Valid 141200Z - 151200Z ...
Synopsis...
Widely scattered dry thunderstorms will continue to pose a fire weather risk across much of the West for today amid continued warm/dry conditions with widespread receptive fuels. Thunderstorm activity has been fairly widespread across the Great Basin and parts of the Pacific Northwest/northern Rockies over the past 24 hours. GOES IR/fire temperature imagery reveals multiple hot spots that have emerged during this period, possibly as a result of lightning strikes. MRMS rainfall estimates suggests that wetting rainfall was largely confined to the central Sierra Nevada and lower CO River Valley with little accumulation further north into the Great Basin.
A similar scenario is anticipated for today across a broad swath of the West. 00 UTC soundings continued to sample adequate mid-level moisture and sufficiently steep lapse rates to support weak convection, and GOES PWAT imagery suggests 0.5-0.9 inch PWAT values have spread east from the Great Basin into the central Rockies. While some low-level cooling/moistening from yesterday's convection is noted in surface temperature and RH trends, conditions in the lowest few kilometers should remain sufficiently dry to limit rainfall amounts. Thunderstorm coverage is expected to remain isolated to widely scattered with the exception of parts of the Sierra Nevada and lower CO River Valley where higher PWATS will favor a mix of wet/dry storms. Given the antecedent dry fuels and ongoing fires, dry lightning and strong outflow winds will continue to pose a fire weather concern.
...Columbia Basin...
A lee trough east of the Cascades is forecast to deepen this afternoon, which will result in strengthening downslope/gap winds into the Columbia Basin and through the Columbia Gorge. Ensemble guidance continues to show reasonably high probability for 15-20 mph winds with RH falling into the single digits to low teens. Elevated conditions are expected, and a few locations may see a couple hours of critical conditions with winds closer to 20 mph. Recent fire activity in the region indicates that fuels are receptive and should support the fire weather threat.
...Eastern Oregon into southern Idaho...
Recent model solutions have shifted the stronger mid-level flow northward away from the northern Great Basin. This trend appears to be supported by upper-air observations and analyses over the past 6-12 hours. Consequently, the potential for mixing down stronger flow to the surface appears to be reduced compared to previous forecasts. This trend is reflected in recent ensemble guidance with lower probability for sustained elevated conditions. The previous Elevated risk area has been removed given this trend, but areas of transient elevated wind/RH conditions will remain possible.
...Southern Montana to eastern Wyoming...
Patchy elevated fire weather conditions are likely this afternoon from south-central MT into eastern WY. A deepening surface low along the northern High Plains should support 15-20 mph downslope winds with RH values falling into the teens to low 20s. While the synoptic pattern favors a fire weather concern, deterministic solutions show considerable spread in the strengthen of winds and coverage/duration of elevated conditions - possibly due to the potential for convection by mid-afternoon. Likewise, only a modest signal is noted in ensemble guidance. However, given active wildfires in this region over the past 24 hours (mostly across southern MT), trends will be monitored for the need for highlights in future forecast updates.
..Moore.. 07/14/2024
Source: NWS
