#ILwx Zones 3/4 – Patchy Frost potential, Dominating high pressure, Heavy rain possible mid-next week? Kirk.

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Key Points – Friday, October 21, 2016 – mid-next week


Good Friday morning…I don’t know about you but these weeks towards the end of the year seem to be flying by ever faster! Taking a look at current conditions, we can see as we have mentioned all week that our folks in in northern Zone 4 are dipping into the 30s this morning…flirting with some frost potential. 

(Current temps)


How cold is it relative to this time of year? Here’s a temp anomaly map of the heart of the Country…western IL is in the 10°F or more below normal category!

(Current temp departure map)


Here’s a cool water vapor radar loop…I like to show this to indicate dry air working in (the dark colors closer to black). What this tells me is that temps will continue to drop this morning, as well as our weather will be dominated by high pressure today…aka cool, dry and sunny.

(Water vapor loop)


High pressure will be dominating our weather over the next 5 days into early next week…this will allow for mostly sunny skies, seasonal temperatures (maybe slightly above…dry air is easier to warm than moist air), and great Harvest ’16 conditions. With that being said, we will still feel a chill in the air today from the temperatures we have been experiencing the last couple of weeks. Our hi-resolution forecast models say both Zones don’t even get out of the 50s today…and I would tend to agree.

(5 day average of sea level pressure shows high pressure is consistent…look for the “H”)


(Today’s high temps)


The NAM forecast model has patchy frost potential especially across Zone 4 once again Saturday morning, so keep that in mind with outdoor plants and when planning any activities…bundle up!

(Saturday AM temps)


Here’s a great illustration showing the temperature average over the next 5 days…basically what this tells us is that we will see, on average, seasonal temperatures (if it were red it would be above, blue, below).

(5 day average temps)


Our next chance for a storm system comes mid-next week around Tuesday night into Wednesday, as warm front out ahead of a low pressure system looks to extend west to east across northern Zone 4.

(Warm Front Wednesday)


Our models have been consistent on this feature over the past couple of days, but right now I’d say our confidence is about average on timing, intensity and location. With that being said, it is common with warm or stationary fronts (as we’ve seen the past couple of days) to bring moderate to heavy rains at times, so that is not out of the question come Tuesday night into Wednesday.

(Warm Front Analysis)


As the low pressure speeds up moving west to east, a cold front looks to take over a our weather across both Zones comes Wednesday day into the evening, before pushing eastward Thursday.

(Wed-early Thurs cold front)


Here’s an early look at how our rainfall totals are setting up over the next 7 days…as you can see, this graphic is suggesting fairly high totals across northern Zone 4 due to the warm front setting up next week as well as a cold front sweeping through Wed-Thurs. Confidence right now is average with these totals, but I do feel more confidence in higher totals across Zone 4 as a warm front generally moves slower than a cold front…allowing for higher rainfall totals.

(7-day rainfall totals)


Thanks for checking out today’s Zones 3/4 update…on stretches where we have more quiet weather, I like to throw in a little education to the “why” of our forecast…I hope you enjoyed it!


Today’s Video (6 min):

Confidence and Risk:

  • We have high confidence high pressure sets in over the next 5 days
  • We have average to above average confidence in patchy frost across Zone 4 again tomorrow morning
  • We have above average confidence in seasonal temperatures through the next 5 days
  • We have average confidence in our storm system next week in regards to the timing, location and intensity
  • We have average confidence the highest rainfall totals set-up across Zone 4 via our warm front