SPC 1630Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1119 AM CDT Mon Aug 02 2021

Valid 021630Z - 031200Z


Strong to isolated severe downburst winds will be possible over
central Oregon this afternoon and early evening.

Upper ridging is expected to persist across the western CONUS
through the day while mid-level troughing/broad cyclonic flow will
prevail across the central and eastern U.S. At the base of the
mid-level eastern trough, scattered to numerous thunderstorms are
already underway across the south-central/southeast U.S. With
continued surface heating, more widespread thunderstorm development
is expected through the afternoon. Similarly across the Interior
West, scattered to numerous thunderstorms are expected to develop
with increasing buoyancy given the presence of ample monsoonal
moisture. In central Oregon, high-based thunderstorm development is
expected atop a deep, dry boundary layer later this afternoon and
evening. A few of the stronger storms may be accompanied by strong,
gusty winds.

...Central Oregon...
The latest guidance consensus (including high-resolution
deterministic and ensemble members) continue to show pulse updraft
and occasional multicellular cluster development by early afternoon
atop the southern Cascades. These storms will form along the western
periphery of the upper ridge, amid 25-35 kt southwesterly mid-level
flow. The latest guidance continues to portray inverted-v vertical
thermodynamic profiles across the region as the dry boundary layer
is expected to mix up to 600-500 mb. Given 0.75-1.0 inch
precipitable water values and 9.5 C/km 0-3km lapse rates driven by
the deeply mixed boundary layer, adequate evaporative cooling may
take place to support a few damaging gusts, prompting the
continuation of the Marginal Risk.  

...Southeast U.S...
Scattered to numerous thunderstorms are developing in proximity to
and ahead of an MCV over MS. With continued heating along a diffuse
baroclinic zone across the Southeast, more widespread thunderstorm
development is likely in advance of the MCV. Given very weak
troposheric flow and associated vertical wind shear across the
region, convection is expected to remain generally pulse-cellular in
nature, with some clustering/chaotic cold pool mergers likely. Given
the presence of 2000-3000 J/kg MLCAPE (driven primarily by deep
low-level moisture), a couple of wet downbursts/damaging gusts are
possible. However, the damaging gust threat still appears too
sparse/disorganized to support the addition of a Marginal Risk.

..Squitieri/Mosier.. 08/02/2021

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