SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Mon Oct 26 2020 Valid 261700Z - 271200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SOUTHERN TRANSVERSE RANGES IN SOUTHERN CALIFORNIA... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF SOUTHERN CALIFORNIA... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF NORTHERN AND CENTRAL CALIFORNIA... ...CRITICAL FIRE WEATHER AREA FOR PARTS OF SOUTHERN NEVADA INTO THE COLORADO RIVER BASIN... Current visible satellite depicts clear skies across California and the Great Basin, allowing for ample boundary-layer heating and continued mixing. As such, near-critical to critically low RH is expected to persist across much of California into the southern Great Basin through the day. Current METAR observations depict 20-30 mph sustained winds, with higher gusts from the Sacramento Valley in northern California, down to the southern Transverse Ranges in southern California and eastward into the Colorado River Basin. In addition, 60-80 kt mid-level flow continues to overspread California into Nevada. Upper support, downslope flow, and downward momentum transport of the stronger mid-level flow will continue to foster strong northerly/offshore flow across portions of the Sacramento/San Joaquin Valleys and the southern Transverse Ranges in California through the day, as also suggested by the latest model guidance consensus. Critical/Extremely Critical Highlights have been maintained across California, although widespread Extremely Critical conditions in the southern Transverse ranges may gradually subside by late afternoon. Critical conditions however, are still expected to persist across southern California into tomorrow morning. At the moment, temperatures are rather cool across parts of southern Nevada, with temperatures in the upper 30s to mid 40s. However, temperatures are expected to warm into the 50s by afternoon peak heating, that combined with continued 25-40 mph sustained northerly flow and 10-25% RH, will foster Critical wildfire-spread conditions through the afternoon. ..Squitieri.. 10/26/2020 .PREV DISCUSSION... /ISSUED 0152 AM CDT Mon Oct 26 2020/ ...Synopsis... A very steep pressure gradient will persist across dry areas of the West and Southwest today in response to 1) very strong high pressure over the western Great Basin and 2) surface troughing from the California coastline southeastward through Arizona and western New Mexico. Additionally, very strong flow aloft will persist across these areas in response to a vigorous mid-level wave expected to be centered over Utah at 12Z and Arizona in the evening. Continued dry fuels and areas of drought will continue to support higher-end fire-weather conditions particularly in portions of California. ...Southern California... Models/high resolution guidance continue to indicate very strong flow across typical, terrain-favored areas of the southern Transverse Ranges throughout the forecast period. Northeasterly surface flow will range from 25-35 mph, with gusts perhaps as high as 70 mph in spots. Meanwhile, very low RH will continue given the dry airmass in place, with 5-15% values becoming common during the day as surface heating commences. Fuels remain dry and favorable for fire spread given continued dry conditions over the past several months. Guidance suggests that these conditions will continue even into the evening hours, owing to poor overnight recoveries and the continued offshore gradient. ...Northern California and the Bay Area... Elevated to critical fire-weather conditions will likely be ongoing at the start of the period as current (05Z-06Z) observations indicate areas of 25-35 mph northerly low-level flow and 7-15% RH values, indicating very poor recovery. The strong surface pressure gradient and favorable upper support suggest that these conditions will continue throughout the day, with RH values remaining low amid surface warming. A few areas may experience gusts to 70 mph. Fuels remain extremely dry/combustible, and a few areas will likely exceed extremely critical thresholds at times - especially in areas between Sacramento and San Francisco/Oakland and including the North Bay Mountains and East Bay Hills. ...Southern Nevada through the Lower Colorado River Valley... Recent high-resolution guidance indicates that enough surface warming will occur for temperatures to reach the 60s F during peak heating hours despite northerly surface flow and modest cold advection. The residing airmass across the region is quite dry, and as temperatures increase, surface RH values will fall into the 5-15% range during the afternoon. Additionally, surface winds will increase into the 25-35 mph range given the surface pressure gradient across the region. Critical fire-weather delineations exist where the aforementioned conditions are most likely to occur amidst dry fuels/fuel beds. ...Please see www.spc.noaa.gov/fire for graphic product...
from SPC Fire Weather Outlooks https://bit.ly/3kybpoH
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