Fire Weather Outlook Discussion
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FNUS22 KWNS 231907

Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0206 PM CDT Tue May 23 2017

Valid 241200Z - 251200Z

Biggest change to the ongoing outlook was to add an elevated area in
a large part of Montana for this update.  Here, strong downslope
flow (exceeding 35 mph in a few areas) and borderline-critical RH
values amidst areas of dry fuels support an elevated fire weather
threat.  One potential mitigating factor for a higher fire weather
threat will be areas of mid-level cloudiness and perhaps a few
thunderstorms, which may end up being wetting in nature given
0.5-0.8 inch precipitable water values especially in eastern
Montana.  However, models are trending toward drier low-level
conditions, and given dry fuels in some areas, an upgrade to
critical in some part of north-central Montana will be considered in
later updates.

Elsewhere, minor spatial adjustments to the elevated area in the
Southwest and Southern Rockies for this update.  Widespread elevated
(and perhaps locally critical) fire weather conditions will occur
across the region, with the highest fire weather threat existing in
eastern Arizona and west-central New Mexico.  Fuel states remain a
mitigating factor for a higher fire weather threat.

See the previous discussion below for more information.

..Cook.. 05/23/2017

.PREV DISCUSSION... /ISSUED 0200 AM CDT Tue May 23 2017/

Upper trough covering much of the central and eastern CONUS at the
beginning of the period is expected to shift eastward into more of
the eastern CONUS while the embedded upper low moves across the
middle MS Valley into the TN Valley. Upper ridging is expected
across the Plans in the wake of the upper trough with another
shortwave trough following behind the upper ridge across the
northern Rockies and Canadian prairie provinces. At the surface, a
large area of low pressure will drift across the eastern CONUS while
lee troughing deepens across the High Plains. Cyclogenesis is
anticipated within this lee troughing across eastern WY.

A more progressive upper pattern will foster a modest increase in
westerly flow aloft over the region. A tightening of the surface
pressure gradient is also expected as lower pressures from the High
Plains westward are paired with higher pressures across the Plains.
Deep boundary-layer mixed within this environment will result in
gusty winds across a large portion of the Southwest states. In
addition to increased wind speeds, a very dry antecedent airmass
will support afternoon RH values in the low teens and upper
single-digits. The combination of low RH and gusty winds will likely
result in meteorological conditions supportive of a critical fire
weather threat. However, fuel guidance continues to show ERC values
around the 60-75th percentile and above-average 100-hr and 1000-hr
fuel moisture, mitigating the overall fire weather threat. As a
result, elevated fire weather conditions are expected across a large
part of the Southwest. Some locally critical conditions are possible
in areas where fuels are sufficiently dry.

...Please see for graphic product...

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