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FNUS28 KWNS 152119
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0318 PM CST Fri Dec 15 2017

Valid 171200Z - 231200Z

An active, amplified mid/upper pattern will persist across the Lower
48 through the extended forecast period.  The primary synoptic
features for fire weather concerns through the period will be
occasional surges of high pressure into the Great Basin.  The
offshore gradient resulting from these high pressure areas will
result in occasional elevated to critical fire weather conditions -
particularly around D3/Sun and possibly again very late in the
forecast period (D7/Thu into D8/Fri Dec 22).  Elsewhere, elevated
fire weather conditions may develop in north-central California
around D3/Sun and again across portions of the high Plains of west
Texas/eastern New Mexico around D6/Wed through D7/Thu.

...Southern California...
Elevated to critical fire weather conditions will continue across
the region on D3/Sun in response to a continued dry airmass and
strong offshore pressure gradient.  Fuels remain dry across the
region due to a continued, extensive period of negligible rainfall.
Meanwhile, gusty northeasterly winds will continue - especially in
terrain-favored areas.

After D3/Sun, the offshore pressure gradient will slacken some and
result in overall weaker winds compared to previous days.  The
potential exists for onshore flow to commence around the
D6/Wednesday time frame, which should result in a brief period of
higher relative humidities.  After around D6/Wed, however, models
hint at another strong Santa Ana event commencing that will once
again elevate fire weather concerns.  Probabilities may be
reintroduced in later model cycles once greater certainty regarding
the onset of increased fire weather threat is achieved.

...D3/Sun - Northern/Central California...
An area of gusty northerly winds will develop across the region in
response to a strong surface pressure gradient and vertical mixing
of stronger mid-level flow.  A pre-existing dry airmass will remain
in place during that period, and RH values may fall to critical
thresholds during peak heating periods.  Low (40%) probabilities
have been introduced for this forecast period to address this fire
weather threat.

...D6/Wed onward - Southern High Plains...
Although models suggest that westerly downslope flow will increase
in response to lee troughing/surface cyclogenesis, models are not
particularly consistent regarding 1) specific placement of relevant
synoptic features and 2) degree of boundary layer drying within any
`dry` sector that can develop.  Nevertheless, any antecedent
precipitation shouldn`t be widespread enough to wet fuels in a wide
area - and fuels should be dry leading up to any potential fire
weather event.  Probabilities may need to be added as these
uncertainties are resolved in later outlooks.

..Cook.. 12/15/2017

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

$$


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