Severe Storm Outlook Narrative (AC)
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ACUS03 KWNS 250726
SPC AC 250725

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0225 AM CDT Mon Mar 25 2019

Valid 271200Z - 281200Z


Thunderstorms are possible across portions of the Pacific Northwest
and northern California Wednesday. Isolated thunderstorms are also
possible across the southern High Plains and central Plains
Wednesday evening and overnight.

...Synopsis and Discussion...
Overall upper pattern is not expected to undergo any significant
changes on Wednesday. A compact shortwave trough extending from just
off the Carolina coast through the central FL Peninsula at the
beginning of the period will continue eastward farther offshore.
Farther west, strong southwesterly flow will persist from CA across
the Great Basin as upper low off the northern CA/Pacific Northwest
coast remains largely in place. Several low-amplitude shortwave
troughs will move within this southwesterly flow, providing the
impetus for thunderstorm development within the steep-lapse-rate
environment in place from central CA through western OR. Modest
instability is expected to limit overall updraft strength and
persistence. Even so, the strong vertical shear may compensate for
the weak instability and a few more-organized storms may develop.
These storms may be able to produce small hail. Limited coverage and
anticipated sub-severe hail size preclude delineated any outlook

Lee troughing will continue to deepen across the central and
southern High Plains, with eventual cyclogenesis across eastern CO.
Large-scale ascent will be weak but convergence along the lee trough
and near the surface low may provide enough lift for isolated
thunderstorms during the afternoon and evening. Primary forecast
uncertainty is the extent of air mass destabilization. Modest
moisture advection will be ongoing, but mixing will likely keep
dewpoints in the low 50s. Steep lapse rates over the region would
promote hail within any persistent updrafts. Isolated thunderstorms
are also possible later in the evening and overnight as warm-air
advection strengthens. Uncertainty remains too high to delineate any
areas with this outlook but areas may be needed in subsequent
outlooks, if confidence in sufficient storm coverage increases.

..Mosier.. 03/25/2019

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