textproduct: Wilmington

WHAT HAS CHANGED

Adjusted snowfall amounts slightly but no significant changes. Slightly increased the forecast for mixed precipitation in southern Ohio and northeast Kentucky.

Added chance of snow on Wednesday into Thursday.

KEY MESSAGES

1) Cold Weather Advisory in effect into Saturday morning.

2) A significant winter storm beginning Saturday will bring heavy accumulations of snowfall, with impacts to travel expected to continue through Monday.

3) Dangerously cold temperatures, with wind chills below zero Monday and Tuesday mornings, and temperatures expected to remain below freezing through the entire week.

4) Snow possible Wednesday into Thursday.

DISCUSSION

KEY MESSAGE 1) Cold Weather Advisory in effect into Saturday morning.

A very cold air mass has settled into the region, with continued cold advection today. Wind chills below zero are expected tonight, with values near -10F across the majority of the ILN forecast area on Saturday morning.

KEY MESSAGE 2) A significant winter storm beginning Saturday will bring heavy accumulations of snowfall, with impacts to travel expected to continue through Monday.

There are no significant changes to the forecast for the winter storm expected this weekend, which is expected to be a long-duration event of heavy snowfall, with 8-12 inch totals expected for a majority of the forecast area.

Snowfall is initially expected to begin Saturday afternoon, perhaps slightly slower than indicated by previous forecasts. This initial round of snow Saturday afternoon and evening will not be significant, with only an inch or two for most locations before there is somewhat of a lull in snowfall intensity. As surface low pressure moves northeast into the Tennessee and Ohio valleys Sunday, a much more focused area of precipitation will envelop the ILN CWA, producing the majority of the snowfall over the area on Sunday.

One of the main complications is the potential for mixed precipitation, as warm air attempts to move northward into the forecast area. There has not been any kind of significant northward shift in the 12Z models, with some models showing mixed precipitation reaching the ILN CWA, and others keeping it just to the south. Historically, this kind of thing tends to occur and may not be picked up on by all of the models well in advance. Have tried to account for this possibility by including a slight chance of sleet in the forecast as far north as Cincinnati and Chillicothe, but the greater chance for sleet and freezing rain will be in far southern Ohio and northeast Kentucky. Made some slight adjustments to add small amounts of ice, and reduce snow amounts by around an inch, in locations such as Lewis County KY and Scioto County OH. This part of the forecast remains somewhat low in confidence, and additional adjustments should be expected.

For the rest of the area, where precipitation remains all snow, the long duration combined with somewhat-favorable rates and snow ratios will enable this event to produce significant snowfall. There is high confidence that at least some locations in the forecast area will receive 10+ inches of snow, though the exact swath of heaviest amounts is not yet clear. For the far northern ILN CWA (north of Dayton) amounts should be somewhat lighter, but above the 6 inch warning criteria for that area.

Regardless of any potential changes in precipitation type in the southern portions of the forecast area, or slightly lesser snowfall amounts in the northern portions of the forecast area, overall this will be an event that will produce significant impacts -- mainly Sunday into Monday. Even when snow ends, the very cold temperatures will make cleanup difficult, so travel troubles will continue well into the day Monday. The Winter Storm Warning is in effect through noon Monday.

3) Dangerously cold temperatures, with wind chills below zero Monday and Tuesday mornings, and temperatures expected to remain below freezing through the entire week.

Temperatures will be well below normal through the rest of the week, with almost no chance of getting above freezing at any point. Min temps in the single digits, and below zero Tuesday morning, will exacerbate the hazards from this cold. As of now, wind chills appear to be the coldest Tuesday morning, with wind chill values getting as low as -10F to -20F. Still some uncertainty on how strong winds will be Tuesday morning, but that will have an impact on how cold the values get, and there may be some room to drop further -- especially if the models are under-doing the min temps after the snow pack is in place.

4) Snow possible Wednesday into Thursday.

As an upper trough enters the Great Lakes, with very cold air still over the Ohio Valley, snow snow may develop late Wednesday into Thursday. Still a lot of uncertainty at this distance, but some accumulations may be possible.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

VFR will prevail through the period. Will continue to have mid and high clouds stream across the region. A 4-6kft deck will spread into the area after 18Z. Some light snow may develop into the Cincinnati terminals before the end of the period. North winds will veer to east northeast and fall below 10 kt overnight.

OUTLOOK...IFR to LIFR conditions will occur with considerable accumulating snow Saturday night into Sunday evening. MVFR ceilings MVFR ceilings and visibilities possible Tuesday afternoon through Wednesday.

ILN WATCHES/WARNINGS/ADVISORIES

OH...Cold Weather Advisory until noon EST Saturday for OHZ026-034-035- 042>046-051>056-060>065-070>074-077>082-088. Winter Storm Warning from 10 AM Saturday to noon EST Monday for OHZ026-034-035-042>046-051>056-060>065-070>074-077>082-088. KY...Cold Weather Advisory until noon EST Saturday for KYZ089>100. Winter Storm Warning from 10 AM Saturday to noon EST Monday for KYZ089>100. IN...Cold Weather Advisory until noon EST Saturday for INZ050-058-059- 066-073>075-080. Winter Storm Warning from 10 AM Saturday to noon EST Monday for INZ050-058-059-066-073>075-080.