Record Warmth Today/Heavy rainfall Tonight and Tomorrow.

Today's Forecast:

Latest RAP forecasts indicate temperatures will begin to infringe upon the 62-65 degree range by the middle of the afternoon today, especially across NW Ohio. This will only enhance convective cloud cover, which will develop by late afternoon in the vicinity of the cold front. Due to the warmer temperatures, instability, albeit very weak, could be slightly higher, allowing for greater rain and thunderstorm cover later tonight. While mid-level instability will be rather weak, and low levels still rather stable, I do expect the potential for at least an isolated embedded thunderstorm in the main precipitation shield.

The above image is that of RAP forecasted surface temperatures at around 3 or 4 p.m. today.  According to the RAP most, if not all of the area will hit at least 60 today, with the possibility of a few isolated spots reaching 62-65. As for the bottom image, that is the RAP forecasted sounding for the same timeframe. As you can see (for the avid weather enthusiasts out there), the sounding indicates little or no instability across the region. But the fact of the matter remains that this sounding is misleading about thunderstorm potential tonight and tomorrow for several reasons. One, when the onset of the precipitation begins, dynamic cooling, as well as evaporational cooling, will not only cool the mid levels, but it will also contribute to strengthening lapse rates. Take a closer look at the blue line. That blue indicates the thermal profile, after complete saturation commences purely from evaporation cooling. As you can see, there will be two primary regions of enhanced mid level instability, which will aid in the development of low-topped convective cells (thunderstorms) in the midst of the area of heavy rain. Another thing we must take into account is increased low level cold air advection, especially at 850 millibars, which will help strengthen lapse rates (enough possibly to allow for a brief period of surface based thunderstorms. But at this point, it would be extremely unlikely).

This is the 12z NAM's radar reflectivity forecast. This is for 1 a.m. tonight. As you can see, it is expecting a large area of heavy showers and thunderstorms to approach the area tonight. Now, comes the hard part. This event will be influenced strongly by mesoscale forcing, as well as forcing from the main upper level trough, cold front, and associated jet streak. Based on current forecasts, the strongest vertical velocities (how fast the air moves upward) will move into the region by the early morning hours, probably around 2 or 3 a.m. This will help to maximize rainfall rates, and possibly lead to flooding areawide. Other forcing factors include the mesoscale jet streak circulations, convective slantwise instability (especially when the cold front moves through Sunday mid-morning). If these factors can be maximized across the area (like the NAM is indicating), a good portion of the area will see 1"+, and a narrow corridor could experience rainfall amounts of 2-3 inches, especially along the Route 24 corridor.

As you can see, forecasted rainfall amounts will approach the 1-3 inch range across the area. The bottom image indicates the high amounts of moisture that will be involved in this system. This is one of the main factors in the reason for heavy precipitation tonight and tomorrow.

As for the details on the precipitation type concerns, it is still rather unresolved, but from the latest data of the NAM and RAP models, it looks as if the transition from rain to sleet/snow will occur in the early afternoon hours on Sunday. Although it won't accumulate more than a half an inch, it could lead to icy roadways.

After that, expect dry, cold conditions to remain for the rest of the week. After that, models are currently narrowing down a timeframe for a significant cold blast, which, if it were to happen, would break hundreds of records across the United States. In fact, the latest 12z GFS indicates 850 mb temperatures to drop below -30 across the area! (note: the 18z GFS and 00z GFS also showed the same thing, for the same timeframe). While I do not expect it to get that cold, it is possible that the area sees temperatures below zero at times. I'll keep you informed on this developing situation!