textproduct: Wilmington

SYNOPSIS

A system moving across the region will quickly move off to the east tonight. Arctic air will settle into the region behind the snow, bringing bitterly cold temperatures into Monday. This will be followed by a substantial warm up through midweek.

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/

Update...

Two bands of enhanced snow have set up across our area late this afternoon. The first one is along and just north of the I-70 corridor and the second one is just along and north of the Ohio River. Colder air is moving in from the north and this will continue to increase SLRs through early evening from north to south. The last few runs of the HRRR have picked up on these two bands and our indicating that the highest snow amounts will likely end up being with the second/southern band. Have therefore nudged up totals across parts of our southern areas where 5 to 7 inches storm total snow amounts seem possible from Hamilton/Butler Counties eastward through through Highland, Ross and Pike Counties (also including northern portions of Clermont, Brown, Adams and Scioto Counties). There is a back edge of the heavier pcpn moving east across southern Indiana attm so would expect the heavier snow to taper off fairly quickly from west to east later this evening.

Previous discussion...

Initial area of mid level frontogenesis has caused snow to quickly spread across the area. This initial burst will move off this afternoon but be rapidly followed by another enhancement of snowfall rates late this afternoon into this evening as another concentrated area of frontogenesis moves through ahead of the mid level short wave. The early activity will continue to be aligned more west to east while the latter will pivot to more of a southwest to northeast orientation. The entire system will be quick to depart through the evening with precipitation ending in far southeast counties by 06Z.

Despite being a quick hitter, substantial snowfall will occur. Snow to liquid ratios become greater with time as cold air start to spill into the region in the wake of a front crossing the area this afternoon. SLRs during the time of heaviest precipitation will generally range from 15:1 to 20:1. Trends in high resolution guidance have led to a tighter gradient in precipitation on the southern edge of this system which will limit snowfall amounts across much of northern Kentucky. However, north of there, QPF has gotten slightly higher. The corresponding increase in snowfall from higher forecast precipitation has led to expansion of the winter storm warning into the I-70 corridor. With banding, there may be localized amounts of 8 inches or more, especially wherever that pivot point ends up being.

Arctic air will continue to spill into the region through the overnight hours. Winds are forecast to stay around 10 to 15 mph. The combination results in bitter wind chill. Cold advisory has these conditions covered well.

SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/

Arctic high will build southeast with the center of the high moving into central Kentucky by late Sunday night. This will result in winds decreasing but perhaps not completely decoupling Sunday night. Record cold highs will be in jeopardy on Sunday, although highs for the day may end up being at midnight. After initially decreasing late tonight into Sunday morning, clouds are expected to have some diurnally driven increase which should then diminish Sunday night.

Record cold maxima for December 14: CVG 15 in 1917 CMH 16 in 1917 DAY 16 in 1917

Apparent temperatures will rise above the cold weather advisory criteria Sunday afternoon. They will fall again Sunday night even with lighter winds because of colder air temperatures. It may be marginal whether some of the area reaches the criteria, but no changes were made to the timing of the advisory at this stage.

LONG TERM /MONDAY THROUGH SATURDAY/

Mid level flow will become zonal early in the period with broad consensus in bringing a short wave across the region Thursday into Thursday night. Within this consensus there is still a decent amount of spread, primarily in amplitude and lesser so in the timing. Looking at the cluster analysis, these differences are not making a substantial difference in sensible weather, at least for that far out in time when we are not too concerned with details. This short wave will bring a cold front across the region Thursday afternoon and evening with showers ahead of it. The strength of the system will largely influence the QPF as well as how strong the wind fields are both pre and post frontal. That will be resolved as this gets closer in time, but for now a broad brush suffices.

Other than this system, the main feature of this period will be the big warmup that will take place after the brief Arctic intrusion. Temperatures are still going to be around 20 degrees below normal on Monday, but then readings will be jumping 7 to 10 degrees each following day into Thursday. It will take until Wednesday to even approach normal with ensemble probabilities still rather low to reach this threshold (20 to 30 percent). Thursday will definitely rise above normal, although to what degree is not entirely clear. Probability of reaching at least 50 range from 80 percent across northern Kentucky to near 30 percent north of I-70.

In the immediate wake of the front, temperatures will fall back below normal on Friday but with dry conditions as high pressure moves through. This cool down will be brief with temperatures pushing 50 again by Saturday (probability 30 to 70 percent). The warmth will come with a chance of rain, although there is quite a bit of spread on that potential. GFS ensemble is the most robust with precipitation chances with almost all of its members generating precipitation. About half of the Canadian ensemble members follow suit. But the other half of the Canadian along with most of the ECMWF members are more scant.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Widespread moderate to locally heavy snow and IFR conditions will continue for the first couple of hours of the TAF period. The snow will begin to taper off from the west through late evening. MVFR clouds will then linger into the early morning hours before beginning to scatter out late tonight. MVFR stratocu will redevelop through late morning and continue through the afternoon.

OUTLOOK...MVFR to IFR conditions possible Thursday.

ILN WATCHES/WARNINGS/ADVISORIES

OH...Winter Storm Warning until 7 AM EST Sunday for OHZ053>056-060>065- 070>074-077>082-088. Cold Weather Advisory until 11 AM EST Monday for OHZ026-034-035- 042>046-051>056-060>065-070>074-077>082-088. Winter Weather Advisory until 7 AM EST Sunday for OHZ026-034-035- 042>046-051-052. KY...Winter Storm Warning until 7 AM EST Sunday for KYZ091>093. Cold Weather Advisory until 11 AM EST Monday for KYZ089>100. Winter Weather Advisory until 7 AM EST Sunday for KYZ089-090- 094>100. IN...Winter Storm Warning until 7 AM EST Sunday for INZ050-058-059-066- 073>075. Cold Weather Advisory until 11 AM EST Monday for INZ050-058-059-066- 073>075-080. Winter Weather Advisory until 7 AM EST Sunday for INZ080.