Extended Forecast Discussion NWS Weather Prediction Center College Park MD 456 PM EDT Tue Mar 31 2020 Valid 12Z Fri Apr 03 2020 - 12Z Tue Apr 07 2020 ...Overview and Guidance/Predictability Assessment... Guidance generally shows varying degrees of mean ridging from the northwestern Caribbean/Gulf of Mexico through much of eastern North America into northern Canada, while upper troughing prevails over the western part of the continent/West Coast. Flow around the south side of a broad upper low initially over western Canada will cross the northern tier states, bringing a front into the East. One Pacific impulse should reach near the West Coast around early Sat and quickly eject inland, followed by a deeper and slower system by Sun-Mon. Guidance agrees fairly well for significant features during days 3-4 Fri-Sat, allowing for an operational model blend to represent consensus well. Day 5 Sun exhibits some spread/trending for the trough and possible embedded upper low nearing the West Coast. Through the 00Z/06Z cycles the CMC/UKMET tracked the upper low somewhat farther offshore than other solutions, while the majority cluster has adjusted the core of the trough a bit southward. Ultimately the multi-model blend was good for depicting this southward trend while leaning away from the 00Z CMC/UKMET specifics. Note that through Sun the new 12Z CMC/UKMET are closer to the consensus while the 12Z GFS has trended south of previous runs. In contrast, the new 12Z ECMWF carries the core of the upper trough north of its 00Z run. The ultimate progression of this feature after early Sun depends upon its exact path up to that point and then influence from increasingly uncertain upstream flow over the northeastern Pacific. Differences among individual ensemble members as well as consecutive operational model runs from the past couple days highlight the low confidence in northeastern Pacific details. Based on data through the 06Z cycle, preferred to side with the 06Z GEFS/00Z ECMWF means and 00Z ECMWF which were in the middle of the spread for trough progression. The 00Z/06Z GFS became quite fast to eject the trough into the Plains while the latest CMC runs stray to the slow side of the spread (albeit not much slower than the new 12Z GEFS mean). The 12Z GFS shows a favorable trend, slower than the 06Z run by 12-24 hours by next Tue. ...Weather/Hazard Highlights... Expect a large portion of the West to see at least some rain and high elevation snow during the Fri-Tue period, with the Desert Southwest and southern Rockies having the best possibility of staying mostly dry. The first Pacific system will be fairly compact and bring the best precipitation focus to northern California and vicinity with some moisture extending to the northern Rockies. The second system will likely bring highest totals to northern California/Sierra Nevada and spread a larger shield of precipitation across the West, possibly as far south as the coastal ranges of southern California. Depending on exact tracks of these systems, southwestern Oregon could receive significant precip as well. A front pushing across the Plains and east-central U.S. late this week/early weekend will focus an axis of mostly rainfall, including the potential for some locally heavy activity over and possibly east of Texas. Sufficiently cold air may exist to promote some snow over Minnesota/extreme northwest Wisconsin around Fri. With time expect the precipitation along the front to become lighter and more scattered especially across northern parts of the East. Another area of rainfall may develop across the eastern half of the country late weekend into next week with the best signal for some significant totals extending from the Southern Plains into the Tennessee Valley. Other areas could see enhanced activity as well but with lower confidence. Cold air behind the late week Plains/Mississippi Valley front will bring temperature anomalies down to 10-25F below normal over the northern-central Rockies/Plains on Fri, followed by a warming trend. The overall pattern aloft will tend to favor moderately below normal readings west of the Rockies during the period. Minus 5-10F or so anomalies for highs should be most common over California/Nevada early next week. On the other hand above normal temperatures will become more expansive to the east of the Rockies. By next Mon-Tue expect broad coverage of at least plus 10-20F anomalies, with morning lows tending to be somewhat more extreme versus normal than the daytime highs. Rausch Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy rain across portions of the Southern Plains, Tue-Wed, Mar 3-Mar 4. - Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Wed-Thu, Mar 4-Mar 5. - Heavy snow across portions of the Central Great Basin, California, and the Southwest, Sat-Tue, Apr 4-Apr 7. - Flooding possible across portions of the Middle Mississippi Valley, the Great Lakes, the Upper Mississippi Valley, and the Northern Plains. - Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Northern Plains, the Tennessee Valley, the Middle Mississippi Valley, the Upper Mississippi Valley, the Southern Plains, and the Ohio Valley. - Flooding likely across portions of the Great Lakes, the Middle Mississippi Valley, the Southern Plains, the Upper Mississippi Valley, and the Northern Plains. - Much below normal temperatures across portions of the Central Plains, the Northern Plains, and the Northern Rockies, Fri, Apr 3. WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml