Storm Prediction Center Day 1 Fire Weather Outlook
Created: Sat Aug 19 16:42:03 UTC 2017 ( | )
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ZCZC SPCFWDDY1 ALL FNUS21 KWNS 191640 Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1140 AM CDT Sat Aug 19 2017 Valid 191700Z - 201200Z No changes have been made to the existing elevated areas. Across portions of eastern MT/western ND, elevated conditions are already being observed at some locations and these conditions will persist through the afternoon. Critical RH/wind criteria may be reached concurrently for a brief period this afternoon, but the potential for a sufficient duration of critical conditions at any given location appears too limited for an upgrade. Further west, elevated to locally critical conditions still appear likely across portions of ID/southwest MT/WY, and also across portions of northern CA/southwest OR. See the previous discussion below for additional information. ..Dean.. 08/19/2017 .PREV DISCUSSION... /ISSUED 0144 AM CDT Sat Aug 19 2017/ ...Synopsis... An upper trough over AB/SK will progress eastward towards MB today. 30-40 kt of mid-level westerly winds attendant to this upper trough will overspread eastern MT into ND by this afternoon. At the surface, a low over southern SK will also develop eastward into MB by this evening, with a trailing cold front advancing southeastward across the northern Plains. ...Portions of the Northern Great Basin into the Northern/Central Rockies and Northern Plains... Strong/gusty low-level winds should develop both along and ahead of the surface cold front this afternoon across eastern MT into western ND and northwestern SD. Short-term guidance shows sustained west-northwesterly winds of 15-20 mph occurring in conjunction with RH values lowering into the 15-25% range with diurnal heating of a relatively dry boundary layer, supporting an elevated fire weather threat. RH values are forecast to increase behind the front, although strong surface winds approaching 20 mph and veering to northwesterly may allow for continued elevated fire weather concerns into the evening hours. Locally critical conditions may be realized briefly across a small part of the elevated delineation, but confidence in widespread winds in excess of 20 mph remains too low to include a critical area. Elevated fire weather conditions should also develop this afternoon across part of the northern Great Basin into portions of the northern/central Rockies, as the southern fringe of enhanced mid-level westerlies overlies this region. Localized enhancement to the low-level winds appears likely across part of the Snake River Valley and vicinity into western/southern WY, with sustained west-southwesterly winds of 15-20 mph combining with RH values of 10-20% and dry fuels to support an elevated fire weather threat. The lack of even stronger forecast low-level flow precludes a critical designation across this region. ...Southwestern OR/Northern CA... A strengthening surface pressure gradient to the west of the Cascades will encourage increasing northeasterly to northwesterly winds across southwestern OR/northern CA this afternoon and evening. Sustained winds of 15-20 mph appear likely at lower elevations, with stronger gusts possible at mid/high elevations. RH values will easily lower into the 15-25% range by afternoon given the dry airmass in place, and overnight RH recovery is expected to remain poor, particularly at higher elevations. This expected combination of strong/gusty winds with lowered RH values, very dry fuels, and numerous ongoing large fires necessitates the introduction of an elevated area across this region. ...Please see www.spc.noaa.gov/fire for graphic product...
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