Extended Forecast Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Sun May 26 2024 Valid 12Z Wed May 29 2024 - 12Z Sun Jun 02 2024 ...General Overview... The upper level pattern across the continental U.S. will be featured with a trough over the Pacific Northwest, a ridge over the Northern Plains, and a trough over the Great Lakes for the beginning of the forecast period Wednesday. Both of these troughs move rather slowly eastward through the end of the week, while the southern tier states have more zonal flow aloft. The trough crossing the Rockies will be accompanied with a surge of moisture from the Gulf of Mexico ahead of an approaching cold front, and this will fuel multiple rounds of heavy rain and thunderstorms across the Plains for the second half of the work week. The trough then reaches the Upper Midwest by next weekend while the upper ridge tries to rebuild across Texas. ...Guidance/Predictability Assessment... The 00Z model guidance suite maintains good overall agreement on the synoptic scale for the middle of the week. The main difference noted is with the UKMET that has been much more progressive with the Pacific Northwest trough moving inland over the past few runs. Therefore, the model blend consisted of the CMC/ECMWF/GFS along with some previous WPC continuity through Thursday. Looking ahead to next weekend, the 12Z ECMWF appeared much stronger with the trough crossing the Upper Midwest compared to the model consensus at the time of fronts/pressures generation. Upon examination of the machine learning guidance, there was not much support for the more amplified ECMWF solution, so preference was given to the broader CMC/GFS/GEFS mean for Saturday and Sunday. Interestingly, the GFS trended stronger by next Sunday with this same trough, whereas the ECMWF became less amplified compared to its 12Z run and more in line with the ML guidance. Ensemble means accounted for about 40-50% of the forecast blend by next weekend. ...Weather/Hazards Highlights... Numerous showers and thunderstorms are likely across much of the central and southern Plains going into the second half of the work week as a warm front lifts up from the western Gulf and advects copious moisture northward. This will also be in tandem with increasing lift afforded by an incoming upper trough from the Rockies. A broad Marginal Risk area is planned for the new Day 4 period Wednesday from eastern Colorado to the Texas Gulf coast, and a Slight Risk area across portions of north-central Texas and into southwestern Oklahoma on Thursday where MCS activity is most likely to develop. Additional heavy rain is expected on Friday across much of Kansas and into Oklahoma and northern Texas with the overall weather pattern not changing all that much. Some strong to severe thunderstorms are also likely. The potential exists for 3-5 inches of rainfall through late Friday for some of these areas that get repeated rounds of convection. Hot and humid conditions are expected to continue across much of the Gulf Coast region, including the Florida Peninsula, going into the end of the week, but a few degrees cooler compared to what is happening now. This will equate to highs in the upper 80s to middle 90s for these areas, and low-mid 100s for interior portions of southern Texas. The opposite will hold true from the Great Lakes to the Mid-Atlantic and Northeast as a relatively strong cold front heralds the arrival of a high quality airmass with pleasantly cool conditions and lower humidity to close out the week. There will likely be some showers across the northeastern quadrant of the nation in conjunction with the trough/upper low that passes through the region. Cooler weather is also expected from the Pacific Northwest to the Northern Rockies courtesy of the upper trough moving overhead, and then a return to warmer conditions for much of the Western U.S. by next Sunday. Hamrick 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 forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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 https://www.wpc.ncep.noaa.gov/#page=ovw