Big weather changes imminent

Still tracking Saturday snow


DETROIT – This is the last of the 60° weather for a while ... enjoy it while it lasts, although showers will prevail the rest of the afternoon.

The rain should end by midnight as Cold Front #1 crosses the area, and it'll remain windy at least through that time, after which the wind will eventually settle down to "just" breezy conditions from the southwest at 10 to 20 mph. Skies should become partly cloudy between midnight and dawn, with lows dropping into the upper 40s (9° Celsius for our Canadian neighbors).

We'll see varying amounts of cloud cover and sunshine on Thursday as Cold Front #2 crosses the area during the morning, so let's just call it partly cloudy and windy, and be done with it. Highs in the mid 50s (12° Celsius), with a southwest wind at 15 to 25 mph. Thursday's sunrise is at 7:28 AM, and Thursday's sunset is at 5:09 PM.

Partly cloudy to mostly clear Thursday night, with lows near 30° (-1° Celsius).

Mostly sunny on Friday, with highs in the mid 40s (7° Celsius).

Increasing cloud Friday night, with lows in the low 30s (0° Celsius).

The Saturday snow remains on schedule time-wise, with snow developing during the morning and continuing into Saturday night. Highs Saturday should peak near 40° (5° Celsius). It's still too early to try and pin down snow amounts, for three reasons:

1) The upper level disturbance that will spawn this storm is still over the Pacific.  It won't be until it crosses the coast tomorrow that our land-based radiosonde network (weather balloon network) will be able to provide data about its dynamics and thermodynamics.  Hopefully by tomorrow afternoon, I'll start seeing some consistency in the models' handling of the system's path (I'm already starting to see some trending toward a common solution…can't wait to see tomorrow's models).

2) This storm will cross our area at the same time as it is intensifying.  It's relatively easy to predict snow amounts with a cyclone that is already mature and in a relatively steady state.  But take a storm that is changing as it moves overhead, and that throws a huge monkey wrench into the works.

3) Remember that the ground is still quite warm given the warm fall we've had.  Plus, the snow will be falling in well-above freezing temperatures, so it'll be a relatively wet snow.  This means that, as it falls and accumulates, it'll also compact (settle) due to its own higher weight resulting from the higher water content of the snowflakes.  The easy way to understand this is that the colder the temperature is when the snow falls, the lighter and fluffier the accumulating snow is, and the higher the temperature, the wetter and heavier the snowflakes are.  So the "usual" water to snow ratio I use for computing the snow amount based upon normally colder temps of 25° to 30° (-3° to -1° Celsius) won't work in this instance…I have to figure out a lower ratio to use.

Hopefully, tomorrow's computer models will converge into some agreement on this storm, and I'll be able to give you some confident southeast Michigan snow totals for Saturday. HOWEVER, there's good news for you hunters heading up north for the second weekend of firearm deer season: there is a great likelihood for some accumulating snow up there, which I know is good news for you.

Sunday should become partly cloudy, but it'll be windy, with highs only in the mid 30s (2° Celsius), and colder wind chills, obviously.

Becoming mostly clear Sunday night, with lows in the low 20s (-5° Celsius).

Mostly sunny on Monday, with highs in the upper 30s (4° Celsius).

Partly cloudy Tuesday and Wednesday, with highs in the mid to upper 40s (8° Celsius).

The long range computer models are in 100% disagreement on the Thanksgiving Day upper air pattern. It's too early to even try and speculate what the holiday weather will be, given that one model keeps us partly cloudy and dry, while the other model projects a solid soaking rain.

Stay tuned ...

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