SPC AC 021729

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1229 PM CDT Sat Jun 02 2018

   Valid 031200Z - 041200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY INTO
   SUNDAY NIGHT ACROSS PARTS OF THE SOUTHERN ROCKIES...SOUTHEAST AND
   NORTHERN INTERMOUNTAIN REGION...

   ...SUMMARY...
   A few strong to severe storms will be possible Sunday into Sunday
   night across parts of the southern Rockies and adjacent High Plains,
   the Southeast, and the interior Pacific Northwest.

   ...Synopsis...
   The stronger belt of mid-latitude westerlies emanating from the
   Pacific may remain more or less zonal through this period, but with
   broad troughing beginning to develop inland of the Pacific coast,
   while broad downstream ridging continues to shift eastward, across
   and east of the Canadian Prairies and northern U.S. Rockies. 
   Farther east, a significant short wave trough is forecast to
   progress across the Great Lakes region,  while ridging in the
   northern branch of split downstream flow shifts into New England,
   and troughing within the southern branch shifts off the middle and
   southern Atlantic coast.  A subtropical high, elongated along an
   axis across southern Baja into the southern U.S. Plains, appears
   likely to remain prominent, but a substantive impulse is forecast to
   continue migrating around its northwestern/northern periphery,
   across the Four Corners vicinity toward the central High Plains.

   In lower levels, models suggest that significant surface
   cyclogenesis is possible northeast of the upper Great Lakes region,
   while much more modest cyclogenesis takes place off the southern Mid
   Atlantic coast.  Sharp low-level cooling/drying with the former
   feature is expected to continue an eastward/southward surge, across
   the Appalachians into the Atlantic Seaboard, and through the Gulf
   States, while stalling along the western slopes of the southern
   Rockies.  At least some initial subsidence/drying may be ongoing at
   the outset of the period to the lee of the southern Appalachians in
   association with the latter feature, while cool/stable boundary
   layer air gradually advances southward to the lee of the central
   Appalachians.

   ...Southeast...
   Convective potential for Sunday remains unclear.  Ahead of the
   southeastward advancing front, lower/mid tropospheric flow may be
   only modest in strength and largely west/northwesterly, with
   low-level convergence remaining generally weak.  However, beneath a
   remnant plume of elevated mixed layer air suppressed to the south of
   the stronger mid-latitude westerlies, low-level moisture is expected
   to remain sufficient to contribute to large CAPE (2000-3000+ J/kg)
   with daytime heating.  Guidance is suggestive that one or more
   subtle perturbations within the northwesterly flow aloft (perhaps
   convective generated) may suppress inhibition sufficiently to
   support scattered afternoon/evening thunderstorm activity,
   particularly across parts of southern Alabama and Georgia into
   northern Florida.  Given the potential instability, some of this may
   be accompanied by a marginal severe wind/hail risk.

   ...New Mexico/Southwest Texas...
   Models indicate appreciable destabilization is possible Sunday in
   the presence of steep lapse rates, mainly across the higher terrain
   to the west of the Rio Grande River in New Mexico, and perhaps into
   the Sacramento/Guadalupe/Davis Mountains vicinity of southern New
   Mexico into southwest Texas.  It appears that this will occur in the
   presence of strengthening southwesterly 500 mb flow (30-50
   kt--associated with impulse migrating around the subtropical ridge),
   which could provide sufficient vertical shear for isolated
   supercells with a severe hail/wind threat before diminishing Sunday
   evening.

   Cooler/drier low-level air initially advecting into the southern
   High Plains may be problematic to vigorous convective development
   with severe weather potential spreading east of the southern Rockies
   Sunday evening.

   ...Northern intermountain region...
   Models indicate that a vigorous short wave impulse progressing
   inland of the Pacific coast will probably be accompanied by
   sufficient forcing for ascent and strengthening shear to support a
   risk for severe storm development, including supercells, given
   sufficient destabilization Sunday afternoon and evening.  This
   remains unclear at this time, but at least weak destabilization
   appears possible across the higher terrain of northeast Oregon into
   western Montana.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:  <2%     - None
   Wind:      5%     - Marginal
   Hail:      5%     - Marginal

   ..Kerr.. 06/02/2018

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