If you are having a New Year's Eve party to ring in the new year, make some sleep-over plans. It's best not to drive after midnight. And please don't drink and drive in the icy weather. That is a terrible idea.
.SYNOPSIS... Issued at 345 AM EST Thu Dec 31 2020 Surface high pressure will lift northeast across central Indiana today and provide a brief respite in the late year precipitation. Things will change in a big way overnight tonight though as a strong storm system lifts northeast out of Mexico. This system is expected to result in several hours of freezing rain early New Year`s Day before strong southerly flow warms things way up which will result in a transition to moderate to locally heavy rain New Year`s day. Aside from a small chance of rain and snow Saturday night associated with another system, high pressure will result in dry weather with slightly above normal temperatures through the middle of next week. && .NEAR TERM /Today/... Issued at 345 AM EST Thu Dec 31 2020 Today will see a break in the precipitation as surface high pressure lifts northeast over central Indiana. However, dew points in the lower 20s will help set the stage for icing tonight into New Year`s Day. Dry punch should allow breaks in the clouds late morning and afternoon. However, northeast and east winds will not allow the temperature to recover too much with near normal highs in the middle and upper 30s. && .SHORT TERM /Tonight through Saturday night/... Issued at 345 AM EST Thu Dec 31 2020 The year 2020 like it does not want to go down easy as it wants to curse the start of 2021 with a glaze of ice as a strong upper Mexican system will lift northeast into eastern Texas this evening and into eastern Oklahoma overnight and into the Ozarks on New Year`s Day before shearing out over the Great Lakes Saturday early. Meanwhile, surface reflection lifts northeast across central Indiana 21z New Year`s Day to 03z Saturday. Strong isentropic lift returns once again after 03z tonight from southwest to northeast. BUFKIT soundings showing a classic freezing rain sounding for several hours after the atmosphere saturates again from top to bottom overnight into New Year`s Day morning. East and northeast winds around the retreating surface high will keep the near surface below freezing. The exception will be far southwestern counties, where the temperatures may remain near, at or slightly above freezing. Meanwhile, strong warm advection, deep moisture, increasing low level jet and coupled 120 knot plus northern Great Lakes and Lower Mississippi Valley jet streaks, will supply strong forcing and the moisture needed to moderate precipitation overnight and into New Year`s day. 30 millibar or less condensation pressure deficits on the 300K surface, suggesting a saturated column, will move from southwest to northeast across the forecast area. This all suggests rain, possibly freezing, will move into Knox county around 06z. As the precipitation shield heads further northeast, most or all of the precipitation will be freezing rain with a possible brief mix with sleet or snow at the onset from evaporative cooling in lowest levels prior to complete saturation of the column. This precip shield should reach the metro area after 09z and far northern counties around 12z. Soundings and surface temperatures suggest most areas will see around 4 hours of freezing rain, which will be moderate much of the time, perhaps even locally heavy. This is an slightly gusty winds, support ice accumulation amounts from around 0.05 inches in southwestern sections to around 0.20 inches across northern sections. After coordinating with local offices, decided to go with a Winter Weather Advisory for freezing rain from 08z-16z New Year`s Day from Vermillion county southwest to Decatur county and north. The temperature will then warm above freezing from around 12z-16z from southwest to northeast, so will likely be able to clear counties on an hourly or so basis from southwest to northeast. After that, the main focus will be rain. Models suggest a widespread inch is possible before things wind down from southwest to northeast as the systems shears into the Great Lakes. The strong forcing mentioned early and low level jet increasing to 50 knots during the afternoon, certainly supports locally heavy rain and possibly minor low lying flooding. It now looks like dry weather Saturday will be brief as the next southern system lifts northeast across the area and becomes negatively sheared as it does so. Deepening moisture and sounding profile support a shot of rain and snow Saturday night with minor snow accumulation possible.
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