U.S. Severe Weather Forecast (Convective Outlook)

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Day Three

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acus03 kwns 270831 
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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 
southwest Tennessee. 


... 
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. 


.Peters.. 02/27/2015