Administrators NorthGeorgiaWX Posted September 29 Administrators Share Posted September 29 SPC Day 1 Fire Weather Outlook Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1034 AM CDT Sun Sep 29 2024 Valid 291700Z - 301200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST NEBRASKA INTO SOUTHERN NORTH DAKOTA... ...CRITICAL FIRE WEATHER AREA FOR CENTRAL WYOMING... ...Northern Rockies/Plains... The primary adjustment for this update is introducing a Critical risk area to parts of central WY where morning guidance has come into reasonably good agreement in a few hours of sustained 20-25 mph winds with RH values near 15%. Additionally, the Elevated risk areas across the northern Rockies and northern Plains have been combined and expanded into eastern MT to account for two trends. First, morning surface observations are drier/windier along the surface trough that is in place across the High Plains than previously anticipated by guidance. This trend suggests that elevated to critical fire weather conditions may be more pervasive than depicted by the previous outlook. Second, dry and windy conditions are likely overnight tonight as a dry cold front pushes southeast across MT and the western Dakotas. An influx of dry air will limit nocturnal RH recovery with most 12z guidance suggesting that 15-25% RH and 20-30 mph winds will be common for a few hours in the post-frontal regime. ...Utah... Very isolated thunderstorms are expected this afternoon across central UT. The 12z SLC sounding sampled very dry boundary-layer conditions, but cold temperatures aloft with adequate moisture for weak convection. Additionally, recent visible imagery already shows shallow cumulus developing atop the boundary layer. As such, a few dry thunderstorms appear possible and may overlap with the dry fuels that are in place across west-central UT. However, thunderstorm development appears most probable across central UT where orographic ascent will bolster the relatively weak ascent over the region. Given the low probability for dry lightning over receptive fuels, additional risk highlights were withheld. ..Moore.. 09/29/2024 .PREV DISCUSSION... /ISSUED 1228 AM CDT Sun Sep 29 2024/ ...Synopsis... Elevated to critical fire-weather conditions are expected across much of the Intermountain West into the northern Great Plains as a progressive mid-level trough traverses the Canadian prairies. The deepening surface cyclone and tightening surface pressure gradients associated with this trough will result in widespread dry and windy conditions over receptive fuels. A narrow Critical area has been maintained where the highest confidence in 20-25 MPH winds and relative humidity values below 15% are expected to overlap with ERC fuels exceeding the 95th annual percentiles. Portions of central and eastern Wyoming may also experience locally critical conditions, though confidence in the magnitude and spatial extent of surface winds precludes Critical highlights at this time. Further west, elevated fire-weather conditions are expected across central and eastern Nevada into western Utah, as well as portions of Columbia River Basin in Washington. Winds in the Columbia River Basin could be as high as 20-25 MPH, but forecast guidance shows significant spread in the forecast boundary-layer relative humidity values (15-25%). Across the Great Basin, winds will generally remain in the 15-20 MPH range with relative humidity values of 10-15%. ...Please see www.spc.noaa.gov/fire for graphic product... Read more View the full article Quote Link to comment Share on other sites More sharing options...
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