Marine Weather and Tide Forecast for Urbana, IL

DISCUSSION
Issued at 359 AM CDT Mon May 12 2025

Early morning WV satellite imagery depicts a deepening trough carving into the western US, with a cut-off low still positioned over Louisiana. Model guidance remains in excellent agreement that the former will help dislodge the latter, with the closed low expected to open/lift toward the Tennessee Valley by Tuesday. As this evolution takes place, an influx of Gulf moisture and synoptic ascent will overspread Illinois. The net effect will be diurnally- driven showers both today and Tuesday, and perhaps an isolated thunderstorm as instability builds in the vicinity of the cold-core low. In addition to the scattered showers, the synoptic pattern will be quite favorable for cold air funnels, and the normalized NST parameter continues to flash values > 1 both this afternoon and Tuesday afternoon, per recent RAP & NAM guidance.

Precip chances become muted by Wednesday once the upper trough departs toward the Mid-Atlantic region and subsidence works into Illinois ahead of an amplified ridge. Temperatures will become seasonably hot (mid 80s) on Wednesday beneath the ridge axis, and hotter still by Thursday (about 90) as a warm front surges north across the region in tandem with an upstream lifting/pivoting shortwave trough. In fact, Thursday's forecast at Peoria will threaten a 130-year record (93 degF, 1894).

The severe weather signal for Thursday remains poorly resolved by mid-range global guidance (GFS/ECMWF). While the synoptic pattern alone supports deep convection across portions of the Midwest, there are plenty of mitigating factors looming that continue to apply a downward pressure on predictability. Residual capping across the warm sector, dry air entrainment in both the low- and mid-levels, and displacement from the main upper forcing suggests updrafts could struggle to reach the LFC on Thursday, especially with only modest frontal forcing positioned beneath an otherwise less favorable right-exit region of the upper jet core. On the other hand, a stout EML, very steep mid- level lapse rates, and an increasing belt of westerlies atop the front will offer CAPE/Shear profiles that impress professionals and noobs alike.
This all adds up to a conditional severe weather threat for central Illinois on Thursday. Both the 00z GFS & ECMWF largely muted convective initiation across SE Iowa and W Illinois, while only about half of their respective ensemble members indicated convective initiation. This is in stark contrast to recent MPAS guidance which convincingly points toward organized, all- hazards convection across central IL Thursday evening. At this point, it's a true boom-or- bust scenario and either narrative is about equally likely. The best we can do for now is monitor trends as we eagerly await the hi-res CAMs to begin resolving the pattern with finer detail.

Depending on how Thursday evening unfolds, there is another conditional risk of severe weather Friday evening near and south of I-70. More or less, if convection erupts Thursday evening across east central IL, the front and any convective outflows will probably favor redevelopment just south of our CWA by Friday evening. By contrast, if it's crickets around here Thursday evening, the front may stay a little further north near I-70, putting our southern counties at greater risk of severe weather Friday evening.

A ridge of high pressure begins to nose across the Plains by Saturday, offering a drier and more stable forecast. Unsettled weather is then quick to creep back in by early next week, with both the GEFS & EPS offering some dirty-ridge, nocturnal-MCS action.

MJA

AVIATION
(For the 12z TAFs through 12z Tuesday Morning)
Issued at 528 AM CDT Mon May 12 2025

Clouds will increase and gradually lower today as an upper-level disturbance lifts into the region from the south. We have added a PROB30 for thunderstorms for all terminals except KPIA, with the best signal coming between roughly 18z-00z. Ceilings will continue to lower tonight into Tuesday as the upper-level disturbance creeps into SE Illinois. A gradual lowering to MVFR (07z-09z) and then IFR (09z-11z) is anticipated overnight amid a persistent east wind.

MJA

ILX WATCHES/WARNINGS/ADVISORIES
None.