SPC 1630Z Day 1 Outlook

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1008 AM CST Tue Feb 23 2021

Valid 231630Z – 241200Z

…NO SEVERE THUNDERSTORM AREAS FORECAST…

…SUMMARY…
Isolated thunderstorms will be possible across the Pacific Northwest
and northern Rockies this afternoon and evening, as well as along
the southeast Florida coast.

…Synopsis…
An initial shortwave trough will move east-southeastward over the
Dakotas today to the upper MS Valley tonight, as an upstream trough
digs south-southeastward from BC to he northern Rockies through
tonight. Morning soundings from WA/MT and southern BC/AB show steep
midlevel lapse rates of 8-9 C/km in association with cold midlevel
temperatures (-32 to -38 C at 500 mb) on the cyclonic side of the
mid-upper jet. Even modest daytime heating/mixing will contribute
to weak surface-based CAPE from the WA Cascades eastward to western
MT, where convective snow/rain showers are expected. Though CAPE
will be limited to 100-200 J/kg, the cold profiles will allow
sufficient cloud depth for isolated lightning flashes with the
deeper convective cells, primarily this afternoon/evening.

Otherwise, a slow-moving front will linger near the southeast FL
coast through tonight. A slightly pre-frontal band of convective
showers will move just southeast of the mainland coast/Keys by
midday, but there will still be potential for isolated thunderstorm
development along the front near the coast this afternoon.

..Thompson.. 02/23/2021

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Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1008 AM CST Tue Feb 23 2021

Valid 231630Z - 241200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Isolated thunderstorms will be possible across the Pacific Northwest
and northern Rockies this afternoon and evening, as well as along
the southeast Florida coast.

...Synopsis...
An initial shortwave trough will move east-southeastward over the
Dakotas today to the upper MS Valley tonight, as an upstream trough
digs south-southeastward from BC to he northern Rockies through
tonight.  Morning soundings from WA/MT and southern BC/AB show steep
midlevel lapse rates of 8-9 C/km in association with cold midlevel
temperatures (-32 to -38 C at 500 mb) on the cyclonic side of the
mid-upper jet.  Even modest daytime heating/mixing will contribute
to weak surface-based CAPE from the WA Cascades eastward to western
MT, where convective snow/rain showers are expected.  Though CAPE
will be limited to 100-200 J/kg, the cold profiles will allow
sufficient cloud depth for isolated lightning flashes with the
deeper convective cells, primarily this afternoon/evening.

Otherwise, a slow-moving front will linger near the southeast FL
coast through tonight.  A slightly pre-frontal band of convective
showers will move just southeast of the mainland coast/Keys by
midday, but there will still be potential for isolated thunderstorm
development along the front near the coast this afternoon.

..Thompson.. 02/23/2021

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