FNUS22 KWNS 191849

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
1248 PM CST Tue Jan 19 2021

Valid 201200Z - 211200Z

The forecast remains on track for portions of southern California,
as RH recoveries across the area suggest that mainly Elevated
criteria surface conditions will persist past 12Z Wednesday.
Similarly, across the Plains states, RH varies considerably among
guidance members. Given the modest receptiveness of fuels and
surface westerly winds remaining below 25 mph on a widespread basis,
Elevated highlights have been withheld this outlook given the lack
of confidence for more widespread RH below 25% across the central
Plains. Lastly, 30-40% RH may be observed by afternoon peak heating
across portions of the Carolinas, Georgia, and the Florida
Peninsula, but weak winds preclude fire weather highlights despite
modestly receptive fuels in place.

..Squitieri.. 01/19/2021

.PREV DISCUSSION... /ISSUED 0146 AM CST Tue Jan 19 2021/

A stalled synoptic low off the coast of southern California/Baja
California is forecast to weaken through Wednesday evening, but will
continue to support strong offshore flow and a fire weather concern
for southern California for much of the day. Across the central
CONUS, a surface trough associated with a Canadian clipper low will
move southeastward through the day, ushering in breezy and dry
conditions for portions of the Plains.

...Coastal southern California...
Forecast guidance remains in good agreement that a -5 to -6 mb
LAX-DAG pressure gradient will remain in place for much of Wednesday
across southern CA as the synoptic low stalls offshore. Sustained
winds near 30-45 mph (gusting to 50-60 mph) appear likely for
portions of Los Angeles and Ventura counties with slightly weaker
winds in the peripheral coastal areas. Winds will be strongest
during the morning, and are expected to gradually weaken through the
evening/overnight hours. 

Despite the persistent strong winds, relative humidities will likely
improve through the day as moist air filters into the region. Cloud
cover and scattered rain showers will further limit RH reductions
for far southern CA where winds will likely remain elevated.
Ensemble and deterministic guidance show humidity values will most
likely improve into the 20-30% range for most coastal areas, but
reductions as low as 15% are possible where downslope warming/drying
can persist. Given the expected RH improvements, elevated fire
weather conditions appear most likely, but transient/localized
critical conditions are possible during the afternoon.

...central Plains...
Northwesterly winds are forecast to increase to around 15-20 mph
across the central Plains in the wake of a passing surface trough.
Although temperatures will remain on the cool side, dry air
advection and slight downsloping effects will allow RH values to
fall to near 20% across the broader WY/SD/NE region. This may allow
for areas of elevated fire weather conditions during the afternoon
hours when diurnal heating and boundary-layer mixing are maximized.
However, fuels across this region are only marginally receptive
(10-hour fuel moisture values in the low teens and ERC values in the
50-60th percentiles) after light precipitation over the past 24
hours. Because of this, no risk areas are introduced for this
outlook. Highlights may be needed in subsequent outlooks if guidance
trends windier or drier.

...Please see www.spc.noaa.gov/fire for graphic product...