SPC AC 041728

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Thu Jun 04 2020

   Valid 051200Z - 061200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR THE NORTHERN
   ROCKIES AND ADJACENT PLAINS...EASTERN WYOMING...THE LOWER MISSOURI
   VALLEY...AND THE MID-ATLANTIC STATES...

   ...SUMMARY...
   Strong to locally severe thunderstorms are possible Friday afternoon
   and evening across parts of the Northern Rockies and adjacent
   plains, eastern Wyoming, Mid-Atlantic states, and the lower Missouri
   Valley.

   ...Northern Rockies and adjacent plains...
   The mid to upper-level pattern is forecast to amplify on Friday
   across the western U.S.  A mid-level ridge will build over the
   central and northern High Plains to the east of an amplifying
   mid-level trough forecast to move from the eastern Pacific into the
   interior Pacific Northwest during the period.  The northern
   periphery of steep 700-500mb lapse rates associated with the
   mid-level ridge, will spread north into much of central ID and
   southwest and western MT.  Although large-scale forcing will likely
   remain weak with stronger forcing displaced farther west over
   western OR/WA, strong heating over the higher terrain will favor
   isolated thunderstorms developing by late afternoon. 
   Capping/appreciable MLCINH will limit storm coverage over the
   adjacent High Plains but the steep lapse rates and an elongated
   hodograph would favor a conditional strong/severe risk.

   ...Eastern WY and the western NE Panhandle...
   Isolated thunderstorms are possible by late afternoon/evening as
   moist southeasterly low-level flow intensifies towards 6pm MDT.  The
   aforementioned mid-level ridge will likely limit storm coverage to
   no more than a few storms near a surface pressure trough extending
   southward through eastern WY.  Forecast soundings indicate any
   sustained storm will reside within a corridor of strong effective
   shear (40-50 kt) with steep low to mid-level lapse rates.  Strong
   gusts and large hail may accompany the stronger cores before this
   activity weakens during the evening as it moves into an increasingly
   capped/cooling boundary layer during the evening.

   ...Mid-Atlantic states...
   A weak mid-level trough initially over the OH Valley Friday morning
   is expected to reach the central Appalachians by late afternoon. 
   One or more smaller-scale thunderstorm bands are forecast to develop
   over south-central PA into eastern WV/western VA during the
   afternoon.  Although weak mid-level lapse rates and modest
   west-southwesterly mid to high-level flow characterize the setup,
   strong heating during the day east of the terrain (temperatures
   approaching 90 deg F), may favor a few stronger multicells capable
   of a damaging-gust threat.  This activity will likely weaken during
   the evening.

   ...Lower MO Valley...
   A highly dependent mesoscale scenario is forecast across the lower
   MO Valley on Friday.  Outflow from decayed convection from overnight
   Thursday/early Friday morning will likely become draped across the
   northern half of MO.  Strong heating to the west and south of the
   boundary will serve to weaken convective inhibition.  Less certain
   is the low coverage/evolution of possible storms within a strong
   unstable air mass.  Multicells capable of hail/wind will be the
   primary severe hazards.

   ..Smith.. 06/04/2020

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