Extended Forecast Discussion NWS Weather Prediction Center College Park MD 257 PM EDT Thu Apr 10 2025 Valid 12Z Sun Apr 13 2025 - 12Z Thu Apr 17 2025 ...Overview... Guidance shows a fairly progressive pattern for the Sunday- Thursday period. An upper low anchoring an amplified East Coast trough as of early Sunday will lift away while the next trough initially over the northern Rockies amplifies into the Plains and then eastern U.S. An upper low within the latter trough should track near the Canadian border and provide the dynamic support for a Plains through Upper Great Lakes and eastern Canada surface low that will push a cold front through the eastern half of the country. The combination of northern stream Pacific energy and what is left of a weakening upper low coming into the Southwest around Tuesday may reach the Plains/Mississippi Valley by next Thursday and reflect at the surface as one or more waves/frontal systems. Confidence in details is on the lower side though. Also at that time another upper low should reach offshore southern California while some ridging builds over the western U.S. into Canada. Most precipitation with the above systems should be light to moderate and confined to locations east of the Rockies, with the relatively higher totals over the far northern tier on Sunday and parts of the central/south-central Plains into Mississippi Valley mid-late week. ...Guidance/Predictability Assessment... There is reasonable clustering in principle for the system departing from the East Coast and the next feature emerging from the Rockies/Plains. Dynamical and machine learning (ML) models and ensembles show rapidly increasing spread for some aspects of larger scale flow across the western half of the country by next Wednesday/Thursday. The departing East Coast system continues to exhibit some detail differences, with the most notable being the GFS leaning to the northern extreme of the spread (more in the 12Z run versus the 06Z version). Farther west, GFS/CMC runs have been gradually trending northward toward the remaining dynamical/ML consensus for a developing upper low to track near the Canadian border. Interestingly the 00Z/06Z GFS actually briefly opened the upper system over the Upper Midwest by Monday while remaining guidance has been advertising a consistent signal for an upper low near the northern Minnesota border. Thereafter, guidance exhibits typical spread for upper/surface low specifics and good agreement for the upper trough reaching the eastern U.S. A majority/consensus approach among the 00Z/06Z operational models looks good for the depiction of these systems. Guidance has been having more difficulty in resolving specifics over the eastern Pacific into western North America, with varying amounts of trough energy splitting while nearing the West Coast. Solutions are clustering toward one upper low coming into the Southwest around Tuesday while weak shortwave energy reaches the Pacific Northwest and western Canada. Then by Wednesday-Thursday latest trends are for the Southwest upper low to open up but with the remaining shortwave maintaining some definition as it crosses the Rockies/Plains while the northern energy begins to amplify downstream from a ridge that builds into and north of the western U.S. There is a minority ensemble cluster and a couple ML models that show significantly more trough amplification over the Interior West or Rockies though, and the 00Z AIFS mean hints at a combination of these ideas. Meanwhile another upper low should reach a position offshore southern California by next Thursday. A trend toward half models and half means (06Z GEFS/00Z ECens) by late in the period provides a reasonable account for latest operational model trends but lower than average confidence in some of the specifics at that time. At the very least, even with the guidance spread there is a decent signal for a general axis of lower surface pressures over the Plains by next Thursday with GEFS/ECens ensembles showing the general idea of an east-central U.S. rain area. ...Weather/Hazards Highlights... Eastern parts of New England should see lingering rainfall on Sunday with the system tracking away from the East Coast. Meanwhile the developing northern Plains into Upper Great Lakes system should bring a band of enhanced rainfall with the possibility of some pockets of snow across parts of North Dakota and Minnesota, with some rain/snow continuing across the Great Lakes/Northeast through the first half of next week. Best potential for some snow accumulation should be over the U.P. of Michigan and to the lee of the eastern Great Lakes and high elevations of the Northeast. There will also be some rainfall along the system's trailing cold front, but likely with light to moderate amounts. Note that the Storm Prediction Center is monitoring the potential for some strong convection over parts of the Ohio Valley on Monday (mostly wind threats). Expect rainfall with the above systems to stay light enough not to present flash flood concerns, so the Days 4-5 EROs depict no risk areas. Flow behind the northern tier storm should produce strong and gusty winds over the northern/central Plains Sunday into Monday, with some brisk winds reaching into the Great Lakes/Northeast thereafter. A weakening upper low reaching the Southwest by Tuesday may produce some very scattered and light precipitation. Depending on the definition and surface reflection of this energy farther eastward, there may be a band of rainfall with varying intensity from parts of the central/south-central Plains eastward through the Mississippi Valley by Wednesday-Thursday. The mid-upper level ridge axis across the Plains on Sunday will support widespread above normal temperatures (plus 10-25F anomalies) from the Desert Southwest to the central and northern Plains. Highs could reach into the 90s from western Texas to eastern Colorado and western Kansas, before the cold front brings readings closer to climatology for Monday. Some daily records are possible on Sunday, especially over the southern High Plains. The warmth will moderate as it continues eastward into Monday and early Tuesday. Then the cold front pushing across the eastern half of the country will bring near to below normal readings, with highs up to 10-15F below normal over parts of the East around midweek. General mean ridging aloft over the West will support an expanding area of above normal temperatures over the West and eventually including the Plains Monday onward, with fairly broad coverage of plus 10-20F anomalies. Rausch/Hamrick 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 forecast (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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 https://www.wpc.ncep.noaa.gov/#page=ovw