SPC 0600Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1200 AM CDT Tue May 04 2021

Valid 051200Z - 061200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS WEDNESDAY ACROSS
NORTHEASTERN GULF COASTAL AREAS INTO THE SOUTHERN MID ATLANTIC COAST
REGION...

...SUMMARY...
Strong thunderstorms may impact northeastern Gulf coastal areas
early Wednesday, with additional strong storms possible across parts
of the southern Mid Atlantic coast region during the day.  A few of
these storms may pose at least some risk for severe hail and
potentially damaging wind gusts.

...Synopsis...
Models indicate that the leading edge of an amplified belt of 
westerlies emanating from the northern mid-latitude Pacific will
gradually continue to develop inland across the Pacific
Northwest/British Columbia coast, Wednesday through Wednesday night.
 This likely will include a mid-level ridging, which probably will
begin to sharpen as it shifts into the northern U.S. intermountain
region and Canadian Rockies vicinity.  It appears that blocking may
become at least a bit more prominent in the downstream flow,
centered near the Labrador Sea, and a broadening mid-level low
centered near James Bay may move little through this period.  South
of this feature,  models indicate that a more prominent cyclonic
mid-level flow will continue to evolve across the Mississippi Valley
through the Atlantic Seaboard.  This is forecast to occur as at
least a couple of short wave perturbations dig to the lee of the
upstream ridging, and remnant perturbations, emerging in prior days
from the Southwest, progress across the Atlantic Seaboard.

There now appears greater consensus among the various models that
one of these short waves may provide support for cyclogenesis within
pre-cold frontal surface troughing near the northern Mid Atlantic
coast by the beginning of the period.  It appears that this will
proceed across the southern New England coast vicinity into the
Atlantic Wednesday through Wednesday night, with the trailing cold
front advancing across the middle through southern Atlantic Coast
region, and into the northern Gulf of Mexico.

...Mid Atlantic through parts of the Southeast...
A large, composite pre-frontal convective outflow boundary may still
be a focus for vigorous thunderstorm activity at 12Z Wednesday,
across southern Louisiana/Mississippi and Alabama coastal areas into
parts of the Florida Panhandle and southern Georgia.  Although
deep-layer mean wind fields and shear may be in the process of
weakening, and becoming more marginal for organized thunderstorm
development, continuing inflow of seasonably moist air (supportive
of CAPE in excess of 1000 J/kg) may be sufficient to maintain at
least some risk for damaging wind gusts and perhaps some hail,
before activity advances offshore.

Stabilization of upstream lapse rates, associated with widespread
convective overturning Tuesday through Tuesday night, will be a
factor mitigating convective potential across the northeastern Gulf
coast vicinity, as well as across much of the southern into mid
Atlantic Seaboard.  Additionally, it now appears more probable that
early veering of flow to an increasingly westerly component, coupled
with mid-level subsidence and drying, will suppress convective
potential to the east of the southern Appalachians.  However, at
least some model output suggests that another short wave impulse
approaching the Appalachians during the day could provide support
thunderstorm development by late afternoon, particularly across the
North Carolina Piedmont.  A corridor of stronger pre-frontal heating
and residual low-level moisture may contribute to thermodynamic
profiles supportive of at least some risk for hail and damaging wind
gusts.  This will tend to spread eastward toward the southeast
Virginia/North Carolina coastal plain, beneath 40-50+ kt
west-southwesterly 500 mb flow.

..Kerr.. 05/04/2021

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