Valid 121630Z – 131200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ALONG PORTIONS
OF THE WASHINGTON AND OREGON COAST….
A marginal risk for brief tornadoes will persist through the early
afternoon along parts of the Washington and Oregon coast.
IR satellite imagery shows a compact and fast-moving shortwave
trough about 150nm west of Portland, Oregon. This feature and an
associated cold front will approach the coast of WA/OR in the next
few hours. A pocket of persistent lightning activity is noted ahead
of this feature, and radar suggests that scattered showers and
thunderstorms will begin moving ashore soon. Instability parameters
are quite weak with CAPE values below 200 J/kg. Nevertheless,
orographically enhanced low-level shear profiles may be sufficient
for a brief spinup as convection moves onshore. This threat is
expected to decrease by late afternoon as the cold front passes and
low-level winds veer.