892 FNUS28 KWNS 132156 FWDD38 Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0454 PM CDT Tue Apr 13 2021 Valid 151200Z - 211200Z An upper low across the northern Great Basin will move south and intensify through Day3/Thursday before ejecting across the central/southern Rockies as an open wave Day4/Friday. At the surface, low pressure across the southern Great Basin will fill slightly before moving eastward across New Mexico as a cold front and trailing high pressure move south across the central US. Increasing mid-level flow over the Great Basin and southwest will align with dry surface conditions to support increased fire weather potential into early next week. Meanwhile, cooler and wetter than average conditions should limit fire potential over much of the rest of the lower 48. ...Southwest... As the upper-low continues to move southeastward toward the southern Rockies early in the period, mid-level flow will increase substantially as a 70 kt jet ejects eastward. Models soundings across eastern Arizona and western New Mexico show a deep and dry PBL with widespread surface RH ranging from 7-15%. With the increase in flow aloft, and the close proximity to the surface low, winds of 20-25 mph are expected. Widespread dry fuels, low RH, and strong low-level flow will support critical fire weather conditions across the lower and middle elevations through much of the day. Locally elevated fire weather conditions may continue into Day4/Friday across eastern New Mexico and far west Texas as lingering surface flow shifts to the east. RH of 10-15% behind a weak surface trough will likely support some potential through the afternoon before cooler temperatures behind the cold front increase humidity. ...Great Basin... Behind the departing upper-level low Day3/Thursday, winds should remain relatively weak (10-15 mph) with little surface pressure gradient and waning mid-level flow. However, the depth of dry air at the surface with RH near 10-15% should be sufficient for locally elevated fire weather conditions through the day. A shortwave impulse embedded within the northerly flow aloft is expected to intensify as it nears the backside of the upper low drifting onto the High Plains. The weakening surface low is expected to reinvigorate slightly with the approach of the secondary trough. While at the same time, surface high pressure across the central Rockies is expected to increase substantially. The result should be an uptick in low-level northerly winds late Day4/Friday through Day6/Sunday. With dry air in place it appears plausible that some areas of elevated to critical fire weather conditions may develop across the southern Great Basin within this time frame. Though models vary significantly on the strength of the secondary trough and the resulting surface flow. Offshore flow may also spill into portions of southern California with low humidity and near critical winds but confidence in the overall scenario remains low. ...Southeast... Dry post frontal conditions may occur across portions of the Carolinas early this weekend. Winds are expected to be mostly light, but fuels across the area are very dry. Surface RH as low as 20-25% suggests elevated fire weather potential may exist. Some potential for precipitation may limit this threat, though most model projections show little accumulation greater than 0.1 inches. ..Lyons.. 04/13/2021 ...Please see www.spc.noaa.gov/fire for graphic product... $$
