Severe Storm Threat Tues. Detailed Analysis Here. Zone Option. JT. #ILWX

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Forecast Discussion:

EVENING – OVERNIGHT: An area of high pressure remains in place today, but we are closely watching an area of low pressure develop across the southern Great Plains. This will be the focal point for the zones 6/7 over the next 24-48 hours.


This evening and overnight I do think some of these clouds will move out and some clearing will occur. However, but late tonight into early Tuesday morning a warm front will be approaching the forecast zones from the south. This will likely increase clouds late tonight with perhaps a shower possible across zones 6.

TUESDAY: Through the daytime hours Tuesday the warm front will lift northward across zones 6 & 7 allowing for the return of southerly winds and warm air. Some of the short-range guidance suggests the warm front barely makes it across I-70 with temperatures in zone 7 only in the 50’s. However, the EURO and GFS models take the front farther north spreading 50’s to mid 60s into the region!


As the warm front lifts north through the day rain and a few t’storms will be possible through the morning.


A cold front will start to move in from the west Tuesday afternoon. This will enter western Illinois after 12-1 PM. Along this front a higher probability for rain and thunderstorms will exist.


While initially severe weather may not be a big concern extremely powerful upper level winds will move in across the region by 2 PM. Winds at 500 mb will spread in from the southwest at 85-95 mph.


Low in the environment 850 mb winds will race in from the southwest at 60-70 knots. Through the afternoon these winds will only prove to increase.


As storms develop along and possibly ahead of the front Tuesday they will have the potential to tap into this upper level wind and bring/mix them down to the surface. Also with winds increasing with height it will provide an incredible amount of shear which is needed for severe weather.

While instability overall for tomorrow looks low it will not take much for storms to get going, much like what happened on 12/23/15. However, with southerly winds in place, some strong moisture advection is anticipated with dew points rising into the mid 50’s to around 60 across the zones. So this moisture will help aid in storm development as well.


With this being said, the threat for severe weather looks to extend as far north as Springfield. However, the better threat looks to be from I-70 southward.


By 4-5 PM the front looks to be moving eastward across central Illinois with rain and t’storms being possible from central Illinois eastward into Indiana. At this time some of these will be capable of being strong to severe with damaging winds and isolated tornadoes being the main threat.


By 7-8 PM Tuesday evening the front will be moving into very eastern Illinois into Indiana. While some rain and storms will be possible along the IN/IL state line most of the region will be out of the risk for storms.


Non-thunderstorm winds on Tuesday will be strong with gusts of 40-50 mph possible!

Regarding new rainfall totals .25-.50” looks more common across the region a few localized areas could see .75-1” totals under the heavier thunderstorms.


While the majority of the rain will shut off by 9-10 PM into the overnight Tuesday into Wednesday a few rain showers will remain possible. However, temperatures through the night are anticipated to remain above freezing until closer to Wednesday morning. So any remaining precipitation is anticipated to remain in the liquid form.

WEDNESDAY: The area of low pressure and cold front will move off to the regions east and northeast. However, there will be enough moisture left for clouds to form and even some light precipitation to remain possible. Initially this will start as a few rain showers or sprinkles.

Through the day temperatures will remain just above freezing, but dew points will fall below freezing so any remaining showers or sprinkles may changeover or mix with snow by late morning through the afternoon. Overall snowfall accumulations look to be minimal to none with maybe a dusting across northern portions of zone 7.



Highs on Wednesday will be in the upper 30’s to upper 40’s early, but will fall into the low to upper 30’s late.

THURSDAY – FRIDAY: An area of high pressure looks to ridge into the region Thursday. This will allow for calmer weather for Thursday and most of Friday. Partly cloudy to mostly sunny skies are forecast to end the week.


Highs will be in the 30’s on Thursday, but warming into the 40’s on Friday.