SPC 1200Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1224 AM CDT Sat Oct 17 2020

Valid 171200Z - 181200Z


Severe thunderstorms are not expected across the contiguous United
States on Saturday.

...Lower MS Valley...

Broad mid-level troughing will persist across the middle of the
country this weekend. Latest model guidance suggests several notable
short-wave troughs will dig southeast across the northern Rockies
toward the lower MS Valley. These features will collectively induce
more favorable low-level trajectories for moisture to advance across
the western Gulf basin through east TX into AR by the end of the
period. LLJ is forecast to increase from central TX into northern AR
during the latter half of the period and this should be the primary
mechanism for ascent atop the boundary layer after sunset. Forecast
soundings suggest profiles will become increasingly buoyant if
lifting parcels near 850mb, and scattered convection should evolve
across this region late. Modest mid-level lapse rates and strong
cloud-layer shear suggest some of this activity could briefly
organize; however, instability will likely be too limited to warrant
any meaningful threat for severe probabilities.


As a strong surface anticyclone settles into southern New England,
easterly low-level flow should deepen across the southern periphery
of this feature over south FL. As a result, high-PW air mass will
linger across this region with PW values expected to hold near 2
inches. Very moist profiles and poor lapse rates suggest mostly weak
convection with opportunities for lightning at times.

..Darrow/Lyons.. 10/17/2020

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