Extended Forecast Discussion NWS Weather Prediction Center College Park MD 329 AM EDT Tue Jun 02 2020 Valid 12Z Fri Jun 05 2020 - 12Z Tue Jun 09 2020 ...Tropical system to threaten the Gulf Coast and persistent heat over the central U.S... ...Western U.S. heat to give way to much cooler temperatures after Friday... ...Overview and Guidance/Predictability Assessment... Tropical Depression Three is now forecast by the National Hurricane Center to strengthen over the Gulf of Mexico over the next few days and could threaten the Gulf Coast early next week. Guidance spread is extensive with this significant low. Meanwhile, recent GEFS and especially GFS runs remain on the faster side of the full solution envelope with the late week ejection of a closed EPac/southern CA closed upper trough. The blocky nature at mid-lower latitudes seems to still favor the slower side of guidance spread in line with recent ECMWF/ECENS runs. Guidance is in better agreement overall that once ejected, this system will lift ahead of a rapidly amplifying and drastically cooling upper trough digging into the West. Hot upper ridging will accordingly settle over the central U.S. as a downstream upper trough amplifies robustly over the cooling East. This pattern evolution scenario is slated my most guidance to linger from the weekend through early next week. ...Weather/Hazard Highlights... The best potential for highest rainfall totals over the lower 48 during the Fri-Tue period may be along/inland from parts of the central-eastern Gulf Coast depending on the track/timing of the possible Gulf tropical system. A front dropping into the Southeast by Sun-Tue will provide an added focus for moisture, whether from the tropical system itself or carried within the flow to its east. Farther north a leading front should dissipate once it reaches the Mid-Atlantic, followed by the potent front that ultimately reaches the Southeast. Showers and thunderstorms of varying intensity may accompany both fronts. The amplifying upper trough nearing the West Coast and upper low ejecting ahead of it will promote one or more episodes of locally enhanced precipitation over portions of the Northwest and some other locations extending into the northern-central Rockies. By the start of next week the arriving upper trough may be deep enough to support a little snow at the highest elevations of the Northwest. Locally strong/heavy convection will be possible over parts of the Northern Plains/Upper Midwest with the combination of western impulses rounding the upper ridge/cyclogenesis and interaction with the trailing part of the reinforcing eastern U.S. cold front. High heat will extend over the West through Fri, with some plus 10-15+F anomalies. Then the arriving upper trough will bring a pronounced cooling trend, leading to highs up to 10-15F below normal over the West Coast states, spreading to the Great Basin then Rockies by early next week. The most persistent area of well above normal temperatures will be downstream over the central U.S. In particular, the south-central High Plains should have highs 15+F above normal late week into the weekend. A sizable area of plus 5-15F anomalies should continue over the Plains into early next week. Over the East, the pattern will moderate from short range heat as cool high pressure builds in behind the second front. Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml