Day 4-8 Outlook

Day 4-8 Outlook Image

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0320 AM CST Fri Feb 19 2021

Valid 221200Z - 271200Z

Medium-range guidance indicates that initially suppressed mid-level
ridging, across the eastern mid-latitude Pacific into the U.S.
Pacific coast, may undergo considerable amplification next week,
roughly between 130-160 W longitude.  It appears that this may build
toward the Alaskan Arctic Circle vicinity, as a deep mid-level low
(initially centered to the north of Alaska, Yukon and the Canadian
Northwest Territories) shifts a bit southward and eastward across
north central Canada.  As this occurs, a mean west-northwesterly
mid-level flow regime, from the northeastern Pacific through the
U.S., may take on a much more substantive northerly component near
the Canadian/U.S. Pacific coast vicinity, into deepening troughing
across the Southwest by late next week.

Arctic surface air is expected to begin to surge southward to the
lee of the Canadian Rockies, but it may remain to the north of the
U.S. international border through at least this period.  However,
models suggest that it will be preceded by a southward surge of more
modestly cold air across much of the central and eastern U.S. by mid
to late next week.  With guidance indicating little potential for
significant surface cyclogenesis to the lee of the southern Rockies,
and boundary-layer moistening over the Gulf of Mexico slowed by
reinforcing subsidence and drying early next week, the risk for
severe thunderstorms appears low (i.e., less than 10 percent
probabilities) through at least next Friday.

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