A developing coastal storm approaches the Northeast/Mid-Atlantic region later today, with the possibility of a stall off the coast of Maine as well as a rapid plunge of cold air into the system bringing potential for a major snowstorm for the inland regions, particularly the Adirondacks and the Green Mountains, where there is potential of over 18" of heavy wet snow, as well as intense snow rates due to deformational dynamics. In the valleys, totals are expected to be much less, as high boundary layer temperatures will mean most precipitation will fall as rain until the colder airmass arrives. Models have also been suggesting a significant back-end upsloping event is possible, which would hamper cleanup efforts. High QPF numbers combined with an existing snowpack in these regions will lead to flooding concerns in the valleys. To the south, a significant coastal flooding event is forecast due a multitude of factors, including: astronomical high tides due a full moon, easterly winds piling up water along the coastlines, and the rapid intensification of the surface low. Across the entire region, at least 1" of QPF is expected, with the potential for 2" in select locations.
WXD Alert: Active Discussion, Tracking, Observations
Lake effect snow is common across the Great Lakes region during the late fall and winter. Lake Effect snow occurs when cold air, often originating from Canada, moves across the open waters of the Great Lakes. As the cold air passes over the unfrozen and relatively warm waters of the Great Lakes, warmth and moisture are transferred into the lowest portion of the atmosphere. The air rises, clouds form and grow into narrow band that produces 2 to 3 inches of snow per hour or more.
Convective development begins in the evening hours of Friday as the first thunderstorms of the year for most of the region. At the moment, the areas most likely to see a thunderstorm are along the I-95 corridor through North Carolina, Virginia, Maryland, Delaware, and New Jersey. The northward extent of the convective development has been tricky to forecast, but the latest HRRR, the 12z NAM, and the 12z HRDPS have suggested that the NYC metro area, Long Island, and the Connecticut coastline will be enveloped by heavy rain
...Widely scattered strong to severe thunderstorms may occur from parts of central/east Texas to the lower/mid Mississippi Valley on Wednesday. At the surface, a deep surface low will develop east/northeast from eastern CO to eastern NE during the period. A cold front will trek east/southeast across the central and southern Plains during the afternoon into overnight hours. Ahead of this feature, convection will likely be ongoing along a dryline/pacific cold front from south-central OK into central TX. Given these combination of factors, the possibility exists for a few mini supercells. The tornado risk will be conditional on the degree of destabilization. Strong wind profiles with effective shear (60+ kt), will conditionally support a damaging wind threat with the more organized segments of the larger-scale convective band expected to move east from OK/TX towards the MS Valley.The strong to severe threat will likely cease coincident with the nocturnal cooling during the evening.
An Enhanced Risk of Severe Thunderstorms is Forecast Today and/or Tonight. Severe thunderstorms are expected this afternoon into this evening from Arkansas/northern Louisiana to the lower Ohio and Tennessee Valleys. A couple of strong tornadoes will be the main threat late this afternoon/evening from northern Mississippi into parts of western/middle Tennessee, along with damaging winds and isolated large hail.
WX Alert: Hazardous Weather OutlookWXD Alert: Post Discussion
. Total snow accumulations of up to two inches and ice accumulations of a light glaze expected due to freezing drizzle. Ice will be more likely late tonight into early Friday morning. In parts of southern Ohio including Wilmington and Cincinnati total snow accumulations of 1 to 2 inches can be expected. Locally higher amounts of 3 or 4 inches are possible in the worst hit areas. Winter Weather Advisories are in effect for the southern regions with snow showers or flurries expected along the periphery.
...Heavy snow for the Sierra... ...Heavy rain possible for Coastal California will lead to excessive rainfall over parts of Southern California.. A deep upper-level low over the Pacific will move onshore over California on Wednesday then moves farther inland to the Northern/Central Plains by Thursday. Moisture associated with the system will stream into California and begin to wane overnight Wednesday. The moisture and energy will aid in producing rain, heavy at times, over parts of California and snow, heavy at times, over the higher elevations of California through Thursdays morning while beginning to wane.
Several tornadoes hit the Southeast Sunday afternoon, killing at least 22 people in one Alabama county on the USA's deadliest day for tornadoes in almost 6 years. As of late Sunday, there were 26 reports of tornadoes in the South, according to preliminary data from the Storm Prediction Center. Damaging tornadoes also hit Georgia on Sunday afternoon.. Powerful winds or a tornado destroyed several mobile homes in rural Talbotton 80 miles from Atlanta, said Ann Erenheim, director of the Talbot County Emergency Management Agency.
This is a quick storm, with precipitation occurring in a 12 hour timeframe, but it could have significant impacts on Monday. Once again, the uncertainty in track and location of any banding activity is leading to an unusually "unstable" forecast with "nowcasting" changes almost certain. Winds do not appear to be significant at the moment, with the wind threat being maximized the further east a location is. Behind the system, a Canadian high pressure system brings an Arctic airmass to settle in through the middle of the week, so any snow on the ground will be sticking around for quite a while.