Fire Weather Outlook Discussion
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FNUS22 KWNS 201855
FWDDY2

Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0154 PM CDT Thu Jul 20 2017

Valid 211200Z - 221200Z

...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN/CENTRAL
MONTANA...

Confidence in sufficiently strong winds has increased enough to
introduce a critical area for portions of Montana Friday. A modestly
enhanced surface pressure gradient will combine with downward mixing
of stronger flow aloft to support sustained westerly winds around
20-25 mph during the day. Additionally, diurnal mixing will
contribute to RH values around 10-20%. As fuels should remain quite
dry across much of the region, critical fire-weather concerns are
likely to materialize. Elsewhere, no changes are made to the ongoing
forecast.

..Picca.. 07/20/2017

.PREV DISCUSSION... /ISSUED 0210 AM CDT Thu Jul 20 2017/

...Synopsis...
An upper trough/low over AB/SK Friday morning will continue moving
eastward across the Canadian Prairie provinces through the period.
Around 35-45 kt of mid-level westerlies attendant to this trough
will overspread much of MT and vicinity by Friday afternoon. At the
surface, an area of low pressure across the northern High Plains
should develop slowly eastward into the Dakotas through Friday
evening. A trailing cold front should move southeastward across the
northern/central High Plains.

...Portions of the Northern Great Basin into the Northern
Rockies/High Plains...
Strong/gusty westerly winds of 15-20 mph are expected to develop
behind the previously mentioned surface cold front Friday afternoon
along and east of the Rockies. Diurnal heating and a downslope
component to these winds will likely warm and dry the boundary
layer, and RH values of 7-20% should develop across much of
central/eastern MT by peak heating. An elevated fire weather area
has been made for parts of the northern High Plains to account for
this threat, and some potential exists for an upgrade to critical
delineation where sustained winds may exceed 20 mph. However,
forecast winds in short-term guidance remain too marginal to
delineate a critical area at this time.

A small corridor of elevated conditions is also forecast to occur
across part of the Snake River Valley in southern ID Friday
afternoon/evening. Here, sustained winds of 15-20 mph should combine
with RH values generally between 7-15%. The lack of stronger
forecast winds precludes a critical designation.

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

$$


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