Extended Forecast Discussion NWS Weather Prediction Center College Park MD 255 AM EDT Fri Jun 05 2020 Valid 12Z Mon Jun 08 2020 - 12Z Fri Jun 12 2020 ...Lower Mississippi Valley Heavy Rainfall Threat early next week from Cristobal... ...Overview... Amplified pattern will continue through next week as Cristobal moves inland over the northern/northwest Gulf Coast Monday. A strong upper trough is forecast to exit the Rockies and help guide the remnants of Cristobal to the north/northeast as ridging gets squeezed into the Northeast. Off the East Coast, a trough will likely split off an upper low that may get wrapped back toward the Mid-Atlantic/Northeast as the "ex-Cristobal"-containing front heads to the coast. Another upper low will spill out of the Gulf of Alaska later in the week. ...Guidance/Predictability Assessment... The guidance shifted a bit southwestward with the initial track of Cristobal through southern Louisiana (per the latest forecast -- please consult the National Hurricane Center for the most recent information) and will likely continue to shift until the system becomes better organized. For now, followed a middle solution with the NHC track. How quickly Cristobal moves northward (and at what longitude) will modulate how it interacts and gets absorbed into the front approaching from the northwest. Again, consensus approach was most prudent given lead-in uncertainties--between the quicker ECMWF ensembles and slower GEFS ensembles with respect to the exiting trough from the Rockies Tue. Once the system becomes absorbed around Wednesday, buckling pattern forecast by the ensembles suggests continued uncertainty in the depth of each system. Favored the ECMWF and its ensembles over the GFS/GEFS ensembles by about 3:1 given the former's consistency and tendency for better accuracy in amplified flow. ...Weather/Hazard Highlights... Deep trough Mon over the Rockies will support cold temperatures and snow at higher elevations (Glacier Nat'l Park and Yellowstone) with continued heat over the Ohio Valley ahead of the front/Cristobal. Rainfall may be enhanced along/ahead of the front over/east of the Plains into the Upper Midwest and just ahead of Cristobal as moisture axes interact/combine ahead of a 100kt jet. By later in the week, rainfall amounts may decrease as the moisture source gets thinned and high pressure builds in from the northwest. Lighter rain is forecast for the Pacific Northwest through the week. Temperatures will be chilly to start the week over the Great Basin and Northern/Central Rockies (10-20 degrees below normal) but will rebound back to above normal by Thu/Fri (about +5 to +10 anomalies). Warm temperatures in the Upper Midwest/Ohio Valley will progress eastward into the Northeast Tue/Wed to be replaced by typical early June values in the mid 70s to low 80s as the lead and secondary cold fronts approach. Much cooler temperatures will be behind the second front with high temperatures only in the 60s for areas around the western Lakes. Fracasso 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