#ILwx Zones 3/4 – Heavy rain possible into Thurs, gusty winds as well? FROST potential Friday, eyeing big cold front mid-next week! Kirk.

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Key Points – Wednesday, October 19, 2016 – mid-next week


Good Wednesday morning and welcome to another Zones 3/4 forecast update! A much different story outside this morning compared to the last few days…currently, the norther 2/3rds of Illinois are in the lower 50s to upper 40s, while portions of Zone 3 are still seeing some 60s and even near 70 down south.

(Current temps)


Today’s main weather driver will be a stationary front that will be lifting from south to north, beginning in Zone 3 this morning and continuing into tonight and Thursday. We currently have some spotty showers across Zone 3 already early this morning, coverage will expand, especially later this morning into this evening as seen below via the HRRR.

(HRRR model loop)


We mentioned yesterday that we were not impressed by all of the models except the Euro and the NAM going south, and wouldn’t you know they all came back north this morning with the heaviest precip over the next 48 hours. Here’s what the NAM has for late tonight into Thursday morning. You can see that coverage will expand north into southern Zone 4.

(NAM tonight into Thursday AM)


We do have a marginal risk for stronger storms today into tonight…right now, our real main concern will be with some gusty winds, localized flash flooding and small hail.

(Marginal Risk today)


As you can tell below, the showers slowly move off to the east across Zones 1 and 2 in Indiana tomorrow morning and afternoon, but we still expect showers and some storms to be hanging around the eastern portions of Zone 4/3 by late tomorrow morning and early afternoon.


We like to use relative humidity at 700mb to forecast when the front will be passing, and as you can see below we expect all clouds and showers to clear by Thursday evening into the overnight.

(Front passes, skies clear Thursday PM)


48-hour rainfall totals reveal, as we mentioned yesterday, that 1-2″ rainfall totals will not be out of the question (localized higher amounts possible) especially across Zone 3 into Thursday afternoon. Zone 4 really doesn’t get on much precipitation at all from this stationary front, so rainfall totals will be on the low end especially the further north you live in Zone 4.

(48 hour rainfall totals)


Friday we clear out as higher pressure sets in, allowing temps to get below normal for a change! Right now we are expecting highs to be in the lower 50s north and potential hitting 60°F in southern Zone 3…so about a 10° spread from north to south.

(Normal temp departures…blues indicate below normal)


(Friday’s high temps)


As we pointed out though, that frost potential is there especially across northern Zone 4 on Friday. Here’s a forecast temp graphic indicating mid to upper 30s possible for Friday morning…so keep that in mind as we get closer to the forecast period.

(Frost potential Friday morning)


High pressure sets in this weekend, bringing plentiful sunshine and temps returning back to near-normal if not slightly above for Zones 3/4. 

(High pressure this weekend)


Early next week high pressure and pleasant conditions will persist across the Zones. We are still eyeing the potential for a moderate to strong cold front to push through the area come Wed-Thurs next week as we have noted the past days. There looks to be some strong winds at the 850mb level (5000 ft up), which will could signify some gusty winds as this cold front pushes east…just something to keep in mind as we get closer. Also don’t forget, we have been targeting the 27th from our BSR methods for a few weeks now for a potential front to pass through…so it’s nice to see it verifying for us!

(Mid-next week storm system)


(Low-level jet stream kicking up next week…gusty wind potential?)


Thanks for checking out the latest Zones 3/4 update…make sure to check back this afternoon and the rest of this week for more updates!


Today’s Video (6 min):

Confidence and Risk:

  • We have high confidence a stationary front lifts south to north initially across Zone 3 today into tonight, bringing the potential for heavy rainfall.
  • We have above average confidence in 1-2″ rainfall totals with localized higher amounts possible especially across Zone 3 over the next 48 hours.
  • We have high confidence the front pushes east late Thursday into early Friday, ushering in below normal temps for Friday
  • We have above average confidence high pressure sets in this weekend into early next week, allowing for average to above average temps to settle in as well with plentiful sunshine and dry conditions
  • We have average confidence right now of a cold front pushing through the Zones Wed-Thurs next week, that could bring some moderate rains and gusty winds

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