Lincoln, Illinois

• Patchy drizzle late tonight into Monday morning may briefly reduce surface visibility to under 1 mile across central Illinois.

- Strong winds will ramp up midweek, with gusts reaching 20 to
  30 mph Monday and 30 to 40 mph Tuesday.

• A dynamic storm system brings a 50 to 70 percent chance of around 1.0 inch of widespread rainfall Tuesday evening, with localized amounts up to 2.75 inches.

/Near Term (Today and Tonight)/

Upper-air analysis depicts a split-flow regime over central Illinois early this morning, with a pair of compact shortwave troughs lifting across the Upper-Mississippi Valley and another translating across the Lower Ohio River Valley. Sufficient synoptic forcing--driven by both dCVA and gentle isentropic ascent--supports scattered showers into early afternoon. However, regional mesoscale soundings indicate persistent low-level dry air. Despite saturation in the 850-700mb layer, stubborn near- surface dryness will restrict coverage and intensity. While most locations receive between a trace and a few hundredths of an inch of precipitation, localized amounts up to 0.25 inches are possible where low-level dry air is overcome, consistent with 00z REFS LPMM QPF. Abundant cloud cover will hold afternoon temperatures in the low- to mid-60s, keeping forecasts 3-5 degF cooler than NBM guidance.

Showery activity should taper off this evening as subsidence and weak ridging build in behind the departing shortwaves. Nevertheless, the period from overnight into Monday remains favorable for patchy, transient drizzle. This is primarily driven by warm, moist isentropic ascent lifting poleward across the Mid-Mississippi Valley Monday morning, augmented by an embedded shortwave rippling ahead of a deepening low pressure system over the Nebraska and South Dakota plains. Given the lack of cloud ice nuclei, measurable rainfall will remain negligible. The greater impact could be on surface visibility, which could fall below 1 mile in spots if you believe REFS guidance.

/Dynamic Midweek Storm System (Monday Night through Wednesday)/

Forecast uncertainty increases by Monday night as the jet stream buckles over the central U.S., driving multiple mid-level shortwave troughs southward through midweek. Minor model discrepancies persist regarding trough phasing and precise frontal timing, though guidance consensus has converged on a Tuesday evening cold frontal passage across central Illinois.

As the synoptic low deepens and upper-level energy consolidates, the surface pressure gradient tightens significantly. EPS and GEFS mean wind gusts project peak speeds of 20-30 mph on Monday, increasing to 30-40 mph on Tuesday near the cold front. This dynamic system will draw mid-70s temperatures and a rich plume of Gulf moisture northward, pushing atmospheric precipitable water (PWAT) values near 1.75 inches--approaching the 99th percentile for early November climatology. NBM Mean 48-hour QPF supports widespread rainfall totals around 1.0 inch through 6 AM Thursday (50-70% chance), with high-end 90th percentile forecasts indicating localized totals between 2.0 and 2.75 inches.

A few severe storms cannot be ruled out Tuesday evening. Kinematic fields will be robust, characterized by 40-50 kts of bulk shear. Although model-derived thermodynamics remain modest (MLCAPE < 150 J/kg), a narrow tongue of 60+ sfc dewpoints is forecast to surge ahead of the front. Sporadic damaging wind gusts present the main threat; however, low-level hodographs exhibit an elongated loop, suggesting a conditional tornado threat if sufficient low-level instability materializes to promote stretching.

/Late Week (Thursday through Next Weekend)/

Uncertainty remains regarding how the primary upper low evolves late in the week. Ensemble guidance (GEFS and EPS) suggests the low may meander over the Great Lakes through Thursday before departing Friday. Should this materialize, daily shower chances will persist through Thursday along the systems slow-moving deformation axis. Following an abbreviated break in precipitation on Friday, another frontal system approaches next weekend, bringing additional rain chances and potentially frosty temperatures.

A dry sub-cloud layer will promote continued VFR ceilings through much of the afternoon while also limiting shower coverage and intensity. We are therefore only carrying a mention of VCSH in our TAFs today.

Ceilings will gradually lower throughout the TAF period, with MVFR conditions spreading from south to north between 20z-01z. Then, as warm/moist air continues to pile into the region from the south this evening, patchy drizzle is forecast to develop, prompting ceilings into the IFR/LIFR range overnight.

Winds will maintain a SE component today, occasionally gusting near 20 kts this afternoon.

None.