Fire Weather Outlook Discussion
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FNUS21 KWNS 231641

Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1040 AM CST Thu Feb 23 2017

Valid 231700Z - 241200Z


Adjustments have been made on the northern end of the
elevated/critical and extremely critical area, mainly over western
KS. Low level stratus has continued to slowly advance southward over
northwest KS with east to northeast winds across much of the state.
This will favor a cooler airmass being maintained, especially over
northwest KS. Given the latest observational data and model trends,
shifted the outlook areas southward. This will confine the extremely
critical and critical areas to southwest KS where clear skies and
stronger southwesterly low level winds are expected to result in
concerning fire weather potential this afternoon. Otherwise,
previous forecast philosophy remains unchanged.  Please see
discussion below for more details.

..Leitman.. 02/23/2017

.PREV DISCUSSION... /ISSUED 0115 AM CST Thu Feb 23 2017/

In the mid levels, a zone of broadly cyclonic and strong flow will
emerge over the central and southern High Plains, with the leading
edge of the stronger flow advancing toward the middle Mississippi
Valley through the period. As this occurs, a deep surface low is
forecast to track along a frontal zone from eastern CO to KS, before
it eventually advances to the middle Mississippi Valley. A dryline
extending south of the low will sharpen and move eastward over parts
of the Great Plains. A cold front trailing to the west/southwest of
the low will spread southeastward across parts of the Great Plains
during the evening and overnight hours. Deep vertical mixing into
the strong flow aloft west of the dryline and south of the front,
along with ample downslope-flow-enhanced warming/drying, will
greatly increase fire-weather potential across portions of the
Southwest States to the central and southern Great Plains.

...Portions of the Southwest States to the central and southern
Great Plains...
Across the Extremely Critical area, west-southwesterly to westerly
winds of 30-35 mph and gusts of 40-50 mph are forecast to combine
with RH of 8-10 percent during the afternoon. This will occur as
temperatures rise into the middle 60s to the 70s, except to around
80F in eastern parts of the TX Panhandle/South Plains into western
OK. These very strong downslope winds will support the very low RH,
especially given poor RH recovery during the preceding overnight
hours. Critical conditions could develop by late this morning,
before extremely critical conditions develop during the afternoon.
The presence of very dry fuels further supports the Extremely
Critical designation.

For many locations across the surrounding Critical area,
southwesterly to westerly winds of 20-30 mph are forecast to combine
with RH of 10-15 percent. One exception will be across portions of
central and eastern OK, where southerly to south-southwesterly winds
of 20-25 mph are forecast to combine with RH from the middle teens
to the upper 20s -- highest readings across eastern OK. These strong
surface winds are expected to occur in association with diurnally
enhanced vertical mixing into a low-level jet focused across eastern
OK around peak heating. Observational data suggest that moisture
return will be limited, and vertical mixing will encourage RH
reductions to the aforementioned values. While RH readings may not
reach Critical thresholds in some areas, they are expected to become
sufficiently low in the presence of abundant dry fine fuels and
strong winds for Critical designation.

Within the surrounding Elevated area, elevated to borderline-
critical fire-weather conditions are expected. However, critical
fire-weather conditions are not expected to occur on any more than a
brief/spotty basis.

Across portions of the central/southern Plains, a wind shift to
northwesterly is forecast to occur in association with the passage
of the cold front during the evening and overnight hours, which
could re-direct any ongoing fires. Also, a few thunderstorms may
affect parts of east-central CO and northern KS to the north of the
surface front during the late afternoon into the evening hours,
after elevated/critical fire-weather conditions occur. However,
these storms would more likely be accompanied by relatively higher
RH and cooler temperatures in the low levels.

...Please see for graphic product...

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