textproduct: Wilmington

WHAT HAS CHANGED

Winter weather advisory issued for snowfall this evening.

KEY MESSAGES

1) Snow will develop late this evening and continue into the overnight hours for areas along and east of Interstate 71. Snow, along with cooling pavement temperatures, are likely to cause slippery roads.

2) Snow showers continue throughout the day on Saturday. Some snow showers will result in sudden drops in visibility, along with a quick coating of snow.

3) Bitterly cold temperatures are forecast Saturday night through Wednesday morning with the coldest temperatures occurring Monday through Tuesday morning.

DISCUSSION

KEY MESSAGE 1... Guidance this morning has trended colder and wetter as low pressure over the Great Lakes pushes a cold frontal boundary through the middle Ohio Valley tonight. A disturbance along the front will bring a surge in moisture and precipitation into our southern and eastern zones starting late this evening. The challenge with this forecast is precipitation type. Aloft, the column will be below freezing, with near to slightly above freezing temperatures limited to the lowest thousand feet or so. Despite this marginal thermal environment, we expect dynamic cooling will play a role in shifting us toward a snowier solution. The most uncertain part of the forecast is the western edge of the precipitation shield. Have issued an advisory for higher confidence areas, with a later westward expansion as a possibility as we focus in on spatial coverage of the snow. Amounts will range from one to three inches where the highest QPF resides in the southeast... with lesser amounts along the back edge along the I-71 corridor.

KEY MESSAGE 2...

Although widespread snow will have ended by early Saturday morning, a stronger, secondary cold front and the associated cooler air is still moving through Illinois and Indiana. Southwesterly flow assists surface warming during the late morning and early afternoon ahead of the cold front, however, colder air moving in aloft steepens lapse rates, supporting the potential for snow showers from the late morning and into the afternoon across the area. Widespread accumulations are not expected with this activity but locally, reduced visibility and quick coatings of snow may result in challenging travel conditions. The cold front arrives in the late afternoon and early evening, with additional snow showers and minor accumulations forecast.

KEY MESSAGE 3...

Confidence remains high in a lengthy period of bitterly cold temperatures stretching from Sunday through Tuesday night.

The initial surge of colder air arrives late Saturday night into Sunday morning with a leading shortwave moving through the base of a deep trough over the eastern CONUS. Temperatures in the teens Sunday morning, combined with 10 to 15 mph winds, produce wind chill values in the single digits to zero across the area. A secondary, reinforcing surge of bitterly cold air arrives behind another shortwave Sunday night into Monday morning. Due to the air mass arriving during the day on Monday, temperatures will struggle to climb even a couple of degrees during the day. Wind chill values are near zero to below zero area wide with the coldest wind chills between -10 and -15 Monday evening. The lack of warming throughout the day on Monday sets the stage for the coldest period Monday night and Tuesday morning. Wind chills below zero are forecast area wide with much of the area seeing anywhere from -10 to -20. For NWS ILN headline criteria, visit www.weather.gov/iln/criteria-winter.

It is important to note that while the coldest values may arrive Tuesday morning, the winds are strongest Monday afternoon and evening with 25 to 35 mph wind gusts. Temperatures rebound briefly on Wednesday ahead of an approaching cold front before another cold front brings cooler temperatures for Thursday and Friday.

Now is the time to plan for an extended period of extreme cold by inspecting your residence, vehicle, and have plans in place for outdoor livestock. For information on how to prepare yourself, your home, and your car for extreme cold, visit www.weather.gov/safety/cold-before.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

VFR conditions initially will deteriorate later this evening as a frontal system shifts east across the terminals and brings deeper moisture and the potential for snowfall. Most significant impacts will be from Cincinnati through ILN and potentially as far north as CMH/LCK. Have relatively high confidence in IFR conditions after 00Z, with IFR visibility less certain further north where snowfall rates will be lower.

As this system exits to the east, a stronger cold front along with very cold air aloft will dig southeast into our area during the day on Saturday. Snow showers will develop as lapse rates steepen. Coverage should be relatively sparse but any transient shower is likely produce quick reductions in visibility below IFR thresholds.

OUTLOOK...Winds may gust to 30 kts Monday.

ILN WATCHES/WARNINGS/ADVISORIES

OH...Winter Weather Advisory from 7 PM this evening to 7 AM EST Saturday for OHZ064-065-073-074-079>082-088. KY...Winter Weather Advisory from 7 PM this evening to 7 AM EST Saturday for KYZ094>100. IN...None.