Another Forecast Update

Since I didn't really address the rain issue in the first post, I will address it now.  According to current radar and surface observations, convective bands of localized have developed and are moving north and eastward at slow rates.  These convective bands are a result of weak mid level instability, and a unique phenomena called slantwise convection.  Intstead of regular convection, which results from upward growth of large cumulus clouds, slantwise convection develops when air moves diagonally instead of directly upward.  Since this upward motion is not intense, lightning and thunder are rare with these bands of rain, but because of the how moist the atmosphere is, and how large scale this upward motion is, heavy rainfall can result from these bands of rain.  I believe this is exactly what is occurring right now, over most of our area.  Therefore, I believe that many areas will receive periods of rain for several hours, before changing over to snow (mainly north of Route 6).  South of Route 6, rain will not change over to snow until boundary layer temperatures cool just enough so that the warm layer is not as deep, which will result from intense synoptic scale lifting and cooling of dry air at the 850 millibar level, mixing with the warmer temperatures of the boundary layer, and causing a much more unstable situation.  This could also initiate even more bands of locally heavy rain.  For this reason rainfall totals will be anywhere in the range of a quarter to a half inch or possibly more.  By early tomorrow morning, most if not all precipitation will be snow in the area with around an inch of snow possible south of Route 6, and several inches north of Route 6.  Other than that, that is the only thing that has changed since my last blog post.

Important Forecast Update

I am very sorry for not posting since Tuesday, but I have been very busy.  As for this post, I need to update the forecast, as some very drastic changes have occurred.  One important thing is that the relatively weak storm system forecast a couple of days ago, has instead become a very strong low pressure system center over Missouri, with a central pressure of at least 990 millibars.  This system has formed in response to a rapidly strengthening jet streak currently situated over the area.  Because of the jet streak, intense lifting is occuring over a widespread area, but with the little moisture that is present, only a narrow band of precipitation has set up over the Midwest, with some areas located within the more intense lifting region experiencing rain changing over to snow.  Right now, the main band of precipitation over our area is mainly rain with some mixing of snow over lower Michigan.  This initial band of precipitation will shift out of the area, with maybe even some partial clearing south of Route 30, but other than that thick clouds will persist over the area.  Intense ascent and lifting due to the temperature gradient south of the area will cause bands of rain to redevelop in most of the area, with areas north and west of Route 6 experiencing rain mixing with snow, or completely changing to snow especially across southern Michigan.  My current thinking is that the jet streak will back build and intensify, causing more intense lifting, and eventually causing most if not all of our precipitation to change to snow after 2 a.m.  The only reason why rain instead of snow is falling currently is because of temperatures near the surface are several degrees above freezing.  Other than that, as soon as we can get temperatures in lowest three thousand feet to cool at least close to freezing, snow will begin to fall.  In some areas, this will occur faster, especially in lower Michigan, far Northern Ohio, and Indiana.  For areas south of Route 6, this changeover will not happen until after late night hours, possibly as late as midnight, especially south of Route 30.  The area that has the most uncertainty right now is the U.S. 24 corridor, as models have not shown any consistency, and have not made it clear where this storm system will move to.  My current thinking is that this system is going to move just south of the area, putting us in the zone of the most intense lifting and warm air advection, which will delay the transition from rain to snow over areas south of U.S. 6.  If the storm does happen to move farther south than indicated, rain will change to snow much more quickly, and bring much higher accumulations to the area.  In the region of Northwest Ohio and Northeast Indiana, the highest snowfall totals will be observed right near the state line, with somewhat higher snowfall totals located over southern Michigan, and somewhat lower totals over far Northwest Ohio and Indiana.  A general 2-4 inches will fall over far Northern Indiana and Northern Ohio (north of Route 6), with around an inch in areas south of Route 6, with much higher totals of 6-12 inches over Lower Michigan into Detroit.  This forecast is highly uncertain as storms like these seem to surprise meteorologists in what they do, so this will be situation that I will be watching.  There is the possibility that the storm shifts south, with more substantial cold air advection in the area, causing a earlier changeover to snow and more substantial snowfall amounts.  I still see this as a possibility, but then again we would still have to worry about warm boundary layer temperatures (the layer from the surface to about three thousand feet above the surface), which would melt the snow causing a cold rain.  One thing that would help the possibility of wintry precipitation is initially dry mid level air, which with intense lifting, would cause intense cooling in the middle and lower layers of the atmosphere.  This would cause the atmosphere to become marginally unstable, causing convection, with initial rain from the convection changing over to snow.  This is why I would also expect some areas to see thunder and lightning with any convective band of rain or even snow.  If this forecast changes, I will write another post to update it.

Experimental Forecast Page.

I have created an experimental forecast page on the blog.  Anybody can access it by clicking on the tab on the front page.  I will try my best to update it at least once a day, while in severe weather or winter weather situations it will be updated two or three times a day depending on how busy I am.  Sometimes if no changes are needed, I will update the forecast only every other day.  Generally I will post a five day forecast, but if I am crunched for time, usually a two or three day forecast will appear.  If you have any questions e-mail me at storm_reportsjoshua@yahoo.com.