SPC 0830Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0135 AM CST Sat Feb 20 2021

Valid 221200Z - 231200Z


The risk for severe thunderstorms appears negligible across the
U.S., Monday through Monday night.

Models indicate that mid-level ridging will be maintained along an
east-west axis across the mid-latitude eastern Pacific through this
period.  Within the westerlies to the north-northwest of this
feature, short wave ridging is forecast to build across the
northeastern Pacific into southwestern Alaska.  As this occurs,
progressive downstream flow appears likely to take on an increasing
northwesterly component near the British Columbia coast into the
Pacific Northwest, while remaining west-northwesterly to westerly
across the interior U.S. through the Atlantic Seaboard.

Within this regime, significant mid-level troughing shifting east of
the Mississippi Valley by 12Z Monday is forecast to continue
eastward.  As it overspreads the Atlantic Seaboard late Monday
afternoon through Monday night, it may be accompanied by secondary
cyclogenesis off the middle and northern Atlantic coast, and a
strengthening cold front across the south Atlantic coast into the
adjacent western Atlantic.

Ahead of the front, an influx of moisture, off a moistening boundary
layer over the northeastern Gulf of Mexico, may contribute to weak
CAPE across the Florida Panhandle into parts of southern Georgia and
the Carolinas during the day Monday.  However, it appears that this
instability will generally rooted above the boundary layer, and the
extent to which this may contribute to convection capable of
producing lightning remains unclear.  Somewhat better potential for
boundary-layer based, or near boundary-layer based, thunderstorm
development appears to exist ahead of the front across northern
portions of the Florida Peninsula and coastal North Carolina by
Monday evening.  Substantially higher thunderstorm probabilities,
though, appear focused offshore Monday night, near the Gulf Stream,
in association with more favorable phasing of low-level
destabilization and forcing for ascent.

..Kerr.. 02/20/2021

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