears mostly on track. Primary area of severe storms this
   afternoon and early evening is expected to evolve across NE where
   discrete storms will likely develop near surface low at intersection
   of the front and dryline and subsequently spread northeast through
   the destabilizing warm sector where MLCAPE is already near 2500
   J/kg. Vertical shear from 40-45 kt will support supercells with very
   large hail. Tornado threat will also increase by late afternoon into
   the early evening as the low-level jet and 0-1 km hodograph size
   increase.

   More isolated supercells remain possible with southward extent along
   the dryline this afternoon and evening. Numerous storms (some of
   which will likely become severe) are expected across west through
   northwest TX later tonight as the Pacific cold front intercepts the
   dryline.

   ..Dial.. 05/17/2019

   .PREV DISCUSSION... /ISSUED 1108 AM CDT Fri May 17 2019/

   ...NE and vicinity...
   Morning water vapor loop shows a powerful upper trough digging
   across the Great Basin into the Rockies.  Midlevel height falls and
   wind speeds are increasing over the High Plains, where multiple
   clusters of severe thunderstorms are forecast for this afternoon and
   tonight.  One area of concern will be over parts of eastern CO/WY,
   northern KS, much of NE, and southern SD.  Storms are expected to
   initiate by late afternoon over northeast CO into southwest NE and
   northwest KS, with forecast hodographs favoring supercell storm
   modes.  Steep midlevel lapse rates and ample CAPE will encourage
   hail production, with very large hail possible.  The corridor of
   greatest tornado threat is forecast to extend across central and
   northern NE as storms track north-northeastward across a moist and
   moderately unstable warm sector.  Intense storms should eventually
   move into parts of SD where they may become elevated, but remain
   capable of large hail.

   ...Southwest TX...
   A very moist and unstable air mass is in place today over parts of
   southwest TX, with dewpoints in the upper 60s extending from Del Rio
   to Abilene, TX.  A few intense storms are expected to form in this
   region this afternoon, but should remain rather isolated.  These
   storms will pose a risk of very large hail and perhaps a tornado. 
   More widespread convection will develop after dark across the
   SLGT/ENH risk area.  These storms will maintain organization through
   the overnight period and spread toward northwest TX and southwest
   OK, posing a risk of large hail and damaging winds.

   ...Mid Atlantic States...
   Pockets of strong heating and sufficient CAPE will lead to scattered
   thunderstorm development over parts of OH/WV this afternoon. 
   Moderately strong west-northwest flow aloft will help to organize
   these storms and spread them toward parts of VA.  Confidence in an
   organized severe threat in this area is not particularly high, but
   there is a risk of gusty/damaging winds in the strongest cells this
   afternoon and evening.

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