Thursday, June 25, 2020

SPC Jun 25, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook
Day 3 Outlook Image
Day 3 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
0227 AM CDT Thu Jun 25 2020

Valid 271200Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OHIO
ACROSS PENNSYLVANIA AND PARTS OF SOUTHERN NEW YORK...

CORRECTED GRAPHICS

...SUMMARY...
Scattered afternoon thunderstorms may pose a risk for mainly
damaging winds across much of Pennsylvania and portions of
surrounding states on Saturday.

...Synopsis...
As a mid-level short-wave trough shifts out of the Midwest and
across the central Appalachians region, a larger trough is forecast
to dig southeastward across the northwestern U.S. through the
period.

At the surface, a cold front will progress southward and eastward
across the northwestern quarter of the country, with some degree of
severe potential likely evolving over portions of the northern
Intermountain region/northern High Plains.  A weak cool front will
also cross Pennsylvania/New York and vicinity, and will also be
accompanied by risk for locally severe storms.

...Eastern Ohio across Pennsylvania and southern New York...
Some uncertainty still exists with respect severe potential across
the central Appalachians region, given the likelihood for ongoing
convection at the start of the period which would influence
potential for subsequent afternoon destabilization.  Still, with
moderately strong west-southwesterly flow aloft across the region
ahead of the weak upper trough/cool front, any uptick in afternoon
convective coverage would likely be accompanied by risk for damaging
winds given fast-moving storms.  A SLGT/level 2 risk area is being
introduced across the area given what appears to be reasonable
potential for locally damaging wind gusts, with threat likely to
peak during the late afternoon before waning into the evening hours.

...Portions of Idaho northeastward across parts of Montana...
Cooling aloft with the approach of upper troughing, combined with
diurnal heating, will permit modest destabilization to occur across
the northern Intermountain region through the afternoon.  As this
occurs, isolated storm development is expected along an advancing
cold front, primarily from southeastern Idaho northeastward into
central Montana.  Meager low-level moisture will likely be a
limiting factor with respect to ample destabilization for a more
widespread/substantial severe risk, but isolated gusty/damaging
winds will be possible --- aided by the deep mixed layer and
associated potential for evaporatively augmented downdrafts.  Risk
may continue well into the evening, as storms spread eastward toward
eastern Montana.

..Goss.. 06/25/2020

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day3otlk_0730.html

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