Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 PM EDT Tue Mar 22 2022 Valid 12Z Fri Mar 25 2022 - 12Z Tue Mar 29 2022 ...Overview... An amplified upper level pattern is expected to prevail through the medium range period as a ridge begins to build over the western U.S. while a broad trough in the eastern U.S. will be reinforced and possibly amplified by intrusions of colder air from central/eastern Canada. A general cooling and drying trend is expected across the Northeast as potentially record-setting warmth in the West spreads eastward into the High Plains by early next week. The most uncertain aspect in the pattern will likely be off the West Coast where the timing and amplitude of a trough or potentially closed low will affect when and if any significant precipitation will move onshore for early next week. Despite the uncertain with the timing of the West Coast trough, model ensemble means indicate decent agreement for a surface low pressure system to develop in the central Plains by next Tuesday. ...Guidance Evaluation/Predictability Assessment... Model guidance this morning begins with generally good agreement on slowly pulling out the low pressure system off New England on Friday and into the weekend. Meanwhile, a clipper system is forecast to move across the northern Plains and interact with the departing low pressure system over new England. Models continue to indicate some difficulties in timing this interaction, resulting in uncertainty on the subsequent details of the trough amplification as well as the positions surface fronts over the eastern U.S. There is some potential for modest cyclogenesis to occur just off the New England coast by about Sunday. Over the western U.S., models are in general agreement with a ridge building across the region. In contrast, much uncertainty lies off the West Coast where an upper trough is forecast to amplify. Models show considerable uncertainty on the subsequent evolution of this trough. The GFS and CMC maintain that this feature will move into the western U.S. early next week. The recent couple of runs of ECMWF, however, have abandoned this scenario by closing off this trough and digs it southward well off the West Coast. This scenario is possible given the increasingly high amplitude nature of the pattern by the weekend. Nevertheless, the 00Z EC mean appears at odds with the EC deterministic by forming a low pressure system over central Plains next Tuesday in agreement with the GFS and CMC, which would imply a faster progression of the trough through the western U.S. Thus the WPC medium-range package was based on the consensus of the 00Z ECMWF/EC mean and the 06Z GFS/GEFS mean, with increasing usage of the ensemble means by Day 5. A small contribution of the 00Z CMC was included for Days 3-4 followed by a small amount from the CMC mean Days 5-7. The results are reasonably compatible with WPC continuity except the timing of low pressure waves off the West Coast. ...Weather Highlights/Threats... Snow is forecast to linger in Maine on Friday as a low pressure center slowly exits New England. Then shortwave energy and weak low pressure/frontal systems are expected to produce light precipitation as they move across the Great Lakes region to the central/northern Appalachians and Northeast late week into the weekend. Some of the precipitation will be in the form of snow in higher elevations and northern latitudes, and gusty winds are also possible. Precipitation ahead of the approaching eastern Pacific upper trough is likely to reach the Pacific Northwest around Friday and then spread across more of the West thereafter. Most of this activity should be in the light to moderate range but some locally heavier totals could be possible depending on the uncertain timing of system details. Coverage and intensity of this precipitation becomes more uncertain by late weekend into early next week. Unseasonably warm temperatures will build and expand underneath upper ridging from the western U.S. into the Plains. Highs that are 10-20F above normal will be common over California and the Great Basin/Southwest Friday, with some plus 20-25F anomalies appearing in the Great Basin Saturday and moving to the northern/central High Plains early next week as the upper ridge axis shifts. Daily record temperatures could be tied or set across California and eastward. Temperatures in the West are likely to cool closer to normal by around Monday but the exact timing will depend on the trough's movement inland. Meanwhile the East should see near to slightly below average temperatures given mean upper troughing, with coolest temperatures of 10-15F below normal in the central Appalachians for the weekend and in the Great Lakes early next week. Kong/Tate 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 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml