SPC AC 181718
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1218 PM CDT Thu Oct 18 2018
Valid 191200Z - 201200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for severe thunderstorms appears negligible across the U.S.
Friday through Friday night.
Within a belt of westerlies emanating from the mid-latitude Pacific,
models indicate considerable amplification across the Pacific coast
through eastern Canada and the U.S. during this period. It appears
that this will include a building large-scale ridge across parts of
the northeast Pacific through the northern U.S. intermountain region
and Rockies, into the Canadian Prairies, with larger-scale troughing
evolving downstream, across the upper Mississippi and Ohio Valleys,
Great Lakes and Ontario/Quebec by 12Z Saturday.
Perhaps most prominent within the evolving cyclonic mid-level
regime, models indicate that a vigorous short wave trough emerging
from the Arctic latitudes will dig across Manitoba and northwestern
Ontario into the Upper Midwest/upper Great Lakes region. This is
expected to be accompanied by a significant reinforcing cold
intrusion, in the wake of a deepening cyclone migrating across James
Bay into Quebec.
Farther south, seasonably cool and stable conditions are expected to
generally prevail across the northern into southern tier of the
U.S., in the wake of a prior cold front. Seasonably high moisture
content appears likely to be initially confined to one narrow plume
across and east of the south Atlantic coast, and another across the
Texas Gulf coast, beneath lingering subtropical ridging. However,
weak to modest southerly return flows are forecast to develop
near/east of the south Atlantic coast, and across parts of the
southern Plains into the Ozark Plateau/lower Mississippi Valley.
North/northeast of the mid/upper Texas coastal plain, associated
destabilization appears likely to remain rather weak, and based
above a residual near surface stable layer. Due to sizable spread
among the various model output, it remains unclear whether this will
become sufficient to support thunderstorm development. If it does,
forcing to support activity may primarily coincide with the onset of
mid-level height falls late Friday night across parts of
central/northeast Texas into the Mississippi Delta vicinity.
Otherwise, isolated to widely scattered thunderstorm activity also
appears possible in association with modest boundary layer
destabilization near mid/upper Texas coastal areas, and perhaps near
northeast Florida coastal areas. However, the risk for severe
storms appears negligible.
...MAXIMUM RISK BY HAZARD...
Tornado: <2% - None
Wind: <5% - None
Hail: <5% - None
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