Fire Weather Outlook Discussion
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FNUS28 KWNS 242118
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0317 PM CST Fri Nov 24 2017

Valid 261200Z - 021200Z

...Day 4/Mon - Portions of the Central and Southern High Plains...

An upper level ridge centered over the Plains will shift east on Day
4/Mon as a trough digs across the western U.S. and a secondary
shortwave trough tracks east across the Canadian prairie provinces.
As this occurs, a strong southwesterly mid/upper level jet streak
will overspread the Rockies into the northern Plains. At the
surface, low pressure will shift across the Canadian prairies with a
surface trough extending southwestward across the High Plains. A
secondary lee low may develop across southeast CO as well, further
enhancing gusty wind potential across the southern High Plains.
Breezy downslope winds will contribute to warming and drying across
parts of eastern WY into adjacent southwest SD, the NE Panhandle and
far northeast CO and elevated to locally critical fire weather
conditions will be possible.

Further south across parts of northeast NM, southeast CO and the
OK/TX Panhandles, elevated fire weather conditions also will be
possible. The strength of surface southwesterly winds will depend on
development of the lee low, but at least elevated conditions appear
likely given warm temperatures and low RH conditions overlapping
breezy southwest winds.

A cold front will drop south/southeast across the northern and
central Plains on Monday/Monday night and across the southern Plains
on Day 5/Tue. Some elevated fire weather potential may continue over
parts of the southern Plains behind the cold front on Tuesday, but
should remain short-lived, precluding probs at this time.

...Day 4-7/Mon-Thu - Southern California Coastal Ranges and
Foothills...

Quite a bit of uncertainty still exists in the forecast for Days
5-7/Tue-Thu. However, at least elevated fire weather potential
appears likely with offshore flow developing over the southern CA
coastal ranges and foothills beginning late night Day 4/Mon. An
upper level trough will move across CA on Day 4/Mon to the Four
Corners region by Day 5/Tue morning. This will lead to deep layer
northerly flow across southern CA. Light offshore winds and low RH
conditions will lead to elevated fire weather potential during this
time.

How the upper level pattern evolves after Day 5/Tue differs
considerably amongst medium range guidance, resulting in quite a bit
of uncertainty in the strength of offshore winds Days 6-7/Wed-Thu.
However, surface high pressure will build over the Pacific Northwest
and into the Great Basin during this time, leading to a favorable
offshore pressure gradient for light to moderate northeast surface
winds. Depending on the strength of the surface gradient and how an
upper level shortwave trough evolves over the western U.S, strong
offshore winds also could be possible and critical fire weather
conditions can not be ruled out. While 40% probs have been added to
address at least elevated fire weather concerns, confidence is too
low to introduce higher probabilities at this time and will wait to
see if better run-to-run and cross-model consistency occurs over the
coming day or two.

..Leitman.. 11/24/2017

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

$$


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