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FNUS21 KWNS 161609

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1008 AM CST Sat Dec 16 2017

Valid 161700Z - 171200Z


The ongoing forecast is on track with no changes needed.  Several
areas of gusty northerly/northeasterly flow will persist across
portions of California today amidst very low RH values, resulting in
potential for rapid fire spread.  Farther east in the Plains,
elevated fire weather conditions will develop for a few hours in the
afternoon with RH values falling to around 15-20% within the
elevated area.  Locally elevated fire weather conditions can also be
expected in northeastern Oklahoma and vicinity, where 10-20 mph
southerly winds will briefly combine with minimum RH values of
around 25-30%.

See the previous forecast below for more detail.

..Cook.. 12/16/2017

.PREV DISCUSSION... /ISSUED 0156 AM CST Sat Dec 16 2017/

Strong northerly deep-layer flow on the back side of an amplifying
upper trough over the Great Basin will overspread much of CA today.
At the same time, surface high pressure will build over the Pacific
Northwest today, and into the Great Basin tonight. This will result
in an increasing surface pressure gradient first over northern CA.
As stronger high pressure slides southward into the Great Basin this
evening, offshore gradients will increase over southern CA. The net
result will be a large area of elevated to critical fire weather
conditions across much of California today and tonight.

Increasing southerly deep-layer flow will overspread the southern
Plains today as a shortwave trough lifts northeast from northern
Mexico into TX by this evening. At the surface, a lee low will
develop over the central/southern High Plains and an increasing
pressure gradient across the region will aid in development of gusty
surface winds and elevated fire weather conditions will be possible.

...Portions of Central into Northern CA Today and Tonight...

Gusty north winds were already occurring as of 07z across portions
of the Bay Area mountains and foothills. RH values are expected to
fall critically low later this morning and elevated to critical
conditions are expected to persist through the remainder of the
period across portions of central into northern CA. Critical
conditions are most likely in the mountains and foothills near the
Bay Area southward along the Diablo and Santa Cruz Mountain Ranges
into adjacent portions of the Sacramento Valley. RH values will fall
into the 10-20 percent range during the day with north winds around
15-30 mph with higher gusts possible.

...Portions of Southern CA...

Gusty winds were already occurring as of 07z across parts of the
Santa Barbara County mountains in conjunction with very low RH.
Critical conditions will continue through this evening as north to
northeast winds of 15-25 mph with stronger gusts persist. Further
south and east toward Ventura, Los Angeles, Orange and western San
Bernardino and Riverside Counties, gusty northeasterly winds will
return Saturday night into Sunday morning. Expect sustained winds of
20-30 mph with higher gusts. RH values will fall into the 15-25
percent range Saturday night, before falling further during the day
on Sunday.

...Portions of the Central and Southern High Plains...

Breezy and dry conditions are expected across portions of the
central and southern High Plains today. As temperatures warm into
the 50s to low 60s, boundary-layer mixing to around 2-3kft will
ensue, resulting in further drying and downward transport of
stronger midlevel winds. RH values of 20-30 percent will be
widespread with sustained winds around 15-20 mph and higher gusts.

...Please see for graphic product...

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