Convective Outlook

Days 4 - 8 Storm Prediction Center Norman, Oklahoma

ACUS48 KWNS 210954
SWOD48
SPC AC 210953

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0353 AM CST Thu Feb 21 2019

Valid 241200Z - 011200Z

...DISCUSSION...
The center of a broad and deep cyclone may begin to weaken while
migrating north of the Great Lakes region on Sunday, but models
suggest that significant secondary cyclogenesis is possible from the
vicinity of the New England coast through the Canadian Maritimes.
Ahead of a trailing cold front, which is expected to advance east of
the Appalachians, and across the mid and south Atlantic Seaboard,
models suggest that low-level moistening may support sufficient
destabilization to support one or more narrow lines of low-topped
convection, particularly across the Carolinas and Georgia.  However,
the extent to which thermodynamic profiles remain conducive to
lightning on Sunday is still unclear.  While severe thunderstorm
potential seems low, given the forecast strength of the
environmental wind fields (likely including 40-70 kt in the 850-700
mb layer), downward transport of momentum may result in localized
potentially damaging wind gusts even in showers.

Otherwise, medium-range models indicate that a blocking upper high
will evolve across the Gulf of Alaska into the Alaska/Yukon
vicinity, and remain prominent through this period.  This will
generally maintain broadly confluent flow downstream, inland of the
Pacific coast, though there may be some building of southern stream
ridging along the Pacific coast by late week, and downstream trough
amplification across the lower Rio Grande Valley.  At the same time,
the northern stream may remain broadly cyclonic across the Canadian
Prairies through the Upper Midwest and Northeast.  This regime
appears likely to maintain cold surface ridging from the lee of the
Rockies across and east of the Mississippi Valley through much of
the period, contributing to the maintenance of low severe weather
potential.

..Kerr.. 02/21/2019