Extended Forecast Discussion NWS Weather Prediction Center College Park MD 342 PM EDT Wed Jun 01 2022 Valid 12Z Sat Jun 04 2022 - 12Z Wed Jun 08 2022 ...Heavy rain threat over Florida due to tropical moisture inflow and a possibly forming tropical system... ...Overview... One notable feature to watch this weekend will be the possibility for a tropical cyclone to develop over the northwestern Caribbean Sea/southeastern Gulf of Mexico partially from energy from what was Agatha in the eastern Pacific (which has now dissipated over Mexico). The National Hurricane Center currently shows a high chance for a tropical cyclone to develop, and its most likely track would be northeastward near or over the Florida Peninsula around Saturday and then deepening as it goes into the western Atlantic. Though the exact timing for development and the track are uncertain, heavy rain will likely impact southern Florida regardless. Farther north, fairly zonal flow is forecast over the lower 48, but with shortwaves and surface frontal boundaries providing foci for thunderstorms and potential for heavy rainfall over much of the central CONUS. ...Model Guidance Evaluation/Preferences... The latest guidance suggests an area of low pressure within an inverted trough moving across southern Florida on Saturday. Notable differences occur between the last several runs of the EC and GFS suites respectively. The EC suite continues to carry a slower closed low that intensifies faster than the other models through the weekend. The GFS suite is faster and farther southeast with the potential tropical surface low center compared to the 00z CMC/EC and latest 12z UK. The EC suite closes off the upper low on Sunday despite the rest of the 12z models remaining generally open throughout the system's lifecycle. The latest guidance remains fairly consistent with upper-level zonal flow, and a shortwave riding across the central U.S. by the middle of next week. The 12z UKMET appears to be an outlier with respect to next Monday's western ridge, as it appears to amplify it a bit more than the 12z GFS and 00z determinstic and ensemble means. Fairly good agreement exists in the Southern lains with the upper ridge next week. The 00z EC appears to be te only model identifying a closed high over Texas/northern Mexico. The 00z EC and 12z GFS are in good agreement as to the timing of the shortwave energy arrival over the Central Plains next Wednesday. Fortunately, the 00z CMCE/ECE and 12z GEFS handle the western ridge and zonal pattern well next week. The 00z and 06z cycles appear to capture a meandering closed upper low, which will be responsible for an atmospheric river event, near the Pacific Northwest fairly well. A general model blend of 00z EC/UK/CMC were utilized with the 06z GFS. The 00z UK carried less weighting thorugh day 5 at which point it was removed. Ensmeble means and the 00z EC and 06z GFS were blended equally by day 7. ...Sensible Weather/Threat Highlights... Regardless of the timing of development of a tropical system, deep tropical moisture is forecast to stream into southern Florida and cause the possibility for heavy rainfall and flash flooding particularly through Saturday, with some possibility of heavy rain in central/northern Florida as well. A Slight Risk is in place in WPC's experimental Day 4 Excessive Rainfall Outlook for the southern Florida Peninsula. Gusty winds could also be a threat if the tropical system develops, with stronger winds for a tropical storm than a tropical depression (by definition). Lingering convergence across South Florida and the Keys could promote additional rain and thunderstorms there through at least the first half of next week. Elsewhere, rain chances are expected to increase in the Northwest into the weekend given the trough axis near the West Coast and moist onshore flow. ARI's in portions of the interior PAC NW suggest an anomalous locally heavy rain possible for that region. However, the Southwest should remain dry and hot, with Death Valley expected to meet or exceed 110F high temperatures this weekend into early next week. Farther east, fronts are expected to spark rounds of showers and thunderstorms across the central and eastern U.S., with parts of the Plains and Mississippi Valley seeing convection over the weekend and early next week as fronts meander there. The axes of enhanced rainfall will be highly dependent on where individual boundaries set up, and it could take into the short range to resolve these differences between models on placement of excessive rainfall, but the ingredients are certainly in place for heavy rainfall in some areas across the central U.S. into early next week. Some showers and thunderstorms could press into the eastern U.S. Monday-Wednesday ahead of a cold front. A relatively flat pattern aloft compared to the somewhat more amplified short range period should produce lesser temperature anomalies this weekend into the first half of next week. Periodic troughing in the northern tier should lead to slightly below average temperatures by around 10F. Meanwhile much of the southern tier can expect above normal temperatures by around 5-10F but reaching +15F anomalies in Texas early next week. The West Coast should be a bit cooler than normal over the weekend under the troughing influence, but moderating and warming to above normal in California by around midweek. Tate/Kebede Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, 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/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml