518 FNUS28 KWNS 012200 FWDD38 Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0458 PM CDT Mon Jun 01 2020 Valid 031200Z - 091200Z A large-scale mid-level ridge is expected to prevail across the CONUS through Day 3/Wednesday, before an upper low, meandering off of the California coastline, merges with a broader trough aloft on Day 4/Thursday and moves across the western CONUS Days 5-6/Friday-Saturday. Thereafter, broad cyclonic flow will persist across the western CONUS, with embedded impulses pivoting around the larger scale trough aloft Days 7-8/Sunday-Monday. Initially, favorable fire weather conditions will remain relatively localized, but with the approach of the aforementioned troughs, the subsequent surface mass response will generate favorably dry and breezy conditions across parts of the Intermountain west supportive of wildfire spread. Deep-layer ascent associated with the cyclonic upper flow pattern will also promote thunderstorm development across portions of the Intermountain West. Elsewhere across the nation, meaningful recent precipitation accumulations, forecast rainfall, non-receptive fuels, or a moistened low-level airmass are expected to preclude large-scale fire weather concerns. ...Days 4-6/Thursday-Saturday... With the approach of the first upper trough, dry and breezy westerly flow is likely across portions of the Great Basin during the afternoon hours Days 4-5/Thursday-Friday. 40% probabilities for critical conditions have been introduced, with the possibility of 70% areas introduced in future outlooks should additional guidance members depict stronger wind fields. Mid-range models diverge somewhat Day 6/Saturday, as the initial trough ejects northeastward, with some members depicting weaker flow aloft and subsequent surface flow across the Great Basin/Four corners area, with other guidance depicting stronger flow aloft and at the surface. Day 6/Saturday critical probability delineations will be withheld until better model consensus is achieved, with probabilities likely introduced pending trends in stronger surface winds. Isolated thunderstorms will be possible across eastern portions of the Great Basin into the Four Corners regions Days 4-6/Thursday-Saturday. Some guidance members depict classic inverted-V soundings extending up to 700-500 mb, indicative of modest dry lightning potential. However, several days of previous, slow moving storms have likely inhibited curing of fuels to a degree, especially in the Four Corners region, where storms will be most likely. 10% isolated dry thunderstorm areas will be withheld until updated fuel guidance become available. ...Days 7-8/Sunday-Monday... As the secondary trough traverses the Internmountain West, widespread dry and breezy surface flow will be possible across the Great Basin, Four Corners, and central Rockies regions. Guidance members however, disagree somewhat on upper trough placement and timing, precluding critical probabilities for favorable surface fire weather conditions until better model agreement is noted. ..Squitieri.. 06/01/2020 ...Please see www.spc.noaa.gov/fire for graphic product... $$
