Weather Lookup

Key Messages

- light rain chances (20 to 50%) expected tonight into thursday morning, though rainfall totals will remain light at under one tenth of an inch.

- confidence is increasing for a significant heavy rainfall event late friday into saturday, focused across central and east- central wisconsin.

- another round of showers and potential thunderstorms towards early next week.

Discussion

Issued at 141 PM CDT wed sep 16 2026

Light rain chances (20 to 50%) return tonight into thursday morning: cloud cover will increase this evening as weak overrunning moisture moves in ahead of a shortwave moving east across southern canada. Rain chances tonight generally range from 20 to 50 percent, but precipitation will be light with 90th percentile amounts only up to 0.10 inches. Spotty light showers or drizzle will linger into thursday morning before clearing develops thursday afternoon. Seasonable high temperatures ranging from the upper 60S to middle 70S are expected today and thursday.

Heavy rainfall potential friday through saturday: heavy rainfall late friday into saturday represents the most significant weather hazard during the 7-day forecast period, with increasing potential for localized flooding across central and east-central wisconsin. Shortwave energy advancing across the rockies will trigger a 30 to 40 knot low-level jet directed into central wisconsin friday afternoon into friday night. Strong dynamic forcing will overspread the region, characterized by upper-level divergence in the right rear quadrant of an upper jet streak, robust mid-level frontogenesis, and strong moisture convergence above the returning warm front. Precipitable water values are forecast to climb to around 1.70 inches, which sits near the 96th percentile for mid- september. Warm cloud depths in excess of 12,000 feet will favor efficient rainfall processes.

Models continue to struggle with where the heaviest axis of heavy rain will occur. There are some signs that an initial band across the far north on friday afternoon associated with 700mb frontogenesis would subsequently push the second band on friday night further south away from our area. However, there are still signs the main band of heavy rain would drive through the heart of our area. This makes predicting rainfall amounts an issue as the nbm still seems too high with a mean value around 3 inches. The previous forecast amounts of 1 to 3 inches along with the probabilities still seem reasonable with the caveat that these features need to be resolved before higher confidence can be assigned to where the swath of heavy rain will end up. If the same locations that received heavy rainfall earlier in the week get the swath of heavy rainfall, antecedent soil moisture remains high, elevating the threat of localized urban and small stream flooding. Severe weather risk remains low due to meager instability, with most unstable capes generally under 500 j/kg.

Additional rain chances early next week: following the departure of the aforementioned system, a brief break in precipitation is expected sunday as weak surface ridging passes over the great lakes. However, the progressive mid-level flow will keep the region in an unsettled regime heading into early next week. Another upper shortwave trough and associated surface system will approach from the great plains toward sunday night and monday, bringing additional chances for rain showers and scattered thunderstorms through tuesday.

Aviation

For 18Z taf issuance issued at 1209 PM CDT wed sep 16 2026

Few-sct diurnally driven VFR cu will continue this afternoon then dissipate around sunset. Light winds below 10 knots are also expected. Clouds will increase and lower tonight as a shortwave approaches. Light rain chances increase after 04Z thu over central and north-central wi (kauw, kcwa, krhi) and after 07Z thu over eastern wi (kgrb, katw, kmtw). Handled with prob30 groups given the low probability for rain to hit the individual sites. Cigs will deteriorate to MVFR across central and east-central wi overnight, becoming VFR late tonight into thursday morning. Mostly clear skies and light winds will then prevail across the region on thursday.