Storm Prediction Center Day 1 Fire Weather Outlook
Created: Sun Oct 27 06:18:02 UTC 2019 ( | )
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ZCZC SPCFWDDY1 ALL FNUS21 KWNS 270616 Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0116 AM CDT Sun Oct 27 2019 Valid 271200Z - 281200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE NORTHERN BAY AREA... ...CRITICAL FIRE WEATHER AREA FOR MUCH OF THE NORTHERN AND CENTRAL SACRAMENTO VALLEY... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA... ...CRITICAL FIRE WEATHER AREA FOR SOUTHEAST ARIZONA... ...Synopsis... Potentially historic fire weather conditions are expected in the northern Bay Area today. A sharp, positively tilted trough with an associated strong mid-level jet streak will move southward across California today. At the surface, strong area of high pressure has built into the northern Rockies with additional strengthening of the surface high expected as it moves southward toward the Great Basin. The strong pressure gradient between this high and the area of low pressure off the California coast will lead to fire weather concerns across portions of northern California, southern California, and the Colorado River Valley. In addition, elevated fire weather conditions will be present near the Four Corners Region. ...Most of the Sacramento Valley and the northern Bay Area... A strong northerly pressure gradient is already present early this morning with a MFR-RDD pressure gradient around 13 to 14 mb. This has resulted in numerous observation sites reporting critical fire weather conditions in the northern Sacramento Valley. These stronger winds and dry air will continue to move south across northern California through the early morning hours. Winds will start to strengthen across Napa, Lake, and Solano counties around 08Z to 09Z. Winds will continue to strengthen and relative humidity drop throughout the day as downslope flow intensifies. The peak winds are expected between 16Z and 22Z. During this period, upper-level support will assist low-level winds as mid-level flow is around 80 knots out of the north northeast and 1km flow is around 50 knots. Therefore, widespread 35 to 50 mph winds with gusts to 65 mph are expected across Colusa, Napa, Lake, Yolo, and eastern Sonoma counties. Locally higher wind speeds around 40 to 55 mph with gusts to 75 mph are possible in the higher terrain. ERC values across the area are above the 85th percentile with some localized areas of near record high ERC. Therefore, fuels across the region will be plenty supportive of extreme fire spread given the conditions. Additionally, the presence of a large fire (Kincade fire) within the area that is expected to see extremely critical fire weather conditions today increases concern for extreme impacts from this fire weather event. The most extreme winds should weaken by late afternoon and into the evening, but continued offshore flow should keep critical fire weather conditions across the area through the overnight and into the early morning hours Monday. ...Portions of Southern California... A moderate to locally strong Santa Ana event is expected in southern California starting Sunday evening and persisting through Monday. The LAX-DAG pressure gradient is expected to peak around 15 to 18Z Monday. Wind speeds early Monday morning are expected to be around 25 to 35 mph with gusts to 55 mph in the mountains of Los Angeles and Ventura counties with dewpoints dropping into the single digits. Strongly considered a small extremely critical delineation for portions of the higher terrain in Los Angeles and Ventura counties. However, after collaboration with the local office in Oxnard, decided to keep the category at critical for Day 1 considering the threat for extremely critical conditions will be limited to the final few hours of the Day 1 period. ...The Colorado River Valley... Any fuels which are present in the Colorado River Valley are likely well irrigated, however, winds of 20 to 30 mph and relative humidity around 10 to 15 percent raise enough concern about fire weather conditions to warrant an elevated delineation. ...Southern Arizona into the Four Corners Region... Moderate to strong mid-level flow is expected to overspread the Southwest on Sunday. Dry surface conditions will be in place with relative humidity around 13 to 20 percent. Deep mixing during the afternoon hours will transport some of these stronger winds toward the surface. Sustained surface winds of 35 to 40 mph are expected across a large part of the Four Corners region. Despite the meteorological conditions supporting a critical delineation, sparse fuels across the region reduce the threat for large fires significantly, and thus, an elevated delineation should be sufficient to cover the threat. In addition, farther south, wind speeds of 20 to 30 mph are expected during the peak heating during the afternoon with relative humidity around 12 to 20 percent. Several smoke plumes could be seen this afternoon in the higher terrain in central and eastern Arizona. These fires could spread rapidly Sunday afternoon given the strength of the winds. ..Bentley.. 10/27/2019 ...Please see www.spc.noaa.gov/fire for graphic product...
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