SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0140 PM CST Mon Nov 16 2020

Valid 162000Z - 171200Z


Severe thunderstorms are not expected across the contiguous U.S.
through tonight.

...20Z Outlook Update...

...Pacific Northwest...
Convection associated with weak CAPE is evident within a warm
frontal precipitation band overspreading the region.  The southern
edge of the heavier precipitation (west of the Cascades) is
currently near the Columbia River and forecast to shift north of the
Puget Sound vicinity by around 03-05Z, with substantive lower/mid
tropospheric drying into its wake.  

Despite the presence of the convection, initially warm and saturated
thermodynamic profiles appear to be inhibiting the development of
lightning.  Even near the leading edge of the mid-level drying, warm
layers aloft still appear inhibitive, and an area of offshore
lightning (roughly near 45N/126W) between 16-17Z appears to have
been short lived.

...South Florida...
Relatively warm and dry mid-levels, coupled with generally weak
low-level convergence, continues to inhibit thunderstorm
development.  However, models indicate at least some increase in
low-level convergence along coastal areas near/north of Palm Beach
later this afternoon through tonight, which might still support the
risk for an isolated weak thunderstorm or two, in the presence of
weak instability.

..Kerr.. 11/16/2020

.PREV DISCUSSION... /ISSUED 1015 AM CST Mon Nov 16 2020/

...South FL...
Isolated showers currently east-southeast of the Space Coast should
increase in coverage as they spread southwestward along/ahead of a
weakly convergent cold front pushing south from central FL. Rather
poor 700-500 mb lapse rates between 4-5 C/km as sampled by regional
12Z soundings will be a limiting factor to sustaining charge
separation, but adequate buoyancy exists for a risk of isolated

...Coastal WA...
A pronounced low-level warm advection regime will shift north from
the Columbia Valley today. Scant elevated buoyancy may develop as
850-mb dew points rise to around 9 C this afternoon. Very isolated
lightning could accompany deeper showers through early evening.

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