SPC 1630Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1029 AM CST Sun Nov 15 2020

Valid 151630Z - 161200Z


Strong to severe wind gusts will remain possible with low-topped
showers and thunderstorms from the Lower Great Lakes to the
Northeast and Mid-Atlantic States through early tonight.

...Lower Great Lakes to Mid-Atlantic/Northeast...
Scattered thunderstorms are ongoing across southeast Lower MI into
western OH with a history of widespread strong to isolated severe
wind gusts. This initial activity may struggle to further intensify
owing to boundary-layer dew points in the lower 50s within a narrow
spatial corridor ahead of this convection. It should eventually
outpace this narrow wedge of surface-based instability as it spreads
east/north of Lake Erie later this afternoon.

A more pronounced squall line is expected to develop around 21-23Z
from central NY to central VA and sweep east-northeast across the
Northeast and New England coast through early tonight within an
intense shear/minimally buoyant environment. This squall should
develop as the robust cold front impinges on low-level moisture
advecting north from the Carolinas/South Atlantic Coast. Between
00-03Z, mid 50s boundary-layer dew points should reach as far north
as eastern PA into southern New England along the track of secondary
cyclogenesis. While low-level lapse rates will probably remain
weaker relative to the Lower Great Lakes region, the comparatively
richer low-level moisture should compensate. It is plausible that
lightning generation may be confined to areas farther north amid
scant elevated buoyancy and greater large-scale ascent.
Nevertheless, the presence of a low-topped squall line amid 50-60 kt
925-mb winds suggest strong to severe wind gusts are possible even
in the absence of lightning. As such, this region has been upgraded
to Slight Risk.

..Grams/Dean.. 11/15/2020

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