SPC 1730Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1212 PM CDT Sun Aug 01 2021

Valid 021200Z - 031200Z


The risk of severe thunderstorm appears negligible across the U.S.,
Monday through Monday night.

The most prominent short wave trough impacting the U.S. during this
period appears likely to accelerate east-northeast of New England by
early Monday.  This is expected to occur as an even stronger
upstream perturbation digs southeast of Hudson/James Bays, before
turning eastward across northern Quebec by Monday night.

While the stronger westerlies may begin to trend at least a bit more
zonal across eastern Canada, models indicate that larger-scale
mid/upper troughing will persist east of the Rockies through the
Atlantic Seaboard, within a much weaker flow regime across the
southern mid- and subtropical latitudes.  Some further amplification
of the troughing is possible across the Gulf Coast region, in
response to digging smaller-scale perturbations to the east of
large-scale ridging initially encompassing much of western North

Downstream of quasi-stationary troughing off the Pacific coast,
strongest mid-level level ridging appears likely to persist across
the lower Colorado Valley into the Great Basin.  To the north and
east of this axis, at least a couple of weak perturbations will
contribute to suppression of the ridging, while very slowly
continuing to progress through the broader anticyclonic regime.

...Rockies and areas to the west...
A plume of monsoonal moisture along and east of these perturbations
appears likely to provide the primary focus for diurnal thunderstorm
development across the Intermountain West and Rockies.  However,
there may be sufficient residual low-level moisture to the east of
the Oregon Cascades to support a few thunderstorms, and perhaps a
developing cluster of storms late Monday, aided by large-scale
forcing for ascent downstream of the offshore troughing.  While (as
is typically the case) there is potential for thermodynamic profiles
across each of these areas to become at least locally supportive of
isolated downbursts and/or perhaps marginally severe hail, the risk
for organized severe weather appears low and severe probabilities,
in general, still less than 5 percent.

...East of Rockies...
The leading edge of substantive low-level cooling and/or drying
appears likely to reach the Gulf and south Atlantic Coast states by
early Monday.  Some continuing southward progression toward the
northwest Gulf coast appears probable through early Tuesday, with
some northward return possible across the Carolinas.  

While daytime heating may contribute to sufficient CAPE to support
scattered vigorous thunderstorm development within the moist air
mass during the day, this heating is forecast to be more modest than
prior days.  With modest to weak lower/mid tropospheric lapse rates
a limiting factor, coupled with the generally weak flow and shear,
severe weather probabilities associated with the risk for downbursts
and damaging surface gusts still appears less than 5 percent at the
present time.

..Kerr.. 08/01/2021

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