Valid 081200Z – 091200Z
…NO SEVERE THUNDERSTORM AREAS FORECAST…
A few lightning flashes may occur late in the period near the
Oregon/northern California coasts.
As an upper trough over the eastern U.S. at the start of the period
shifts across New England and into the Canadian Maritimes, upstream
ridging will amplify over the central U.S.
This ridge amplification will be aided by large-scale troughing
evolving over the West. The western troughing will be comprised
initially of a short-wave feature, that will cross the Great
Basin/Intermountain West through the first half of the period.
Meanwhile, a second trough — initially over the Gulf of Alaska —
will dig rapidly south-southeastward, toward the Pacific
Northwest/northern California coasts. Eventually, cyclonic flow
surrounding these two western features will merge into one large,
expanding area of cyclonic flow — which will grow to encompass the
entire western half of the CONUS by the end of period.
Little risk for convection is evident east of the Rockies through
the period, as high pressure prevails. In the West, a lack of
instability accompanying the initial short-wave trough crossing the
Intermountain West precludes any appreciable lightning risk. Late
in the period, a few strikes may occur near the California/Oregon
coastal region, as the second/digging trough nears. Elsewhere,
thunderstorms are not expected through the period.