Extended Forecast Discussion NWS Weather Prediction Center College Park MD 441 PM EDT Thu Mar 17 2022 Valid 12Z Sun Mar 20 2022 - 12Z Thu Mar 24 2022 ...Strong low pressure system will likely produce heavy rain/severe storms across portions of the southern U.S. and heavy central Rockies snow by early next week... ...Overview... Energy within an amplified upper trough moving into the West during the weekend should produce a closed low over the southern Rockies by early Monday, followed by northeastward progression of the upper low and associated strong southern Plains surface low pressure into mid-late week. This system will spread a broad area of significant weather from the Rockies eastward--potentially heavy snow over the central Rockies and vicinity, heavy rain over central/southern latitudes of the eastern half of the country, and severe thunderstorms from Texas through the Deep South. Some precipitation in the northern fringe of the moisture shield could be in the form of snow. Behind this system a strong upper ridge will build into the West, bringing mostly dry and warm weather to the region. A leading system will depart from New England on Sunday. ...Guidance Evaluation/Predictability Assessment... The 00Z/06Z cycle of guidance offers a combination of refinements, ongoing discrepancies, and trends over the forecast domain. Latest solutions are generally becoming better defined with the upper low likely to close off over New Mexico by early Monday and then continue northeastward over the Plains, including holding onto an upper low (or implied low, depending on the contour interval of upper heights) somewhat longer due to slightly later phasing with incoming northern stream energy. Upstream, recent guidance has been very inconsistent with what will happen as Pacific energy encounters the upper ridge building into western North America, affecting some aspects of the central U.S. storm. Multi-day model/ensemble mean trends have generally been toward a stronger ridge. Meanwhile guidance is split over important details of eastern North America flow during Monday-Wednesday. The ECMWF/ECMWF mean and UKMET show stronger east-central Canada upper ridging and better connection with the eastern U.S. ridge, leading to more Northeast troughing versus the GFS/GEFS mean and CMC/CMC mean. This ultimately leads to some significant differences in surface pattern and precipitation coverage over the East. Thus far the more probable solution appears inconclusive from trends, though the amplified nature of the upstream pattern could tilt things a bit toward the ECMWF cluster. The 00Z CMC became questionably suppressed with its surface pattern late in the period. An operational model blend provided a good depiction of consensus for the first half of the period. Then the forecast trended to a blend of the 06Z GFS/GEFS mean and 00Z ECMWF/ECMWF mean as detail uncertainties increased within a fairly agreeable large scale pattern. ...Weather Highlights/Threats... The surface low departing from the Northeast on Sunday will likely produce some lingering rain/snow showers across the region. Otherwise the East will see fairly dry weather into the start of next week. Guidance discrepancies lead to low confidence for what could be a narrow band of precipitation over parts of the Great Lakes/Northeast around Monday. Attention then turns to the central U.S. as a fairly strong surface low develops over the southern Plains by Monday, with leading low level Gulf inflow and a warm front lifting northward helping to focus a threat of heavy rainfall over parts of the southern Plains/Lower Mississippi Valley and eventually farther eastward. There is a strong model signal for heavy rainfall that could result in instances of flash flooding, mainly later in the day Monday and especially into Tuesday and persisting into early Wednesday. There is also a threat of severe thunderstorms from eastern Texas eastward across the southern tier states. Check the latest Storm Prediction Center outlooks for the updated information on the severe threat. Meanwhile parts of the central Rockies and vicinity may see a period of heavy snowfall with significant rainfall possibly extending into the central Plains (but likely somewhat lower totals than expected to the southeast). Precipitation coverage from the northern Plains into Northeast has much lower confidence, but if moisture reaches that far north some precipitation could be in the form of snow. Ahead of the developing Plains storm, above normal temperatures will progress from the Plains into the East. Some readings could be as high as 20-25F above normal over parts of the northern Plains/Midwest on Sunday-Monday. Farther eastward the greatest anomalies should be in the plus 10-20F range with morning lows tending to be warmer relative to normal versus the highs due to the moisture/clouds. System passage will bring an area of below normal temperatures from the West into the Plains, with some areas of highs 10-20F below normal. Coolest highs relative to normal should be over the southern half of the High Plains on Tuesday. The upper ridge building into the West will promote a significant warming trend over the region with expanding coverage of highs 10-20F or so above normal from Tuesday onward. Best potential for temperatures to challenge daily record highs will be over California. Also, a few daily record highs could be possible over the Florida Peninsula around Tuesday-Wednesday. Rausch/Hamrick Hazards: - Heavy snow across portions of the the central Rockies into the central High Plains, Mon-Tue, Mar 21-Mar 22. - Heavy snow across portions of northwestern Wyoming, Sun, Mar 20. - Heavy precipitation across portions of the central High Plains, Mon-Tue, Mar 21-Mar 22. - Heavy rain across portions of the central and southern Plains, Mon-Tue, Mar 21-Mar 22. - Heavy rain across the lower and mid-Mississippi Valley, the Tennessee Valley and the Ohio Valley, and into the western slopes of the central/southern Appalachians, Tue-Wed, Mar 22-Mar 23. - Heavy rain across portions of eastern Gulf Coast into the interior Southeast and Mid-Atlantic, as well as the southern to central Appalachians, Wed-Thu, Mar 23-Mar 24. - Severe weather across much of eastern Texas into the central Gulf states, Mon, Mar 21. - Severe weather across the central Gulf states, Tue, Mar 22. - Severe weather across the eastern Gulf states, Wed, Mar 23. - High winds across portions of the southern Rockies and southern High Plains, Mon, Mar 21. - High winds across portions of the central Rockies and central High Plains, Tue, Mar 22. 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