- Day Three
acus03 kwns 270831
Storm Prediction Center ac 270830
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0230 am CST Friday Feb 27 2015
Valid 011200z - 021200z
..no severe thunderstorm areas forecast...
isolated to widely scattered thunderstorms will be possible across
coastal areas of central and Southern California. Scattered
thunderstorms will be possible from parts of East Texas to the
middle-south region of northern Mississippi...eastern Arkansas...and
In the large scale...a blocking ridge will remain in place generally
west of the Pacific coast...while split belts of downstream
westerlies continue to be broadly confluent along and east of The
Rockies.. this latter flow regime will be located between a
prominent subtropical ridge over the Bahamas/Caribbean to the Gulf
of Mexico and a persistent northeastern Canadian vortex.
A progressive northern-stream shortwave trough will track eastward from the
northern plains through the Great Lakes region on Sunday. Heights will
rise into The Four Corners region and across the central/northern plains
in the wake of the northern stream trough and as the California/Nevada trough
develops farther southward through Southern California and west of northern Baja California.
At the surface...a cold front attendant to the northern-stream trough
will advance southward through the Southern Plains...middle MS valley and middle
south...and into the northestern states. By 12z Monday...this boundary
should extend from eastern New York through the central Appalachians to northern
MS/la to central Texas.
..East Texas/southeastern OK/northern la/AR/nrn MS/southwestern Tennessee...
S/southwesterly low-level flow from the western Gulf of Mexico will support
moisture return in vicinity of an inverted trough extending from the middle
Texas coast through East Texas into Arkansas. Despite weak forcing aloft and
warm midlevel temperatures /per forecast soundings/ attendant to the
middle-upper-level ridging...sufficient low-level moistening and warm air advection
suggest mainly elevated thunderstorms will be possible. Isentropic ascent
and warm air advection will be the primary forcing mechanisms.
..central and Southern California coastal areas...
Steep lapse rates attendant to the cold midlevel trough across this
region should support thunderstorm development as this trough shifts southward.