Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Sat Apr 23 2022 Valid 12Z Tue Apr 26 2022 - 12Z Sat Apr 30 2022 ...Overview... An upper trough digging into the northern tier and toward the Midwest/Ohio Valley will steadily push a cold front through the Eastern Seaboard where generally modest rainfall is expected on Tuesday. Modest cyclogenesis forecast to occur near/east of New England will likely promote lingering precipitation for the Northeast as the week progresses. Meanwhile, mean troughing is likely in the West with multiple shortwaves tracking through, bringing periods of precipitation while ridging in between will spread warm temperatures from the Southwest to southern/central Plains by late week. ...Model Guidance Evaluation... Model guidance has remained consistent with better than average agreement for the above-mentioned pattern at least through Day 5/6. The GFS and GEFS continues to show a tendency for a faster exit of the low off to the east of New England later next week than the ECMWF and CMC. The same tendency generally applies to the mean trough in the West. A shortwave reaching the Northwest around Tuesday should continue onward across the Canadian Rockies, possibly forming a compact upper low over Albert midweek with the GFS being the most prominent and fastest with this feature. This faster eastward progression of the upper low in the GFS promotes earlier cyclogenesis to occur over the central Plains toward the upper Midwest late week than in the ECMWF and CMC solutions. Given the relatively typical model biases as discussed above, the WPC medium-range forecasts were based on a multi-model consensus of 40% from the 00Z ECMWF/00Z EC mean, 40% from the 06Z GFS/GEFS, and 20% from the 00Z CMC/CMC mean. Only a larger weight toward the ensemble means was applied to mitigate the higher uncertainty on Day 7. The results were very compatible with the previous forecast package. ...Sensible Weather/Threats... The cold front moving across the Eastern Seaboard as the period begins on Tuesday will promote rain and possibly thunderstorms along it. Its reasonably fast progression should keep rainfall amounts in the light to moderate range. Then as surface low pressure consolidates and pivots around the upper low, precipitation will remain in the forecast across the Northeast through the end of the workweek. There is some potential for higher elevations of New England to receive snow with this precipitation activity. Precipitation do not appear to be particularly heavy at this time but will be monitored due to its lingering tendency. Meanwhile in the West, unsettled weather is likely as shortwave energy moves through the mean trough south of a closed upper low positioned off British Columbia through Thursday. Guidance has continued to indicate an episode of rain and high elevation snow Tuesday-Wednesday from the Pacific Northwest to the northern Rockies associated with the shortwave energy, which will be followed by another episode late week in the same general vicinity as the main trough/upper low pushes onshore. By Friday, a general expansion of rain is forecast for the northern to central Plains spreading toward the Midwest and the Ohio Valley into Saturday as a low pressure system is forecast to develop over the central Plains. The fast GFS solution is not preferred at this point. Meanwhile, some form of wintry precipitation is forecast for the northern High Plains into North Dakota on Friday. The core of post-frontal cold air is forecast in the Dakotas/Midwest on Tuesday and spreading into the Great Lakes region by Wednesday-Thursday, with temperatures 10-25F below average. As the cold front sweeps across the East, temperatures will transition from warmer than normal on Tuesday to below normal midweek, though with some temperature moderation. The Northwest should see near to slightly below average temperatures, but by late week temperatures in the northern Rockies/Plains is forecast to cool down to much below normal levels especially in terms of highs with the possibility of more potent troughing aloft. Meanwhile farther south, ridging in place will spread warmer than normal temperatures from the Southwest/Four Corners states into northern and central parts of the Plains, with afternoon temperatures soaring into the 90s in many areas ahead of the developing low pressure system. Kong/Tate/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, 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