.PREV DISCUSSION... /ISSUED 0121 AM CDT Mon Oct 09 2017/
...Synopsis...
An upper trough over the Four Corners region will pivot eastward
across the southern Rockies today and the central and southern
Plains tonight. Across much of the Pacific coast, deep-layer
northerly flow will gradually become westerly as an upper ridge
deamplifies ahead of the next upper trough off the Pacific Northwest
coast by the end of the period. At the surface, strong high pressure
over the Great Basin will result in a tight gradient across CA and
strong offshore winds are expected across southern CA. Additional
strong offshore winds will continue across portions of the Bay Area
and into the central valley/west slopes of the Sierras through at
least midday.
...Portions of Northern California...
Strong north-northeasterly winds are ongoing early this morning in
the higher elevations near the Bay Area and the adjacent Sacramento
Valley and western slopes of the Sierra. Observations as of 06z
showed winds around 10-20 mph with gusts to 40 mph and RH values in
the 12-25 percent range. As a result, elevated to locally critical
fire weather conditions are expected. These conditions will continue
into early afternoon before wind speed begin to weaken. However, RH
values will remain low until later tonight.
...Portions of Southern California...
Strong offshore/Santa Ana winds are expected for much of the Day 1
period as a favorable pressure gradient remains in place into
Tuesday morning, and widespread critical fire weather conditions are
expected.
Wind speeds will increase this morning with 25-40 mph sustained,
gusting to 70 mph expected in the Ventura and L.A. County mountains
and valleys. Toward the L.A. basin/San Gabriel Valley wind speeds
will be a touch lower at 20-35 mph with gusts to 60 mph possible. In
addition to strong, potentially damaging winds, RH values will be
very low from the single digits to 15 percent. Area fuels are
critically dry and fires will spread quickly should ignitions occur.
Further south, toward Orange County and the Inland Empire and the
San Diego County mountains, wind speeds will still be strong, but
not as strong as further north. Expect sustained speeds of 20-30 mph
with gusts to 45 mph to be common in these areas. RH values will
fall into the single digits to 15 percent. These conditions will
persist into the nighttime hours and early Tuesday morning.
...Please see www.spc.noaa.gov/fire for graphic product...