Update On Wintry Precip Potential Tonight & Cold Blast This WeekMarch 17th, 2013 at 9:33 pm by Chad Evans under Chad's WLFI Weather Blog
LEADING EDGE OF LARGELY RAINFALL (RIGHT NOW) QUICKLY APPROACHING…………..
Leading edge of precipitation is now approaching I-70 in central Indiana & moving northward. Most of it is rain. Meanwhile, dry, cold east flow is bleeding in the winter dry chill into our viewing area. East winds are gusting to 27 mph in places.
SKEW-T POINTS TO EVAPORATIVE COOLING, THEN OVERRUNING PRECIP……….
Looking at our Skew-T & projected Skew-T’s, I would not be surprised to actually see this precipitation begin as all snow for a bit, but then quickly transition to sleet & freezing rain, then all freezing rain. This applies to the entire viewing area, but the better potential of minor accumulations of ice would be northeast of a Rensselaer to Lafayette to Frankfort to Tipton line & northeastward. Snow or sleet accumulation would be limited to brief, very light dusting, with perhaps brief less than 0.5″ accumulations in our northeastern counties.
Low temperatures tonight will drop to 28-32 at the surface.
PRECIPITATION PROCESSES………ISOLATED THUNDER CLAP/LIGHTNING FLASH…………
I say all of this because I feel that as precipitation falls through very dry, cool mid-level & low-level air, snow may make it totally to the ground at the onset, as there will be evaporative cooling at first. However, with time, as slow migration of warmer air tries to overtake the cool dry air, thinking flakes will melt to a raindrop, then re-freeze into an ice pellet (sleet), then with quick expansion of that warm layer from the south, a trend to freezing rain will develop. Also, as this warm air overrides the cold air at the ground & wedges itself between cool air aloft, there will be bits of elevated CAPE (instability). So, isolated lightning flash/thunder clap is not out of the question.
Seems like we have had several instances of lightning/thunder with snow, sleet, freezing rain or rain this winter/spring. Friday evening, I had thunder reports in Boone & Tipton counties with Alberta Clipper. Clipper produced t’shower with hail nearly to penny size in Hamilton County, Indiana that evening!
Freezing rain will change to all rain Monday morning. The majority of the more organized, widespread rain will exit in the morning, but some patchy light rain & drizzle may linger in places into the afternoon.
UNSEASONABLY COLD AIRMASS…………….HIGH TEMPERATURES 20 DEGREES BELOW NORMAL BY MID-WEEK……….
Meanwhile, an UNSEASONABLY COLD airmass will move into Minnesota & Iowa tonight-tomorrow, accompanied by heavy snow & strong winds (BLIZZARD WARNING), while a MAJOR WINTER STORM will blast the Northeast U.S. Parts of North Dakota & Minnesota will drop to -15 & Iowa may see temperatures near 0. Both point towards a chunk of unseasonably cold air blasting into our area tomorrow night-Tuesday.
It is looking more & more like a chunk of the viewing area may not even reach 30 mid-week with overnight lows in the middle to upper teens. There may be multiple nights in the teens.
In terms of the Friday &/or Saturday systems, some models have it staying south & southwest of here, others bring it in. I like chance or rain &/or snow for Friday &/or Saturday still. It will begin to warm up after Saturday. Highs next Monday may even reach 45-50 degrees.