Weather Prediction Center (WPC, 300 AM EST Thu Nov 12): a low-pressure system crossing the East is forecast to grow into a large storm as its center passes east of Cape Cod tonight. Steady rain spreads over southern New England by this evening, possibly heavy at times near the coast, with stronger northeast winds and possible minor coastal flooding at high tide along parts of the coast near New York City. Rain is likely to change to snow tonight into Friday over the higher ground of New York, northeastern Pennsylvania and northern New England, with accumulating snow and slick travel likely at elevation; wet snow could fall in the central and southern Appalachians Friday night into Saturday morning. Behind the storm, polar air spreads over much of the central and eastern US: highs well below normal by Friday, lows in the 20s across much of the central US, and below-freezing temperatures as far south as the Deep South by Saturday morning, setting up a widespread frost and freeze across the South and Southeast this weekend. Lake-effect rain and snow continues through Friday, with significant snow possible over higher ground in Michigan's Upper Peninsula. Gusty winds and very dry air raise fire danger in parts of the Southeast today. West: warm and dry through Thursday, with a few daily record highs possible in the Northwest and Great Basin; on Friday a strong Pacific storm brings moderate to heavy rain and strong winds to northern California and the Pacific Northwest, and WPC says heavy snow and strong winds will likely create blizzard conditions in the higher Sierra Nevada Friday night into Saturday morning, making travel dangerous to impossible. A separate system brings showers to southern California Friday and to southern Arizona, New Mexico and western Texas by Saturday morning. Storm Prediction Center (SPC Day 1, issued 11:21 PM CST Nov 11): a Marginal Risk (level 1 of 5) of severe thunderstorms this afternoon over parts of southeastern Pennsylvania, much of Delaware, eastern Maryland and southern to central New Jersey; one or two storms could rotate with some tornado risk, plus small to marginally severe hail and locally strong gusts, weakening by evening. NWS alerts feed (severe and extreme, early Nov 12): Winter Storm Warnings (upgraded from Watches) for the Greater Lake Tahoe area, Mono County, the Sierra Nevada above 5,000 feet including Interstate 80 and Lassen Volcanic National Park, from Friday morning to Saturday morning, and for the eastern Sierra slopes of Inyo County into Saturday afternoon; a Winter Storm Watch for Yosemite, Kings Canyon and Sequoia areas from Friday afternoon to Nov 17; High Wind Warnings for the south-central Oregon coast and Curry County coast and central Siskiyou County tonight into Friday; a High Wind Watch for Surprise Valley, Calif., and northern Washoe County, Nev., Friday; Flood Warnings continue for Mason County, Wash.; Seminole, Brevard, Lake, Volusia and DeSoto counties, Fla.; and Maricopa and Yuma counties, Ariz. (through Nov 17); plus Alaska blizzard, freezing-spray and marine storm warnings. No Tornado Warnings in the feed. Tropics (National Hurricane Center, 1 AM EST Nov 12): no Atlantic formation expected in 7 days; NHC is issuing advisories on Tropical Storm Pena, well southwest of Honolulu, and no other formation is expected in the eastern or central Pacific. Space weather (NOAA SWPC, 08:46 UTC Nov 12): SWPC rates three things on 1-to-5 scales: G for geomagnetic storms (which can stress power grids), R for radio blackouts from solar flares (which disrupt high-frequency radio), and S for solar radiation storms (a concern mainly for satellites and polar flights). All three are at 0 now. An R1 (minor) radio blackout was observed Nov 11, the largest at 21:21 UTC. G is forecast to stay at 0 through Nov 14 (highest expected Kp 1.67, below storm level; no storms expected). Chance of R1-R2 blackouts is 45% and R3 or greater 5% per day through Nov 14 (down from 60% and 15% yesterday), from sunspot Region 4566; S1 chance 5% (down from 15%). SWPC's high-energy electron flux alert continues (a satellite-charging concern, not a grid concern; peak 7,897 pfu Nov 11). No G3 or higher and no SWPC grid warning.