Storm Prediction Center Day 2 Fire Weather Outlook
Created: Mon Dec 4 16:51:02 UTC 2017 ( | )
Click for Day 2 FireWX Areal Outline Product (KWNSPFWFD2)
ZCZC SPCFWDDY2 ALL FNUS22 KWNS 041649 Day 2 Fire Weather Outlook CORR 2 NWS Storm Prediction Center Norman OK 1049 AM CST Mon Dec 04 2017 Valid 051200Z - 061200Z CORRECTED FOR GRAPHIC ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF VENTURA...LOS ANGELES...ORANGE...SAN BERNARDINO...AND RIVERSIDE COUNTIES IN SOUTHERN CALIFORNIA... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA... ...Portions of Southern California... The ongoing forecast is on track and no changes are needed. See discussion below for more details. ...Portions of the Central Plains to Lower MO Valley... Elevated fire weather conditions will extend from portions of the Nebraska Panhandle and northeast Colorado through Kansas and into western Missouri. Very dry air will settle across the region behind a cold front tracking across the region on Day 1/Monday. While high temperatures will be cool, mainly in the 40s to low 50s, deep boundary layer mixing will occur and RH values should fall to around 20-30 percent. An intense mid/upper level jet streak is forecast over Kansas and northern Missouri through much of the day and surface winds will be quite breezy from the west/northwest at 15-25 mph with gusts to 40 mph possible. ..Leitman.. 12/04/2017 .PREV DISCUSSION... /ISSUED 0155 AM CST Mon Dec 04 2017/ ...Synopsis... A large-scale upper trough over the central/eastern CONUS and Ontario will make only slow eastward progress on Day 2/Tuesday. Meanwhile, upper ridging over the eastern Pacific will become prominent across parts of the western CONUS by Tuesday night. At the surface, a broad area of strong high pressure will remain across the northern Rockies and Great Basin, supporting a strong offshore Santa Ana wind event across parts of southern CA. ...Portions of Southern CA... An extremely critical area has been included for parts of Ventura, Los Angeles, Orange, San Bernardino, and Riverside counties in southern CA for Day 2/Tuesday. This is a continuation and expansion of the extremely critical area valid for Day 1/Monday. Across these areas, sustained winds of 30-40 mph will very likely continue through at least Tuesday evening while the surface pressure gradient is maximized. Stronger gusts of 60-80 mph may occur in the higher terrain of these counties given enhanced northeasterly low-level flow that will remain present. These very strong downslope winds will act to warm/dry the low levels, and RH values will likely remain in the 5-10% range for much of Day 2/Tuesday. Fuels will also be very dry and receptive to large fire starts and extreme fire spread given the expected meteorological conditions. Of note, downtown Los Angeles and much of the LA basin have been specifically excluded from the extremely critical area for Day 2/Tuesday, as sustained winds will likely remain somewhat less (generally in the 20-30 mph range) per consensus of latest high-resolution guidance). Regardless, critical conditions are still expected for this major metro area and vicinity. Critical fire weather conditions will occur across a larger portion of southern CA surrounding the extremely critical area. Here, sustained winds of 20-30 mph will be common, with gusts of 45-60 mph likely in the mountains/foothills. RH values of 5-15% will also occur through the period due to continued downslope warming/drying of an already dry airmass. RH recovery late Tuesday into Wednesday morning will likely be very poor as winds will remain strong/gusty across much of southern CA. Consensus of latest guidance indicates the pressure gradient across this region may weaken somewhat from Tuesday night into early Wednesday morning, and wind speeds/gusts may lessen slightly as a result. However, critical fire weather conditions will likely continue across both the critical and extremely critical designations through early Wednesday morning (end of the Day 2/Tuesday period into Day 3/Wednesday). ...Please see www.spc.noaa.gov/fire for graphic product...
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