Extended Forecast Discussion NWS Weather Prediction Center College Park MD 248 AM EDT Tue Apr 12 2022 Valid 12Z Fri Apr 15 2022 - 12Z Tue Apr 19 2022 ...Overview... Lower amplitude flow should dominate the lower 48, at least the first half of the period, behind a departing deep upper low which may linger across eastern Canada into next week. Guidance generally shows a shortwave progressing into/through the West during the weekend and into the Plains/Mississippi Valley by early next week. This feature may produce another round of precipitation over the northern and eastern part of the country. Although there is some agreement with the large scale pattern, there is still plenty of uncertainty with respect to specific system/precipitation details all the way from the West Coast into the East. West coast may get a break for a day or two before the next system approaches next Tuesday. ...Guidance Evaluation/Predictability Assessment... The GFS continues to be a little bit on the faster side with the deep upper low coming out of the Upper Midwest on Friday, as well as a weak low that may track offshore New England. Despite this, a general blend of the deterministic guidance gave a good starting point. The next system enters the west by Saturday, with the GFS/ECMWF a bit faster than the CMC/UKMET. By Sunday-Monday however, uncertainties in the details of this system really ramp up. The GFS has consistently the past few runs been a bit quicker and much flatter/weaker, but also doesn't have great run to run continuity. The ECMWF has presented the best run to run continuity with this system but is also by far the strongest and quickest to develop a rather deep/wound up system over the Midwest states by next Tuesday. The CMC is weaker and flattest with the energy as it comes through the Plains next weekend but it does eventually show a deep closed low across the Midwest like the ECMWF. Confidence is low on any one solution, but regardless it seems likely some sort of low pressure system will move across the central/eastern states late period. Yet another system looks to move into the West next Tuesday, and at this point, models show decent agreement on timing but of course differ in intensity and details. The WPC blend trended towards the ensemble means late period to help mitigate differences. ...Weather Highlights/Threats... The departing low pressure system will likely continue to bring gusty winds into Friday across the northern tier, resulting in blowing a drifting of snow and possible hazardous travel conditions in regions that received heavy snowfall in prior days. Some generally light precipitation should also linger across the Great Lakes/Northeast as well associated with this system. Moisture and instability interacting with a warm front lifting through the Southeast next weekend should bring moderate to locally heavy rainfall to parts of the Southeast/lower Mississippi Valley. Out West, a couple systems may bring rain/mountain snow to parts of the Pacific Northwest and California into the northern Rockies late this week into the weekend. Some of the activity from the West Coast into the Cascades could be moderate to heavy but there is considerable uncertainty over specifics of each system, so confidence is lower than average for determining coverage/timing of the most significant precipitation. Moisture should spread east beyond the Rockies by next Sunday-Monday as low pressure/fronts reach the central/eastern U.S. At least some precipitation across the northern tier may be in the form of snow while rainfall coverage/intensity over the East will depend on currently uncertain system details. The central Rockies/High Plains could see a brief period of strong winds around Sunday with system passage. Expect the core of below normal temperatures to persist across the northern High Plains into early next week, with daytime highs generally 20-30F below normal. Locally colder readings (especially for daytime highs) are possible late this week when some lingering daily records for lows/cold highs are possible. Over the West, temperatures should moderate in between systems as a period of upper ridging moves through. Thursday-Saturday will feature chilly readings over the northern half of the region (minus 10-15F anomalies for highs) and closer to normal temperatures farther south. An upper ridge building over the region by the start of next week should bring northern locations toward normal and southern areas moderately above normal. The East should stay near normal this weekend, but the system potentially reaching the Midwest/East early next week could draw some of the chilly northern Plains air southward and eastward behind it, with expanding coverage of minus 10-20F anomalies. Moderately above normal temps should also shift from the southern Plains into the Southwest/central Great Basin early next week. 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, 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