Mistakes. They happen.
.SHORT TERM /Saturday through Sunday night/... Issued at 358 AM EST Fri Jan 29 2021 A strong upper low pressure system will swing out of the plains and northeastward toward Missouri and then Illinois on Saturday/Saturday night. Initially this system moves quickly and the trough is negatively tilted, but as it arrives in the mid Mississippi valley it slows down, straightens up and flattens out, and from there on its motion is very slow across the Ohio valley. The surface low spends Saturday night to Sunday night tracking from western Illinois across southern central Indiana to Ohio. Strong isentropic lift will develop on Saturday afternoon ahead of the low, and a low level jet will provide ample lift and moisture transfer ahead of the low. Still some uncertainty regarding how far north the warm air gets Saturday night on the nose of the low level jet, and this will have a large impact on which areas get rain or a rain snow mix versus snow. That said, models have come into good agreement on the track of the low, if not great agreement on the thermal profiles. Very strong lift will be in place Saturday evening/Saturday night with the aforementioned isentropic lift along with good q vector divergence aloft. With the track of the 700 mb low right across central parts of the area as well, looks like the band of heavy snow could include northern/northeastern counties. With this in mind and potential for 6 plus inches of snow over the northern/northeastern counties, issued a Winter Storm Watch for that area. Also of note, snow should be of the heavy and wet variety, and there is some potential for 30 mph wind gusts to come along with it. Central and southern parts of the area are more likely to get into that warm nose and see enough warming that changeover to a mix and then rain could be pretty quick Saturday night, and thus left the rest of the area out of the watch. Sunday during the day, the surface low tracks slowly enough that warming will be in place for most of the day and expect precipitation to be mainly rain, with the possible exception of the northernmost counties. By late Sunday afternoon, though, the low should be over Indiana or moving just east, allowing some of that cold air to move back in behind it. This should bring a change back over to snow. Since the system is moving so slowly, there is still plenty of forcing from the upper system over us. Thus keep chances for snow going through Sunday night, with wraparound potential lasting into Monday morning. While there is some chance for accumulating snow to ramp back up a little Sunday evening, the event will likely be diminishing at that point as forcing weakens and moisture is cut off. Could wind up seeing total precipitation amounts over an inch across the area given the setup and moisture. With things being relatively dry though and streams running well below normal, should be able to handle this moisture without widespread flooding issues. && .LONG TERM /Monday through Thursday/... Issued at 350 AM EST Fri Jan 29 2021 While the progressive mid-level pattern for the period will perhaps exhibit more amplification than earlier this winter, when some of the southern-stream systems` circulations wholly cut-off from the northern jet...true arctic air will still be very much absent from the northwest flow entering Indiana Monday morning. Nevertheless, following any last snow showers that should taper off during the day Monday...the approaching surface high will bring near to slightly- below normal temps to start the work week. Residual considerable cloudiness will likely linger Monday from the departing winter storm`s last lobe of troughiness. Upper level ridging will then join the surface ridge`s building-in amid the mid-level`s greater amplification...providing a decently pleasant-for-mid-winter Tuesday-Wednesday, featuring lighter winds and partly to mostly clear skies. Moderation should follow around the Wednesday time frame courtesy southeasterly flow as the surface high drifts to the east. Attention will soon thereafter turn to the next mid-latitude storm that will be coming out of the Rockies. Some disagreement exists on how fast this next system deepens at the surface, although there is at least moderate confidence its central pressure drops significantly by late Wednesday over the central High Plains, before tracking a good ways to our region`s west on Thursday. Guidance is indicating this system`s wave may actually tap into at least a piece of arctic air by late week, although this detail will be hammered out in the days to come. For central Indiana, progged to be on the system`s generally warm side, southerly breezes should provide an ample ribbon of Gulf moisture. The storm`s cold front will focus at least chances of rain, or mix-to-rain Thursday. Temperatures for the period through Wednesday are expected to range from morning lows in the ~20F realm, while afternoon highs slowly moderate through the 30s for most locations. Wednesday night- Thursday is expected to feature readings well above normal.
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