FXUS63 KILX 070735 AFDILX Area Forecast Discussion National Weather Service Lincoln IL 235 AM CDT Mon Apr 7 2025 .KEY MESSAGES... - Cold temperatures will be in place this morning with lows near the freezing mark. Even colder temperatures are expected Tuesday morning with temps dipping into the 20s. A freeze warning is in effect from midnight tonight until 9 am Tuesday from Rushville to Danville south where the growing season has started. && .DISCUSSION... Issued at 225 AM CDT Mon Apr 7 2025 COLD START TO THE WEEK... Early this morning, low pressure is located over far northern lower Michigan with a cold front extending southwest across northern Illinois into Iowa. High pressure is located over the southern Great Plains with ridging extending across central Illinois. Favorable radiational cooling across central Illinois under the influence of the ridge axis is allowing temps to fall down to near the freezing mark and frost to develop. This could impact sensitive vegetation where the growing season has commenced, particularly across the southern half of the state. The cold front will push south across central Illinois this morning with high temps running about 10 degrees colder today compared to yesterday. Highs will range from the mid to upper 40s along the I-74 corridor to mid to upper 50s south of I-70. With the placement of the surface ridge axis cutting off any significant moisture return, expect the front to pass through most of central Illinois dry. Cold air advection behind the front will drive steep low level lapse rates with very weak SBCAPE of 25-50 J/kg developing. This may allow for a few sprinkles to develop, especially near the I-74 corridor. High pressure will build across the Upper Midwest overnight and shift into Illinois early Tuesday morning. This will set the stage once again for favorable radiational cooling conditions within an even colder air mass. Ensemble probabilities from the both the HREF and NBM show near certainty (100%) for temps to fall below freezing across all of central and southeast Illinois. The probability for a hard freeze (temps less than 28degF) are roughly 50% (south) to 70% (north) from the NBM. RAIN RETURNS MIDWEEK... As we reach midweek, upper level pattern is characterized by modest ridging over the West Coast and troughing in the east. An upper level disturbance digging across the Upper Midwest in the northwest flow will drive surface cyclogenesis with a deepening surface low expected to track from the mid Missouri Valley Wednesday morning across central and northern Illinois Wednesday night. Surface high over the mid Atlantic coast will extend southwest into the Gulf during this time with unfavorable low level trajectories for any significant moisture return into the Midwest. Guidance suggests dew points will only build into the 40s across central Illinois with passage of the midweek system. Prefer to see mid 50 dewpoints in order to support severe weather, so despite the close proximity of the low track and otherwise favorable kinematics, does not appear we will be able to achieve much in the way of instability to support severe weather. A few storms cannot be ruled out with MLCAPE values advertised by the GFS up to around 250 J/kg with forecast soundings also showing some weak elevated instability. NBM mean 24-hr QPF runs only around 0.2-0.3 across central Illinois Wednesday with 90th percentile values (showing a reasonable high end forecast) running roughly half an inch to just less than an inch. Highest precip amounts are expected near the low track along and north I-74. Lingering low level cyclonic flow will support some additional light rain chances on Thursday, then cold air advection driving steep low level lapse rates will support additional scattered showers Friday. High pressure builds across the region next weekend allowing a break from the precip with warmer temps gradually spreading into the region from the west behind the ridge axis. Deubelbeiss && .AVIATION... (For the 06z TAFs through 06z Monday Night) Issued at 1154 PM CDT Sun Apr 6 2025 VFR conditions will prevail through the period. The main concern this TAF period is the timing of a cold front which will shift winds from southwesterly to northwesterly, with gusts to 20-25 knots behind the front. This wind shift is expected to occur from north to south between 12-15z. Scattered diurnal Cu should develop today around 4-5 kft. Winds trend lighter after 00z, out of the northeast. Erwin && .ILX WATCHES/WARNINGS/ADVISORIES... Freeze Warning from midnight tonight to 9 AM CDT Tuesday for ILZ040>057-061>063-066>068-071>073. && $$