Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 211935
SPC AC 211934

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0234 PM CDT Wed Mar 21 2018

Valid 212000Z - 221200Z


A few thunderstorms are possible this afternoon and evening across
parts of central and northern California and the Great Basin.

...20Z Update...

...Northern/Central California...
Temperatures have warmed into the upper 50s/low 60s across southern
portions of the Sacramento Valley with dewpoints also increasing a
few degrees into the mid to upper 50s. Abundant cloud cover has
tempered heating thus far with that general trend expected to
persist. Even so, subtle increases in surface temperatures and
dewpoints will result in a modestly unstable environment and the
potential for isolated thunderstorms. Surface winds are currently
southerly/southeasterly across the region and recent VAD wind
profiles from KDAX show favorable low-level shear (0-1 km bulk shear
from 15-20 kt and 0-3 km SRH over 150 m2 per s2). If a storm was
able to persist, some potential for low-level storm rotation exists.
However, given the uncertainties regarding destabilization and
expectation for generally isolated thunderstorms, severe storm
probabilities remain too low for an outlook area.

..Mosier.. 03/21/2018

.PREV DISCUSSION... /ISSUED 1130 AM CDT Wed Mar 21 2018/

A moderately strong sub-tropical/low-latitude belt of moist
southwesterly flow extends into the region to the south of a
southward-digging upper trough off the coast of British Columbia and
the Pacific Northwest. Periodic/isolated thunderstorms can be
expected particularly across parts of the Sacramento Valley as well
as coastal areas of northern/central California today into this

Although scattered precipitation and lingering cloudiness is likely
to temper overall destabilization, short-term RAP/NAM forecast
soundings across the Sacramento Valley suggest some potential for
modest surface-based destabilization later this afternoon coincident
with more than adequate low-level/deep-layer shear for organized
low-topped storm modes. Although a lack of more appreciable
heating/destabilization is currently expected to preclude a
meaningful hail and/or brief tornado risk, will continue to monitor
short-term trends and reevaluate any need for low severe
probabilities in the subsequent 20Z Outlook.

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