Day 1 Fire WX discussion from the SPC 7/27/2018


#1

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0119 AM CDT Fri Jul 27 2018

Valid 271200Z - 281200Z

…Synopsis…
Very warm, dry surface conditions will persist across portions of
the West beneath a strong mid-level ridge. A belt of 20-35 kt
mid-level flow will extend from Oregon eastward to Idaho/Montana
throughout the day. Some of this flow will mix to the surface,
resulting in broad areas of locally elevated conditions from
California to Idaho and southwestern Wyoming. Additionally, a few
isolated dry lightning strikes may occur from the Pacific Northwest
into portions of the northern Rockies.

…Southern Idaho into southwestern Wyoming…
Warm, dry conditions will develop across this region as temperatures
rise into the 80s and 90s F during peak heating. Broad areas of
10-15 mph westerly surface flow will develop due to vertical mixing
and pressure gradient processes. Subtle terrain forcing (i.e., the
Snake River Basin) will foster slightly stronger winds exceeding 20
mph at times amidst the dry surface conditions. These areas (with
stronger surface winds and dry fuels) have been highlighted with
elevated fire weather delineations for this outlook.

…Inland California northward into Oregon…
Hot, dry conditions are expected to continue even at the beginning
of the period due to the previous night’s poor recovery. Surface
temperatures will warm into the 100s-110s F through peak heating
hours - warmest across central California and vicinity. Generally
weak surface flow and critically low RH values (5-15%) should foster
mostly plume-dominated fires, although localized terrain influences
have resulted in locally elevated fire weather conditions and rapid
fire spread given very dry fuels across the region. A broader area
of 15 mph northwesterly surface flow will develop during the
afternoon in portions of the San Joaquin Valley, and an elevated
fire weather area has been delineated there.

…Pacific Northwest into western Montana…
Weak mid-level instability will develop across the region during
peak heating, and a few thunderstorms are expected to develop as a
result. Moisture/kinematic profiles do not support widespread dry
thunderstorm activity, although a few localized areas may experience
isolated dry lightning strikes amidst dry fuels.