Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Fri Mar 21 2025 Valid 12Z Mon Mar 24 2025 - 12Z Fri Mar 28 2025 ...Overview... The early to middle part of next week will feature a large-scale western U.S. upper ridge and eastern trough. The pattern should flatten/progress some later in the week, as energy from an eastern Pacific trough reaches into the West while the ridge moves into the Plains/Mississippi Valley and the eastern troughing begins to lift out. Expect very warm temperatures under the upper ridge with some daily records possible over the West. The Great Lakes and East Coast/Gulf Coast will see one episode of precipitation with a Monday system with a possible Midwest wave on Tuesday potentially spreading some moisture into the East by midweek. The upper dynamics and leading front reaching the West will bring rain and high elevation snow to the Northwest mid-late week. Meanwhile a southern tier shortwave will bring a threat of locally heavy rainfall to parts of the southern half of Texas late in the week. ...Guidance/Predictability Assessment... Models and ensembles show good agreement on the large scale, but still a lot of uncertainty in the details. There is good consistency with the Eastern U.S. system on Monday-Tuesday, but still spread with the next wave into the Midwest and towards the Northeast. This second feature though has fairly low predictability due to being very sensitive to small scale detail differences in supporting shortwave energy. By mid to late week, some continued spread as the next trough enters the West. Overnight ECMWF runs were sharper than previous runs (and other guidance), so did not put much weight on that solution in the blend today. CMC/ECMWF runs are also faster than the GFS with the trough. WPC blend for today favored the deterministic models early period, trending towards slight majority ensemble means later in the period. This maintained good continuity with previous WPC forecasts as well. ...Weather/Hazards Highlights... Low pressure tracking from the Great Lakes eastward early in the week will produce some snow over far northern areas, with best potential for meaningful accumulation on Monday over central and northern New England. Expect rain farther south along the trailing cold front. The Day 4/Monday Excessive Rainfall Outlook holds onto a Marginal Risk area over parts of the Gulf Coast in light of lingering training potential that is most prominently suggested in the GFS. However other guidance is less enthusiastic QPF-wise and it is a fairly progressive front, so would consider this a lower- end threat at this time. Behind this system a weak wave may track through the Midwest around Tuesday and then near the Northeast coast by Wednesday. Any associated precipitation should be fairly light and confidence in the system's evolution is below average at this time. Far northern parts of the West may see lingering precipitation on Monday with most of the region dry by Tuesday. Upper trough energy and a leading cold front will bring another round of rain and high elevation snow into the Northwest and northern Rockies mid-late week. There is some uncertainty over amounts and south and inland extent. Around Tuesday-Tuesday night some guidance hints at the potential for very localized enhanced rainfall over parts of the southern Plains, near the front trailing from the weak Midwest wave. This potential activity is not sufficiently agreeable or organized in the guidance to merit an ERO risk area at this time. Ground conditions are also fairly dry over this region. Then the combination of an approaching southern stream trough along with moist easterly low level flow from the Gulf may increase the chances for more organized and heavier rainfall over parts of southern Texas late in the week. The strong upper ridge over the West early-mid week will bring well above normal temperatures to the region, with a broad area of highs 10-20F above normal with locally higher anomalies. There will also be potential for numerous daily records for highs/warm lows, especially on Tuesday and Wednesday. Some places over the Desert Southwest could get close to 100 degrees. As the upper pattern shifts eastward somewhat later in the week, the West will cool down while already above normal anomalies over the central U.S. will increase. Areas over and near the central Plains should see highs reach 20-25F above normal by Thursday-Friday. Mean troughing aloft will keep most of the East near to slightly below normal for temperatures. Santorelli/Rausch 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