Marine Weather and Tide Forecast for Holiday Shores, IL

SHORT TERM
(Through Late Sunday Afternoon)
Issued at 336 AM CST Sat Feb 28 2026

FIRE WEATHER TODAY:

While the more significant fire weather conditions occurred yesterday and conditions have improved, we aren't completely out of the woods in that regard as we may still see some pockets of elevated conditions lingering through this afternoon. As we approach sunrise, a weak cold front has settled into the area and stalled, and this feature is expected to remain roughly along the Missouri river through the day today. Meanwhile, a surface low is expected to slowly traverse this boundary today, and the associated pressure gradient will maintain breezy surface winds ahead of it. North of the front, these winds will be primarily easterly, while south of the front they will be largely southerly. In any case, sustained speeds of 10 to 12 mph with occasional gusts to 20 mph can be expected for the most part. Meanwhile, humidity values on either side of the boundary are likely to dip into the 25 to 35% range, in spite of the arrival of mid level moisture and cloud cover. Along the front itself humidity is likely to stay just a bit higher (and the fire weather threat lower) thanks to moisture convergence, but since this front may waver throughout the day, there aren't many areas that we can definitively say WONT see at least a brief period if elevated conditions. Not everywhere will, but there is at least a reasonable chance for this in all but perhaps a few areas of southwest Illinois where lighter winds are more likely.

Meanwhile, due to the aforementioned mid-level moisture and forcing from the surface low and subtle mid level shortwave, increasing cloud cover and widespread virga can be expected during the day, with perhaps a few pockets of light showers as well. The primary limiting factor here will be the persistent and deep dry layer in the lower levels, which will be difficult to erode (and also responsible for the continuation of a marginal fire weather threat).
Even where rain reaches the surface, it likely won't amount to much more than a hundredth of an inch or two.

Overnight, a more substantial cold front will surge southward through the area, along with a more seasonably cold airmass. While initially this won't have a significant impact aside from bringing our temperatures back to more typical values Sunday, it will set the stage for a late-season round of accumulating snow sometime Sunday night through Monday morning.

ACCUMULATING SNOW LATE SUNDAY / EARLY MONDAY

Driving this event will be the arrival of a compact mid-level shortwave along the leading edge of a southern stream jet streak, which itself will begin to phase with the polar jet somewhere in our vicinity. While the jet dynamics involved are somewhat complex and partially obscured by blended ensemble guidance, deterministic models reveal that this feature will generate some potentially robust mid-level frontogenesis and omega (vertical motion) as it arrives, which should drive rapid saturation and eventually drive precipitation to the surface. Exactly how quickly this occurs is a major forecast point, because as we have already established, very dry low level air will need to be eroded first. Model guidance remains somewhat split on how quickly this will occur, both due to differences in the degree of dryness that will be present, and also the strength of the forcing. However, while this may delay the onset time, eventually precipitation will win out and reach the surface in most areas, and likely by sometime Sunday night at the latest.

From here, the primary question will be the distribution of precipitation types, including exactly where and how much accumulating snow will fall. Before we get into what we don't know, we still expect that at least some areas will see accumulating snow, and likely enough to cover roads and impact travel. While there remains a lot of variability in this forecast, this aspect of the forecast has remained relatively consistent.

However, confidence remains relatively low regarding exactly where the heaviest snow will fall, and how much. This is due to a number of factors, but we will start with uncertainty in precipitation types and rates. Regarding the former, most forecast model soundings continue to support snow as the dominant frozen precipitation type, as we have not seen a significant warm nose aloft that would produce much more than brief pockets of freezing rain or sleet. However, this is not iron-clad, as many of these profiles remain near the melting layer for a significant depth, even when the upper levels do eventually cool into the dendritic growth zone. Meanwhile, some deterministic soundings do show the loss of saturation in the colder parts of the profile (-10 or lower), suggesting a possible transition from snow to freezing drizzle. Likewise, non-trivial ensemble probabilities for light freezing rain accumulations remain (20-40%) in both the NBM and LREF, so it can't be completely discounted. However, even if that did occur, we have doubts that road temperatures would be cold enough to support ice accumulations of such light amounts. Meanwhile, the presence of dry air will support wet-bulb cooling and a transition to snow, although this may require more substantial rates in order to be fully realized.

As for precipitation rates, there remains some variability regarding the strength of the forcing associated with the shortwave. However, most models continue to produce enough lift to drive accumulating snow to the surface, including potentially impactful amounts (75th to 90th percentile amounts of 3 to 4 inches). If any locations reach those higher amounts, it is likely to be within a relatively narrow corridor where the strongest forcing exists. We do not expect that these higher end amounts will be widespread, and there will likely be a significant difference in impacts where these amounts fall and where they don't, due to the fact that warm pavement temperatures are likely to quickly melt lighter snow amounts.

Finally, the last lingering source of uncertainty is simply the track of the shortwave. Model guidance appears to be trending a bit farther south with this system and likewise with the main corridor of accumulating snow, although there is still a wide range among both individual members and clusters. In general, global models and ensembles remain a bit further north, although even these (particularly the GEFS) have shown a slight southerly shift.
Meanwhile, early returns from some of the longer range CAMS have been much farther south, bringing the corridor of accumulating snow to right along I-70 and even further south. While we're not confident that these southern outlier solutions are valid just yet, it does reduce our confidence in the location of heaviest snow.

Snow (and rain) are likely to wind down sometime Monday morning or early afternoon, and attention then turns to the onset of an extended period of wet weather.

BRC

LONG TERM
(Sunday Night through Friday)
Issued at 336 AM CST Sat Feb 28 2026

While there will likely be a lull in precipitation sometime late Monday, this is likely to be short lived as our active pattern continues early Tuesday. On a synoptic scale, the upper flow pattern is expected to transition from zonal to southwesterly, which will put our region within an active storm track and persistent warm air and moisture advection. This is likely to produce multiple rounds of widespread rainfall from Tuesday through the end of the work week, including potentially some thunderstorms.

Between Tuesday and Wednesday, a potent shortwave will emerge from the Rocky Mountains and drive lee-cyclogenesis, and the resulting low pressure system will approach our area from the west. Ahead of it, strong southerly return flow will drive the northward transport of warmer air and rich moisture (95th+ percentile ensemble mean PWAT), which will likely be concentrated along stationary/warm front draped across our area. Due to the interaction of this moisture with the stalled front and steadily increasing upper forcing, rain is likely to steadily increase beginning early Tuesday and continue until the surface low arrives Wednesday. Exactly where this initial rain falls is somewhat uncertain and may depend largely on where the surface front stalls, but this becomes less of a factor as the low arrives and drives another round of rain. Meanwhile, ensemble guidance does produce some modest instability during this period, so at least a few thunderstorms will also be possible. The potential for strong/severe storms remains somewhat limited by modest overall CAPE values, but given the strong dynamics, this will need to be monitored. In any case, the potential for substantial, drought improving rain amounts exists in many areas Tuesday and Wednesday.
In fact, the ECMWF extreme forecast index output has begun to highlight Tuesday with a modest potential for more impactful rain amounts, adding more confidence to the potential for substantial rain. This likely won't be the last of it, either.

That's because another similar trough is expected to follow right behind the mid-week system, likely driving another round of widespread rainfall later in the work week. While confidence in the finer scale details is lower with the latter system, ensemble mean PWAT values once again climb above the 90th percentile in all available ensemble suites, and even to the 97th-99th percentile in the LREF. All that said, confidence continues to grow that most of the area will see substantial rainfall by the end of the week.

BRC

AVIATION
(For the 12z TAFs through 12z Sunday Morning)
Issued at 415 AM CST Sat Feb 28 2026

VFR conditions are expected throughout the 12Z TAF period. Winds are expected to be highly variable today as a low pressure system moves through the area, although speeds are generally expected to remain below 20kt for the most part. Overcast mid-level cloud cover is expected for most of the day today, with widespread virga and perhaps some brief, very light showers. Confidence in rain reaching the surface or causing visibility/ceiling reductions remains too low to include in the TAF at this time. A cold front will switch winds to north-northeasterly this evening and this will persist through the end of the period.

BRC

LSX WATCHES/WARNINGS/ADVISORIES
MO...None.
IL...None.