Here is a quick update on the forecast for tonight and into tomorrow morning with regard to the threat for some wintry precipitation to mix in with the rain. So far things are playing out – roughly – about like we were thinking. Today it didn’t get quite as warm as we were thinking and there were a few wayward patches of drizzle and sleet – but there was a bit of flexibility with today’s high and drizzle was expected, sleet was not.
The NWS in Jackson has elected to extend the Winter Weather Advisory into Lawrence, Simpson and Smith counties. Details on that below.
A challenging forecast
Above are the two local weather balloons available for south Mississippi. One is out of New Orleans, the other is from Jackson. The data is from 6pm tonight. And we can compare those to what the model data suggests it should look like at the same time.
That is pretty close. It means, we can look at what the model thinks South Mississippi should look like and feel pretty confident that it has it right.
The important pas about the above image is the little blue line in the middle of the red line and the green line. That is the wet-bulb line. One day I’ll do a whole post on that. Today is not that day.
Instead, I’m going to zoom in really close and lay a yellow line over the blue-dashed line you can probably barely see in the chart above. And that will help me explain the wet-bulb line.
That yellow line on this chart is the freezing line. And, as many of you remember, this is a Skew-T chart and the axis is skewed to the side. And the red line is the temperature line and the green is the dewpoint line. The closer the red and the green, the more moist the air is and the further apart, the drier.
In this case, the atmosphere is pretty dry between about 1,000ft and 10,000ft. And it is well-above freezing since the red line is on the right side of the yellow line. That may not seem like good news for those who want snow.
But it kinda is, actually.
That little blue wet-bulb line is what the temperature would be in the atmosphere if all the sudden you filled it up with moisture. So, let’s say a little shower moves through the area and starts precipitating. It would cool the air all the way back down to below freezing in the same area that is – right now – well -above freezing!
That is why I’ve been saying that I think the precipitation starts as a mix of rain and snow and sleet. Because in the heavier showers it will fully saturate the air and allow some of the frozen precipitation to sneak all the way down to the surface!
How much will make it? It will depend on each individual little shower. That is why the forecast for your house may be different than your neighbor three streets over.
On the radar
Right now, this is what it looks like in Jackson:
Peaceful snowfall in Jackson, MS! 🌨🌨🌨❄️❄️❄️ #mswx #snow @NWSJacksonMS @PatrickEllisWx @spann pic.twitter.com/gqg21XJ8Yz
— Severe Weather MS (@SevereWeatherMS) January 11, 2021
Over on the radar:
You can see that precipitation is overtaking the area. Most of this is light to begin but can – and will – increase in intensity overnight and into tomorrow morning for south Mississippi.
Beware of ‘bright banding’ which is when the radar shows more ‘intense’ coloring for precipitation than is actually happening. There is a lot of science and math behind this, that I won’t dive into here, but know that things may look pretty intense on radar, but end up being a fair amount lighter in real life.
But these showers will pick up during the next few hours and I think the best bet to see any snow flying through the air is going to be in these first few showers that move through the area. Before the warmer air oozes into the region at the lower and mid-levels of the atmosphere.
So, between right now and about 1am is going to be your best bet to see any wintry precipitation.
The forecast for you
While I can’t give a county-by-county forecast for the entire region, here is a look at the county-by-county forecast for South Mississippi.
Simpson County
…WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON CST MONDAY…
11p – As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 2″ of a slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 33 and 36.
Smith County –
…WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON CST MONDAY…
11p – As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 1″ of a slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 33 and 36.
Jasper County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 1/2″ of a slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 33 and 36.
Clarke County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 1/2″ of a slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 33 and 36.
Wayne County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. No meaningful accumulations are expected during this time. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 35 and 39.
Jones County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 1/2″ of a slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 35 and 39.
Covington County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 1/2″ of slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 34 and 38.
Jeff Davis County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 1″ of slushy accumulation is possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 34 and 38.
Lawrence County –
…WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON CST MONDAY…
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 33 and 36.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. Up to 2″ of slushy accumulation possible. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 34 and 38.
Walthall County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 37.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. No meaningful accumulations are expected during this time. Temperatures will be between 33 and 36.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 34 and 39.
Marion County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 37.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. No meaningful accumulations are expected during this time. Temperatures will be between 35 and 39.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 35 and 40.
Lamar County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 37.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. No meaningful accumulations are expected during this time. Temperatures will be between 35 and 39.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 35 and 40.
Forrest County –
11p – Precipitation likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 37.
3a – Precipitation continues as a rain/snow/sleet mix, flipping back and forth between all snow, all sleet, all rain, and a mix of all three. No meaningful accumulations are expected during this time. Temperatures will be between 35 and 39.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 35 and 40.
Perry County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 39.
3a – Precipitation continues as a rain/sleet mix. No meaningful accumulations are expected during this time. Temperatures will be between 34 and 39.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 36 and 42.
Greene County –
11p – Precipitation will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 39.
3a – Precipitation continues as a rain/sleet mix. No meaningful accumulations are expected during this time. Temperatures will be between 35 and 40.
7a – Precipitation changes back over to rain – all rain. Any accumulations melt as temperatures will be above freezing still. Temperatures will be between 36 and 42.
George County –
11p – Precipitation will be all liquid. Temperatures will be between 35 and 40.
3a – Precipitation continues as a rain. Temperatures will be between 37 and 43.
7a – Precipitation continues as rain. Temperatures will be between 40 and 45.
Stone County –
11p – Precipitation will be all liquid. Temperatures will be between 35 and 40.
3a – Precipitation continues as a rain. Temperatures will be between 37 and 43.
7a – Precipitation continues as rain. Temperatures will be between 40 and 45.
Pearl River County –
11p – Precipitati will likely start as some form of a rain/snow mix – mostly rain. As precipitation increases in intensity, more snow will mix in with the rain and it may switch over to completely snow at times. Temperatures will be between 34 and 38.
3a – Precipitation continues as rain. Temperatures will be between 37 and 43.
7a – Precipitation continues as rain. Temperatures will be between 39 and 44.
The Bottom Line
Things are playing out just about like we’ve been thinking, no major changes to the forecast.
Overview
It still looks like rain will be the dominant precipitation type for South Mississippi. There will be snow and sleet mixing in at times. And it may even switch to full-on snow or full-on sleet at times, too. But the dominant precipitation stype looks like rain. And any accumulations will be few and far between and should melt by the morning commute on Monday.
Timeline
Precipitation, for some, will wait until after midnight. The first rounds will be light. and mostly liquid with a mixture of frozen precipitation, too – mainly north. Some spots may see snow falling at this time, too. It is going to be dependant on very short-term localized atmospheric conditions. Truly you could see snow and your neighbor five houses down may see rain.
By Monday morning around 7a, rain will be falling across the entire area. It may be heavy at times and temperatures will be around 33 to 40 degrees. In the heaviest rain showers, snowflakes may periodically mix in.
By Monday afternoon around 1p, rain may begin to mix with sleet – for some – again. That will happen mainly north and west.
By Monday evening around 7p, rain will be ending and leftover drizzle and light sleet may persist. A few flurries may be possible across the northern areas along I-20.
What to expect
Some organizations and businesses make may schedule changes to prepare for wintry weather. Schools may make preparations, too. Government offices may also change their hours and availability.
People are likely to buy up bread and milk – and if 2020 taught us anything, toilet paper. The grocery store may be busy this weekend.
In South Mississippi travel isn’t likely to be impacted by frozen precipitation, but roads will be wet so give yourself extra time to get from Point A to Point B. If you have to travel along, or north, of I-20 on Monday prepare for the potential for icy conditions and slower travel.
If you have a flight out of PIB, NOLA, Gulfport, or Mobile any time on Sunday or Monday it won’t be affected by frozen precipitation on the ground. If you have a flight out of Jackson or Meridian, your flight may be delayed (but likely only shortly) depending on how things shake out. Check with your airline before leaving home.
