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U.S. Day 1 Fire Weather Outlook
ZCZC SPCFWDDY1 ALL
FNUS21 KWNS 160702
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0202 AM CDT Sat Aug 16 2025
Valid 161200Z - 171200Z
...Synopsis...
A broad mid-level trough over the Northwestern US is forecast to
consolidate and intensify today/tonight as it impinges on the
northwestern edge of a ridge of high pressure over the central US.
The tightening height gradient will bolster flow aloft, while at the
same time, a surface cold front will move in from the Northwest.
Monsoon moisture will support showers and thunderstorms along/ahead
of the front, while localized dry and breezy conditions are possible
over the Southwestern US.
...Northwest and Rockies Dry Thunder...
Across the Northwest and central Rockies, persistent monsoon
moisture will be in palace ahead of the upper trough and attendant
cold front. Increasing PWATs (0.8-1 inch) will favor a mix of wet
and dry storms across far northern CA into eastern OR and ID/MT from
the afternoon into the evening hours. While the air mass in the
low-levels will not be as dry as recent days, with increasing RH
ahead of the front, 30-40 kt of mid-level flow should support faster
northeastward storm motions of 25-30 kt. This will allow for less
wetting rainfall as storms track eastward over areas of very
receptive fuels supportive of lightning ignitions. Additionally,
gusty outflow winds are expected, potentially impacting existing
active fires across the area. The risk for lightning may continue
overnight as the upper trough and front shift eastward towards ID
and MT. IsoDryT highlights will remain, and have been expanded over
areas of the expected driest fuels and storms.
...Southern Great Basin...
As the mid-level trough continues eastward across the Northwest,
southwesterly flow aloft should continue to promote locally breezy
and dry conditions across portions of southern NV and western UT.
South-southwest winds of up to 15 mph, along with daytime relative
humidity as low as 15%, are expected in some valleys in the southern
Great Basin. Amidst dry fuels, some locally elevated fire-weather
conditions are possible. The lack of stronger winds for now
precludes elevated highlights.
..Lyons.. 08/16/2025
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U.S. Day 2 Fire Weather Outlook
ZCZC SPCFWDDY2 ALL
FNUS22 KWNS 160704
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0204 AM CDT Sat Aug 16 2025
Valid 171200Z - 181200Z
...Synopsis...
Across the US, broad ridging is forecast to expand while troughing
consolidates over the West. As height aloft build, very warm surface
temperatures are expected over parts of the southern and
Southwestern CONUS. A belt of stronger flow aloft will impinge on
the northern Rockies as the trough and a weak surface cold front
approach. Monsoon moisture should support dry thunderstorms, while
light winds and dry conditions will persist elsewhere Sunday.
...Northern Rockies Dry Thunder...
Troughing should continue to intensify as it moves into the Great
Basin and Rockies Sunday, as a cold front moves in from the west.
This will allow for additional monsoon moisture to filter northward,
supporting scattered showers and thunderstorms through the
afternoon. Despite PWATs climbing to near 0.8 to 1 inches, a mix of
wet and dry thunderstorms is expected ahead of the front from
northern CA into the Northern Rockies. While not as dry as previous
days, stronger flow aloft is expected ahead of the deepening trough.
This should allow for a favorable alignment of drier/more receptive
fuels and faster northeast thunderstorm motions to limit rainfall
across northern NV into central ID and western MT. Thus, isolated
dry lightning and ignitions are likely to remain a concern across
the receptive fuels beds of the northern Great Basin and Rockies
Sunday.
...Southern NV into southwest UT
South of the western US troughing and stronger flow aloft, another
day of dry and locally breezy conditions is expected over parts of
the southern Great Basin. While displaced from the stronger flow,
localized 15 mph surface winds and low RH below 15% are likely
across southern NV and southwest UT. With area fuels very dry and
receptive, some locally elevated fire-weather conditions are
possible, though widespread occurrence is unlikely owing to the
modest winds.
..Lyons.. 08/16/2025
U.S. Day 3-8 Fire Weather Outlook
ZCZC SPCFWDD38 ALL
FNUS28 KWNS 152158
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0458 PM CDT Fri Aug 15 2025
Valid 171200Z - 231200Z
...Day 3/Sunday...
A mid-level trough across the Pacific Northwest along with a diffuse
frontal boundary along a corridor of Pacific moisture will promote a
mix of wet and dry thunderstorms from northern CA into the Northern
Rockies. Alignment of drier, more receptive fuels and faster
northeast thunderstorm motions limiting rainfall are expected across
northern NV into central ID. A 10 percent dry thunderstorm
probability was maintained to cover this threat. A dry southwest
flow pattern between the Pacific Northwest trough and upper-level
ridge across the Southern U.S. will promote sustained
south-southwest winds of up to 15 mph along with low daytime
relative humidity of around 15 percent across southern NV amid very
dry fuels. However, widespread critical fire weather conditions are
not expected.
...Day 4/Monday - Day 8/Friday...
Mid-level troughing will moderate fire weather concerns across the
Northwestern U.S. early next week while the Southern U.S.
mid/upper-level ridge begins to shift and strengthen into the Four
Corners region. Ridging amplifies well into the Northern Rockies by
Day 5/Tuesday with gradual expansion and westward propagation into
the West Coast by Day 8/Friday. Above normal surface temperatures
will similarly expand across most of the western U.S. by the end of
next week. A return of monsoon moisture into the Intermountain West
could pose a dry thunderstorm threat across the eastern Great Basin
beginning on Day 6/Wednesday translating northward to include UT by
Day 7/Thursday and WY by Day 8/Friday. Uncertainty in magnitude of
moisture return and subsequent thunderstorm coverage precludes
introducing dry thunderstorm probabilities at this time.
..Williams.. 08/15/2025
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