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Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0246 PM CDT Tue Sep 06 2022

Valid 071200Z - 081200Z

...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF
NORTH-CENTRAL MONTANA...
...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL MONTANA...

An Extremely Critical area was added for north-central Montana.
Strong mid-level winds will coincide with deep boundary-layer mixing
and a strong surface pressure gradient to promote 25-35 mph
sustained winds with gusts potentially 50-60 mph. Areas of
single-digit RH are possible, but it is not certain how widespread
these extremely dry conditions will be on account of increasing
high-level clouds.

A Scattered Dry Thunderstorm area was also considered for parts of
central Idaho into adjacent southwestern Montana. Some
convection-allowing guidance does show this potential. However,
thermodynamic profiles show some potential for lightning efficiency
of the convection to be on the lower end. Confidence is too low for
an upgrade at this time, but forecast trends will need to be
monitored.

Elsewhere, the forecast remains primarily on track with only minimal
changes.

..Wendt.. 09/06/2022

.PREV DISCUSSION... /ISSUED 0206 AM CDT Tue Sep 06 2022/

...Synopsis...
Fire weather concerns will increase on Wednesday as an upper trough,
currently approaching the northeast Pacific, shifts into the Pacific
Northwest/Western Canada and aids in deepening a lee cyclone over
the western Canadian Prairies. In addition to strengthening regional
pressure gradient winds, this feature will support increasing
thunderstorm potential over the Northwest. Limited moisture will
favor mainly dry thunderstorms. 

...Pacific Northwest and Northern Rockies...
Latest surface observations across the Pacific Northwest and
northern Rockies show dewpoint values in the 10th to 25th
percentiles co*pared to seasonal normal values. This dry air is
expected to linger across the region into Wednesday despite some
moistening aloft. As west/southwest mid-level flow increases,
downslope winds will foster additional drying/warming in the lee of
prominent terrain features. Most guidance suggests RH reductions
into the 10-20% range are likely from the Cascades eastward into
northern High Plains. Sustained winds between 15-20 mph will be
co*mon with frequent gusts into the 25-35 mph range. Recent fire
activity across the region indicates that fuels are receptive, and
will remain so through Wednesday afternoon given persistent hot/dry
conditions. 

The driest/windiest conditions are expected to develop across
northern MT under a belt of 40-50 knot mid-level winds. Deep
boundary-layer mixing through 600 mb will facilitate efficient
downward transfer of these winds. Sustained winds near 25 mph are
likely with frequent gusts between 35-45 mph (and possibly as high
as 50 mph in the lee of the northern Rockies). The strong downslope
flow regime will drive RH values into the low teens, and may support
periods of extremely critical fire weather conditions for
north-central MT.  

...Dry Thunderstorms...
Recent precipitable water imagery shows modest 700-500 mb moisture
return along the West Coast towards the Pacific Northwest. A
secondary plume of mid-level moisture is noted ahead of the
approaching wave. Both features will act to increase column moisture
across the Pacific Northwest over the next 48 hours to around
0.5-0.75 inch. While modest, forecast soundings signal that this
will be sufficient to support around 100-250 J/kg MUCAPE atop a
deep, well-mixed boundary layer. Forcing for ascent along/ahead of a
cold front will support isolated thunderstorms by late afternoon
with an associated threat of dry lightning and strong outflows. This
overall synoptic regime is favorable for a dry thunderstorms across
a large area, though a fairly weak convective signal in most
deterministic guidance and latest hi-res ensemble guidance suggests
that storm coverage will likely remain limited. Nonetheless, recent
fire activity indicates that fuels remain receptive across the
region and will support a lightning-driven fire weather concern.

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