SPC AC 091232

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0732 AM CDT Tue Aug 09 2022

   Valid 091300Z - 101200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
   MID-ATLANTIC INTO SOUTHERN NEW ENGLAND AND ACROSS PORTIONS OF THE
   INTERIOR PACIFIC NORTHWEST...

   ...SUMMARY...
   Thunderstorms associated with marginally severe wind gusts will be
   possible today from the Mid-Atlantic into southern New England.
   Other storms with potential for strong wind gusts will be possible
   in parts of the Interior Pacific Northwest.

   ... Synopsis ...

   An expansive mid-level anticyclone, centered over the central
   Rockies, continues to be the dominant synoptic-scale feature for the
   contiguous United States. This mid-level anticyclone will build
   northward into southwest Canada today in response to a mid-level
   cyclone moving northward along the California and Oregon coasts.
   Additionally, a weak short-wave trough will move across northern New
   England and out over the Atlantic.

   At the surface, a weak cold front stretching from the Northeast into
   the southern High Plains will continue to slowly move
   south-southeast today. This cold front will serve as the focus of
   scattered thunderstorms this afternoon along much of its extent.

   ... Mid-Atlantic to Southern New England ...

   As the mid-level trough departs northern New England, a surface cold
   front will push southward toward the coast. Ahead of this front,
   surface dewpoints in the upper 60s F and low 70s F will contribute
   to a narrow corridor of instability, with most-unstable CAPE around
   1000-1500 J/kg by late morning and early afternoon. Thunderstorms
   will develop along and ahead of the surface front by late morning.
   Deep-layer shear should remain too weak for synoptically driven
   thunderstorm organization, but steep low-level lapse rates and
   precipitable water around two inches will support a marginal
   wind-damage threat with the strongest multicell clusters. The threat
   should end later this evening as the surface front moves through.

   ... Interior Pacific Northwest ...

   As the mid-upper low moves northward along the California and Oregon
   coats, deep-tropospheric southerly flow will be maintained across
   northern California and central Oregon. This will establish and
   maintain a corridor of maximized tropospheric moisture and
   corresponding instability from western Nevada into central Oregon.
   Multiple rounds of thunderstorms will be possible across this area,
   beginning as early as midday. Given the strength of the mid-level
   flow and the potential for steep low-level-lapse rates -- nearly dry
   adiabatic -- a few marginally severe downdrafts will be possible
   into the evening.

   ..Marsh/Edwards.. 08/09/2022

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