Fire Weather Outlook Discussion
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000
FNUS28 KWNS 252159
FWDD38

Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0458 PM CDT Tue Apr 25 2017

Valid 271200Z - 031200Z

Enhanced mid-level winds over the western CONUS should foster
increased fire weather concerns across portions of the Southwest and
southern Plains through much of the extended forecast period.
Elevated to critical conditions will be possible most afternoons
from Day 3/Thursday through at least Day 6/Sunday across parts of
these regions.

...Day 3/Thursday - Day 8/Tuesday: Portions of the Southwest and
Southern Plains...
A mid-level jet axis will remain centered over the Southwest and
southern High Plains on Day 3/Thursday. Latest guidance remains in
good agreement with the overlap of strong low-level winds across NM
into west TX with critically lowered RH values. Therefore, the
70%/critical area has been maintained with no changes across parts
of central/southern NM into far west TX, where fuels are expected to
remain favorable for large fire starts.

Medium-range guidance is consistent in showing amplification of an
upper trough/low over the Great Basin/Four Corners area on Day
4/Friday. A 40%/marginal area has been maintained with minor changes
across parts of the southern High Plains to account for the
possibility of a sufficient overlap of strong/gusty winds and
lowered RH values. A separate 40%/marginal area has been expanded
from the lower CO River Valley eastward into parts of western AZ per
latest guidance, as strong northwesterly mid-level winds should
translate to the surface and combine with RH values approaching
critical levels.

For Day 5/Saturday, the strongest mid-level winds associated with an
eastward-moving upper trough/low should remain confined to a narrow
corridor across the Southwest and southern High Plains. Confidence
has increased sufficiently in strong low-level winds occurring
across this corridor to introduce a 40%/marginal area for Day
5/Saturday extending from the lower CO River Valley to the southern
High Plains. Guidance differs on the degree of RH reduction across
these regions, however, precluding a 70%/critical delineation.

For Day 6/Sunday, the upper trough/low centered over the Plains
should develop northeastward towards the upper MS Valley and Upper
Midwest, with a belt of enhanced northwesterly mid-level winds
mainly confined to parts of TX along the Rio Grande. Enough
agreement exists amongst medium-range model guidance in the
placement of strong/gusty winds and lowered RH values to introduce a
40%/marginal area from west TX along the Rio Grande Valley to deep
south TX on Day 6/Sunday.

By Day 7/Monday and continuing into Day 8/Tuesday, it appears that
the potential for widespread critical fire weather conditions may
lessen somewhat across the Southwest and southern High Plains, as
enhanced mid-level flow remains mostly displaced to the north and
east of these regions. Therefore, no probabilities have been
included at this extended time frame.

...Day 4/Friday - Day 5/Saturday: Portions of Southern CA...
Strong northwesterly winds associated with a mid-level jet should
overspread portions of central/southern CA Friday afternoon. A
strengthening surface pressure gradient across the Great Basin and
CA may also lend some support to gusty offshore northerly to
northeasterly winds across portions of southern CA from Day 4/Friday
into Day 5/Saturday. Confidence in RH values becoming lowered and
fuels being receptive remains high enough to continue a 40%/marginal
area across portions of southern CA for both days. Mid-level flow
and the surface pressure gradient are forecast to weaken by Day
6/Sunday, which should lessen the fire weather threat.

...Day 3/Thursday - Day 6/Sunday: Portions of the FL Peninsula...
A relatively dry low-level airmass is forecast to remain across much
of the FL peninsula through at least Day 6/Sunday in the wake of a
prior frontal intrusion. RH values may fall near to/below critical
thresholds each afternoon across interior portions of the FL
peninsula. However, forecast wind speeds do not appear sufficiently
strong to support widespread critical fire weather conditions any
day, which precludes the introduction of 40%/marginal probabilities.

..Gleason.. 04/25/2017

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

$$


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