Weather Alert Day: Dangerous cold expected this weekend, accumulating snow possible
The ABC17 Stormtrack Weather Team has issued a Weather Alert Day for Friday, Saturday, and Sunday as dangerous cold returns to the region. This may or may not coincide with accumulating snow as well.
SETUP:
The upper-level pattern late this week combines the northern jet stream we've been dealing with all week, with an additional jet stream from the South Pacific that develops in conjunction with an upper-level wave that's currently well out over the Pacific.
The confluence of cold and dry air from the north with moist and active flow nudging in from the south is creating potential for a winter storm nearby, potentially impacting mid-Missouri with cold AND measurable snow.
UNCERTAINTY/LIMITING FACTORS:
There is plenty of uncertainty remaining in the forecast, even as we begin to see guidance converge on the likelihood of a system bringing snow across the mid-south, starting in Oklahoma, and trekking to the East Coast. Mid-Missouri currently has a chance to see some of this snow, but several factors give us pause on getting too excited just yet. As mentioned above, the low that develops to our west, orienting the southern jet stream that sends waves of disturbances our way is still off the west coast. This system won't even be sampled very well for modeling until Thursday as it remains out at sea. The northern jet stream that sends small disturbances and weak cold fronts this week is set to make a bigger push of cold air around the same time as our southern moisture. This could combine the cold and moisture we need, but it could also keep critical moisture levels south of mid-Missouri altogether. If we get the moisture we need for snow, we look to likely reside on the northern edge of the system, removed from some of the best lift and moisture, which would set us up for lighter snow totals.
Additionally, the likely present cold and dry air at the lowest levels of the atmosphere could potentially eat away at snow as it falls as well. On the flip side of the coin, colder air could create higher snow-to-liquid ratios that could make snow accumulation more efficient.
A sign of all of this uncertainty is disagreement among models. Not only are the two big global models depicting very different tracks of snow, but they also differ on the strength of the upper low driving all of this, which is then driving uncertainty in the timing of the overall event.
There are signals for accumulating snow locally, but also reasonable cause for suspicion with our snow chances this weekend, and still a chance some get nothing. We'll continue to monitor and bring you updates. You should consider what accumulating snow could mean for your weekend plans. Below are the details we know so far.
TIMING:
It's going to be cold, possibly colder than it has been all season. Timing regarding the cold sets in Friday, behind a cold front that works in early in the morning. High temperatures look likely to come in the morning near 20°, before cooling into the teens by the afternoon, and low single digits if not near zero by Saturday morning. Cold persists until we warm into Sunday afternoon, when temperatures are once again forecast above 20°.
Should snow make it into the picture this weekend, chances begin at some point on mid-to-late Friday, then persist through at least Saturday midday to evening. Greatest chances currently look to arrive around midday Saturday, and taper into Sunday morning.
HAZARDS/IMPACTS:
Currently, confidence is low in snow, but if snow falls, it could be enough for accumulations and travel impacts. This element of the forecast may change rapidly. Stay tuned for further details.
Our greatest confidence is in extreme cold; with frozen pipes, car trouble, and frostbite possible with prolonged exposure this weekend. The window of deepest cold is from Friday morning through Saturday Sunday morning. Wind chills are tough to forecast at this distance, but are likely subzero at times, especially Saturday morning.
