SWOP Weekly Weather Discussion

HEADLINE

Near to slightly above normal temperatures will continue...with a strong signal for a significant rainfall event at the end of next week.

DISCUSSION

Northwesterly upper-level flow will temporarily bring temperatures back down to near normal in the lower to middle 50s over the next couple of days before west-to-east zonal flow signals the return of above normal readings well into the 50s and lower 60s for the remainder of the week.  Two storm systems imbedded within the flat flow will impact central Illinois over the next 7 days.  The first will skirt through the region late Monday into Tuesday, bringing scattered showers and a few thunderstorms.  Models continue to suggest the greatest instability and shear will remain south of central Illinois, so any strong to potentially severe storms will focus from the Ozarks southwestward to Texas.  Once this wave passes, a mild and dry day will be on tap for Wednesday before a stronger system approaches from the southwest by the end of the week.  Given the stronger deep-layer southwesterly flow ahead of the approaching wave, moisture profiles become much more robust than with the first system.  In fact, GFS precipitable water values increase to around 1.50 on Thursday, November 20th...which would be at climatological record values for the date.  With a dynamic system interacting with an impressive influx of moisture, confidence is growing that a significant rainfall event will unfold.  While it is still too early to pinpoint exact totals, early indications suggest beneficial amounts in excess of 1 inch everywhere (and perhaps over 2 inches along/south of I-70).  In addition, we will need to keep an eye on potential severe thunderstorms across parts of the area...as this system may spread greater instability and thus higher severe weather probabilities further north toward the I-70 corridor.  Stay tuned to future forecasts for more details.    

Both the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) are currently in a negative phase, but are progged to rise into positive territory by the middle and end of next week...supportive of above normal temperatures.  After that, all models show the AO and NAO once again becoming negative as we move into Thanksgiving week.  At this time, it appears probable that the next significant push of very cold air will arrive shortly after Thanksgiving.  

The latest 6-10 day outlooks (Nov 21-25) from the Climate Prediction Center (CPC) suggest ABOVE normal temperatures and ABOVE normal precipitation across central Illinois.

Issued: 11/15/25