Valid 072000Z – 081200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
OVER PORTIONS OF THE SACRAMENTO VALLEY OF CALIFORNIA….
…SUMMARY…
A marginal tornado threat exists this afternoon across portions of
northern California.
The forecast remains on track with no changes needed. A small
pocket of heating in the Sacramento area may aid in the development
of isolated thunderstorms this afternoon over parts of the
Sacramento Valley. However, the risk of rotating storms and/or
brief tornadoes is expected to remain marginal.
..Hart/Nauslar.. 12/07/2019
.PREV DISCUSSION… /ISSUED 1021 AM CST Sat Dec 07 2019/
…Northern California…
No significant changes have been made to the ongoing forecast.
Morning water vapor loop shows a strong upper low around 40N/129W,
with a lead shortwave trough and associated midlevel speed max
rotating toward the coast. Numerous bands and clusters of
precipitation will continue to move onshore over this region today,
but there will also be short-lived periods of
heating/destabilization. Despite near moist-adiabatic lapse rates
aloft, surface dewpoints in the low/mid 50s and temperatures locally
approaching 60 will result in just enough CAPE to pose a risk of a
few rotating storms. Orographically backed low-level winds could
result in a brief tornado or two today in parts of the northern
valley. Overall, the risk seems low and the ongoing MRGL risk
forecast seems to capture it sufficiently.
$$