Extended Forecast Discussion NWS Weather Prediction Center College Park MD 257 AM EDT Mon May 27 2024 Valid 12Z Thu May 30 2024 - 12Z Mon Jun 03 2024 ...General Overview... The upper level pattern across the continental U.S. will be featured with a trough over the Northern Rockies, a ridge over the Upper Midwest, and a trough over the Northeast U.S. for the beginning of the forecast period Thursday. Both of these troughs move rather slowly eastward through Saturday, 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 frontal boundary, and this will fuel multiple rounds of heavy rain and thunderstorms from northern Texas to the central Plains for the second half of the work week. The trough then reaches the Upper Midwest by next weekend and then lifts northward into Canada, while the upper ridge rebuilds across Texas late in the forecast period. ...Guidance/Predictability Assessment... The 00Z model guidance suite is in good overall synoptic scale agreement for Thursday and Friday, even though the UKMET is still a little more progressive with the trough exiting the Rockies to the Northern Plains. The UKMET is now closer to the consensus compared to previous runs when it was much faster than the other guidance. The GFS is now slower with the passage of the other trough across the East Coast compared to the consensus, but matches up pretty well elsewhere through Friday. A multi-deterministic model blend, with slightly less weighting to the UKMET, sufficed as a starting point in the forecast process through the end of the week. Looking ahead to next weekend, the GFS becomes stronger with a second trough developing across the north-central U.S. that does not currently have much support from the other guidance, and this remains the case going into next Monday. The CMC is the faster solution with the next trough approaching the Pacific Northwest by Monday. There is good overall agreement that the upper ridge will build back across Texas by this time as well. Ensemble means accounted for 30-50% of the forecast blend by Sunday-Monday. ...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 Thursday from central Texas to the eastern Dakota, with a Slight Risk remaining in place over north-central Texas and into southern Oklahoma, where MCS activity is most likely to develop. Additional heavy rain is expected on Friday across many of these same areas with the overall weather pattern not changing all that much, with a broad Day 5 Marginal Risk area planned from northern Texas to the Upper Midwest. There will likely be the need for a Slight Risk area during this time in future updates, but the differences in QPF maxima among the guidance preclude having any Slights at this time. 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