614 FNUS22 KWNS 161956 FWDDY2 Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Wed Jun 16 2021 Valid 171200Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHERN WYOMING... Expanded the elevated area to include the Snake River Plain based on forecast 15 to 20 mph winds amid less than 10 percent RH. In addition, added a critical area to southern Wyoming. Sustained winds are forecast 25 to 30 mph with gusts as high as 45 mph along the I-80 corridor in southern Wyoming. Guidance regarding fuel receptiveness has been mixed, but recent 1000+ acre fires near the Big Horn mountains in areas showing similar fuel receptiveness lend support for more critical fuels. Therefore, based on this evidence and collaboration with fuels guidance, local WFOs, and regional GACCs, it was deemed fuels are sufficiently dry to warrant a critical delineation. Finally, added an elevated area in northeast Nevada where winds are forecast to be 15 to 20 mph with relative humidity in the single digits. Expanded the isolated dry thunderstorm area westward to include much of southern Nevada into the Sierra and parts of southern California. Lightning may be very isolated across this region, but there appears to be enough of a mid-level moisture push to support at least some convection capable of lightning production. ..Bentley.. 06/16/2021 .PREV DISCUSSION... /ISSUED 0203 AM CDT Wed Jun 16 2021/ ...Synopsis... Strong zonal flow aloft will persist over the northern Rockies into Thursday. This will support strong mid-level winds from Wyoming into Montana and western North Dakota, which will help support areas of elevated fire weather concerns given the receptive fuels. Mid-level moisture will continue to linger across the Four Corners region under an upper-level high, supporting another day of dry thunderstorm potential. ...Northern Rockies and northern High Plains... Westerly surface winds are expected across the northern Rockies and northern High Plains as a surface trough stalls to the east across the Plains and high pressure builds over the Pacific Northwest. Sustained winds near 15-20 mph are probable, and strong mid-level flow may mix down as frequent gusts to 25-35 mph given sufficiently deep boundary-layer mixing. With afternoon RH values in the teens to low twenties expected and receptive fuels already in place, elevated conditions appear likely. Locations along the I-80 corridor in south-central WY will see the highest potential for critical conditions as downslope winds support strong warming/drying as well as wind gusts up to 45 mph. However, recent fuel reports from this area suggest fuels are not as receptive as areas further north, precluding a critical risk delineation at this time (though an upgrade is possible pending new fuel reports). ...Four Corners... A persistent upper-level high over the Four Corners will continue to allow mid-level moisture return from the southern Plains into central AZ, NM, and central CO. Forecast soundings show sufficient instability above deep, well-mixed boundary layers with mean boundary-layer RH values near 20% and PWAT values between 0.4 to 0.6. This suggests a mixture of wet and dry storms is possible, and given recent dry lightning activity under similar thermodynamic conditions in recent days, at least a few dry strikes seem likely. ...Great Basin... Dry conditions will persist across much of the Great Basin for Thursday. Afternoon RH values in the single digits are expected, and fuels will remain receptive after several days of hot/dry conditions. Weak upper-level flow aloft will limit the potential for widespread fire weather concerns, but winds up to 15 mph are possible, especially in terrain-favored locations, which should support patchy elevated conditions. ...Please see www.spc.noaa.gov/fire for graphic product... $$
