#ILwx Zones 3/4 – Continued chances for showers/storms into weekend, cold-air funnels/small hail poss, severe wx next week? Kirk.

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Key Points – Thursday, September 29, 2016 – mid next week

FORECAST DISCUSSION:

Good Thursday morning and thanks for checking out the latest Zone 3/4 forecast update! Taking a look at the latest radar loop today, we can see our upper-level low continue to bring waves of rainfall over the eastern portions of both Zones 4 and 3.

(Latest radar loop)

codnexlab-1km-c_illinois-rad-ani24-201609291035-100-100-raw

As we progress today, we will see continued showers and possibly a few storms as this low pressure starts to come back west a bit. Along with these showers, cold-air funnels and small hail are both possible across the Zones. There will be periods of sunshine between waves, however…so that is in the forecast for today as well. Here’s how things are shaping up around the noon hour today…our main focus this morning and into the early afternoon will be the more eastern portions of Zones 4 and 3 as seen below. Some of these showers may be moderate to heavy at times, but only 30-40% coverage is expected today.

(Simulated radar between 11am-12pmCDT)

refcmp_uh001h-bwx_mw

Moving towards the 4pm timeframe, we see our coverage of rain expands more westward, impacting areas near Peoria, Springfield even down to folks around St. Louis. Embedded heavy showers, lightning, small hail and a possible cold-air funnel are not out of the question.

(Simulated radar around 4pmCDT)

refcmp_uh001h-bwx_mw-1

Nearing the 9pmCDT hour, showers and possibly some storms will range from Chicago, Kankakee, Springfield down to areas near St. Louis. These will not be widespread, but continue to be scattered in nature to around 30-40% coverage. Heavy showers, lightning, small hail and cold-air funnels are all possible.

(Simulated radar around 9pm CDT)

refcmp_uh001h-bwx_mw-2

Let’s take a look at a quick cloud cover loop, that shows the nature of these “waves” of showers and clouds will be off-and-on…at times there will be dark skies and showers, while others, peaks of sunshine and pleasant conditions persist.

(Thursday’s cloud cover loop)

08z-20160929_hrrrmw_prec_cloud

Friday we will have our greatest chance for showers and possible storms, cold-air funnels, small hail, lightning and some heavier bands of rain. Coverage will likely be 60-70% throughout the day across both zones. We cannot rule a few peaks of sunshine Friday in between bands of rain, as well…but these will be less likely.

(Friday’s showers/storm coverage)

refcmp-bwx_mw

Saturday we continue to have clouds and showers in the forecast, although a little less coverage is expected around 30-40%. These will be on-and-off most of the day, with slightly less coverage likely nearing sunset and into Sunday. Once again, cold-air funnels, small hail, lightning and some moderate to heavy rains are all possible with these showers. Peaks of sunshine will be possible in between waves of rain and clouds.

(Saturday rain coverage)

nammw_prec_radar_060

Sunday, our upper-level low that has been persisting over the Midwest the entire week will finally push northeast into Michigan. There will still be possible showers, especially across Zone 4, into Sunday morning, but we will get progressively drier as the day goes on. Sunday evening should be dry and pleasant across both Zones.

(Sunday drier times coming)

nammw_700_rhum_084

Total precipitation into the weekend will be heavier near the IL/IN border, with additional rains between 0.75-1.50″ possible (with localized higher amounts possible as well). Central areas of both Zones will likely see 0.25-0.75″ of rainfall into the weekend, with a few spots of 1.0″ or higher not out of the question. Folks more westward are more likely to see totals nearing the 0.10-0.25″ range. The nature of these storms won’t be widespread, nor will they be washouts…at times they could be heavy, but peaks of sunshine will also be possible as they pass.

(Rainfall totals through the weekend)

rainfall-totals-thru-weekend

Temperatures will be near normal or slight below normal over the next 3-4 days. Unfortunately (or fortunately, if you like warmer weather), the cooler temperatures won’t last. Next week we are eyeing the potential for a warm-up once again with above average temperatures expected most of the week across both Zones. 

(Warm-up next week)

gfs-ens_t2mamean_us_4

Lastly, we still wanted to mention the potential for strong to severe weather mid next week. Right now, our confidence is still low on the timing, coverage and intensity…but it looks right now like strong storms could be possible ahead of a cold front. Don’t forget, our organic forecasting methods using the Bering Sea Rule (BSR) has had this going on for weeks now, also seen below…so this outcome would not surprise us, but be right on time.

(Severe potential mid-next week)

ecmwfued-conus-180-c-500vor_white

(BSR has strong cold front around October 7th)

bsr10716

Confidence and Risk:

  • We have high confidence that our upper-level low continues to bring clouds, showers, isolated storms, possible cold-air funnels, small hail and even peaks of sunshine into Sunday.
  • We have high confidence that our higher rainfall totals will be focused near the IL/IN border into the weekend
  • We have high confidence we warm back up to above average highs next week
  • We have average to low confidence right now of a strong to severe weather threat mid-next week

Thanks for checking out the latest Zones 3/4 update today, check back this afternoon for an All Zones update!

Kirk.

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