Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0206 AM CDT Tue Aug 11 2020 Valid 111200Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN WASHINGTON AND NORTHERN OREGON... ...Synopsis... A mid-level trough will amplify across the Pacific Northwest throughout the period, with strengthening flow aloft overspreading a warming/mixing boundary layer through the afternoon hours. The stronger flow aloft is expected to mix down to the surface to encourage dry and windy conditions supportive of wildfire spread across portions of the Pacific Northwest and northern Rockies. Large-scale lift associated with the mid-level trough is also expected to support thunderstorm development within a west-east band of mid-level moisture across the northern Great Basin into the central Rockies, where dry lightning may also encourage new wildfire ignitions. Finally, modest flow aloft associated with a small impulse overspreading the southwest CONUS may also support surface dry and windy conditions, where some wildfire spread potential may be noted by afternoon peak heating. ...Pacific Northwest and parts of the Northern Rockies... By afternoon, downslope along the lee of the Cascades will promote at least 15 mph sustained westerly winds and 15-25% RH across much of the Columbia and Harney Basins. High-resolution model guidance continues to indicate Critical conditions (with 20 mph sustained westerly winds) across southern parts of the Columbia Basin, along the Washington/Oregon border, with a Critical area maintained. Farther east in the Northern Rockies, downslope flow combined with downward momentum transport, should contribute to widespread Elevated conditions (15+ mph sustained westerly winds and 10-25% RH) during the afternoon hours. Locally critical conditions may briefly occur in the most terrain favoring locations, including the Snake River Plain and Great Divide Basin. ...Northern Great Basin into the Central Rockies... With diurnal heating and increasing upper support, isolated to potentially scattered thunderstorm development is expected, especially to the lee of the Sierra in northern Nevada. Storms will be high-based given a deep sub-cloud layer. Training storms and slow storm speeds may allow for some localized appreciable rainfall accumulations, precluding a scattered dry thunderstorm upgrade. Farther east, along the aforementioned band of mid-level moisture, isolated dry thunderstorms are expected as far east as central Wyoming. Aforementioned dry/windy conditions across Wyoming may serve to aggravate fire starts associated with dry strikes. ...Portions of the Southwest CONUS... Guidance continues to indicate widespread Elevated to locally Critical dry/windy surface conditions across southwest portions of the Colorado Plateau, with 15-20 mph sustained southwesterly winds overlapping with 10-20% RH for at least a few hours during the afternoon. The primary negating factor in upgrading to Critical is the lack of more discernible upper-support. ..Squitieri.. 08/11/2020 ...Please see www.spc.noaa.gov/fire for graphic product...Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/fire_wx/fwdy1.html
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