Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EDT Mon Jun 01 2020 Valid 12Z Thu Jun 04 2020 - 12Z Mon Jun 08 2020 ...A Gulf of Mexico tropical threat and hot temperatures for the west-central U.S... ...Overview and Guidance/Predictability Assessment... The 12/00 UTC ECMWF offer a consistent pattern fit with GEFS/ECMWF ensemble means through day 7 that includes a later week ejection of an EPac/southern CA closed low, northern stream flow amplification and a possible Gulf of Mexico tropical low being followed by NHC/WPC that may threaten the Gulf Coast. The WPC medium range product suite was primarily derived from a composite blend of these guidance sources. The blend tends to mitigate the less predictable smaller scale differences. The 00 UTC GFS has trended more in line with this blend with the potential Gulf low, but uncertainty remains given its complex development. Recent GFS runs and to a lesser extent GEFS runs remain on the faster side of the full solution envelope with the ejection of closed southern CA upper trough. The blocky nature at mid-lower latitudes still seems to favor the slower side of guidance spread for this feature. Overtop, a strong guidance signal indicates that near zonal northern stream flow will significantly amplify by the weekend with development of cooling and unsettling West and East Coast upper troughs. In this pattern, an amplified upper ridge will shift along with hot temperatures from the West/Southwest to the north-central states, settling overtop an emerging west Gulf of Mexico upper low/trough and embedded possible development and slow northward track of a tropical system. ...Weather/Hazard Highlights... Expect showers/thunderstorms will focus some locally heavier downpours Thu from the OH Valley to the central Appalachians/Mid-Atlantic in advance of a southward sinking cold front. Continued southward frontal passage will moderate lead warm sector high heat. The reinforcing front back to the Northern Plains/Rockies will also provide a focus for strong convection through early next week as lead impulses and later period cyclogenesis ahead of the ejecting EPac/southern CA closed upper low enhances local moisture inflow and instability. The hottest temperatures with maximum anomalies of plus 10-15+F and some record values will spread from the West-Southwest to the north-central states ahead of an approaching/moderating cold front. Lead southern CA closed low ejection northeastward over the West late week will increase rainfall coverage and ample West Coast upper trough amplification will further enhance QPF potential from the West/Northwest to the Rockies/northern Plains/Upper Midwest. The Gulf of Mexico should be active with eastern Gulf/FL convection focusing near an old front into late week. WPC/NHC is monitoring potential Gulf system development next weekend into next week that offers a threat to maritime interests and the Gulf Coast. Deep tropical moisture may work gradually northward to significantly enhance rainfall potential. Ryan/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