Thunderstorm Potential Tonight.

After looking through the model data, it looks the threat for thunderstorms have increased for us, so much that I believe that the SPC will extend the Slight risk area for severe weather as far north as Fort Wayne.  Right now, the Storm Prediction Center has a slight risk area all the way to just south of Fort Wayne, but still keeping us in the thunderstorm risk area.  If not for a strong low level inversion, we would have a much higher threat for severe weather, and even tornadoes.  This low level inversion is occuring to due to two things.  One, the entire still has a pretty decent snowpack, causing cold air to accumulate near the ground, and temperatures close to freezing.  Another factor is a strong low level jet which is transporting warm, moist air northward over top the cold surface air mass, which may for awhile produce freezing rain at the surface.  Through the late afternoon and evening, the surface low pressure system will rapidly strengthen into an incredibly strong low pressure system, which at the same time will cause an intensification of the low level jet, which will bring even warmer and moist air to the region.  This will likely lead to the development of dense fog in the early evening hours, just before winds begin to strengthen.  As soon as the wind strengthens, the low level inversion will rapidly weaken, allowing warm air aloft to mix towards the surface, causing temperatures to rise throughout the night, from 34 in the late afternoon to almost 50 by early tomorrow morning, along with the potential for widespread showers and thunderstorms by the late night hours.  Even though there will not be a whole lot of instability in the lowest kilometer of the atmosphere, forecast soundings indicate that a substantial amount of instability will exist above the 850 millibar layer, which would allow for the development of elevated thunderstorms, which do not form from the surface but begin at the top of the boundary layer (the layer in which friction is a huge factor and in which vegetation and surface heating effect moisture and temperature).  These storms will develop at the leading edge of the cold front.  I have several reasons why many locations around COULD see severe weather tonight.  One reason is because of the elevated instability that I was talking about, which will allow for the rapid development of thunderstorms as the cold front moves through.  Another factor in my forecast are strong mid level winds of over 100 mph, which will drive a strong QLCS (quasi-linear convective system- a squall line that is nearly linear in shape but can still contain damaging winds, hail, and tornadoes.  They usually move through faster than typical squall lines, reducing the threat for heavy rain somewhat.).  These strong winds could potentially mix to the surface if the inversion is weaker than what is forecast.  Severe weather would be more likely if the warm front moves farther north than what is anticipated but the limiting factor here is our fresh snow cover and frigid ground, which is causing a low level cold wedge to remain strong.  Another factor is the the Low Level Jet Stream, which is originating from the Gulf of Mexico, transporting warm, moist air northward into our area.  This will bring plenty of moisture for the development of heavy thunderstorms and will enhance the development of the squall line.  The LLJ will not only enhance the development of thunderstorms, but also very strong non-thunderstorm winds, especially later in the morning Monday as the lapse rates steepen due to cold air aloft and relatively warm surface air.  Snow and rain will pivot around the trough axis through Monday evening before tapering off after the storm system leaves the area.  If all of the above factors are in place, I expect a heavy rain threat, a slight severe weather threat, and high winds to be in place.  If the NAM and RUC forecasts are correct, we may be seeing scattered showers and thunderstorms into the area by 8 or 9 p.m. tonight.  Overnight, farther west, a powerful line of severe thunderstorms will develop and move northeast right into the area.  Down south, in western Tennessee, Mississippi, Arkansas, and Southern Missouri, conditions will be just right for a widespread outbreak of severe weather, including strong, long tracking tornadoes, much like several of last year's deadly tornado outbreaks.  Back home, the squall line will race to the northeast, with damaging winds and hail possible, with heavy rainfall of up to an inch is possible in some areas.  The damaging winds are questionable, as low level inversions tend to damper the effects of damaging winds.  But I can remember a time last year when we had a substantial inversion and a severe weather event occurred, while damaging winds were widespread across the area.  So it is still a possibility that damaging winds could be widespread with thunderstorms tomorrow morning.  Hail is also a possibility but not likely at this time.  Up to an inch of rain is possible with the squall line, but most areas will likely pick up in between a half and a three quarters of an inch.   This will likely lead to flooding problems due to snow melt and an already saturated ground.  As mentioned before, scattered thunderstorms are also possible before this main squall line moves through with fog likely before the line moves through also.  This squall line will likely arrive in the early morning hours tomorrow morning in the time frame of 3- 6 a.m.