Slow Moving Upper Level Low to Bring Rain, Snow & Cold Air To End The Week!

Updated: Tuesday, October 6th, 2020 @10 AM

Valid: Tuesday, October 6th, 2020 @ 10 AM

Forecaster: James Follett

Cock a doodle do! A very good Tuesday morning to ya all!

You’re going to want to take advantage of today’s gorgeous weather as we will see sunshine up and down, side to side, and temperatures getting up into the mid and high 15’s!

The only place that will see some showery activity is Cape Breton this morning with a few showers but that will clear out by noon.

The nice weather is all thanks to a nice big dome of high-pressure and it will be departing on it’s flight tonight for a vacation as we are going to be in for a very unsettled rest of the week with rain, snow, wind, & cold.

So here is the FutureCAST that will take us out over the next 84 hours. A big area of high-pressure in control today. Then, as we get into the later evening hours of tonight, we will see some drizzle and light showers develop over the South Shores and this will continue into much of the day Wednesday over much of the province. This will be the light stuff. It’s not until we get into the evening hours of tomorrow and overnight when the heaviest rain will begin to fall.

A series of small low-pressures are getting caught up in a cut off low that will act as a jail cell and will merge them to create an intensifying low-pressure system developing North of Cheticamp Cape Breton. As this system continues to intensify and race towards Newfoundland later on Thursday, the winds will change to the northeast, which will funnel in some very cold air temperatures 5000ft above at 850mb is between -6 and -10*C, which is well cold enough to support some snowfall. We also have 1000-500mb thickness levels that will reach as low as 522-528. Thickness levels help indicate the type of airmass! So, for example, 522 is considered polar air mass, 540 is the rain/snow line, and this is what we use a lot in the wintertime to determine the rain/snow & mixing line. Most often, anything above 540 is usually rain and below 534-540 is snow. Then, there is 570 which is a Tropical/Humid airmass. This is when you get the hot & humid days because the air mass is very likely at or above 570.

For this system, the airmass will be very cold at 522-528 which is well enough to produce snow along with the very cold 850mb temperatures. Day time surface highs will also be on the cold side where highs will struggle to get above 5 degrees.

The best chance to see snow is very late Thursday night into Friday morning and will continue into Saturday. Now, it is still a bit too early to determine the snowfall amounts but the latest model runs of the ECMWF & GFS continue to put significant snowfall near 10cm. Other models have closer to 5cm but what looks very certain is that a good white coating is very likely for much of western Cape Breton. The further south you go, the less snow you will see. Much of Cape Breton could likely see only a few centimetres.

Now the Rainfall!

While Western Cape Breton will see snow Friday & Saturday, everyone else will see on and off rain, some heavy at times into the weekend. Especially, if you’re also in Cape Breton! The heaviest moisture looks to skip much of the West and head for Eastern Cape Breton. There is a very good agreement with the models on seeing as much as 50 mm or 2 inches of rain by the end of the day on Saturday in Cape Breton.

For elsewhere in the province, a good swatch fo 10 to 20 mm is expected. However, there are some pockets of potential 30 mm over Digby County.

So for tomorrow, from Yarmouth to New Glasgow, look for only Drizzle or Light rain on Wednesday. Then, by Wednesday Night into Thursday morning, that is when the heaviest rain will occur.

As we get into Thursday, we’ll see that moderate to heavy rain taper off to light rain & drizzle by noon hour. In fact, it’s very possible that we could clear out by noon and have a great afternoon Thursday. However, rain will continue for Northern sections.

By Friday, we will see drier conditions for much of the province with the exception of Cape Breton & Antigonish. Much of that area will see Drizzle or light rain but for Cheticamp and surrounding areas over Western CB near the coast, you can expect some Flurries or Wet flurries. As well, some steady light snow Thursday Night into Friday Morning.

Here is the latest look at the rainfall forecast starting Wednesday and it goes through until Saturday. For much of the province from Yarmouth to Antigonish, expect 10 to 20 mm. However, there could be some locally amounts up to 30 mm. For Amherst and surrounding areas, 20 to 30 mm with locally amounts up to 40 mm can be expected. And lastly, where the rain is expected to be the heaviest, look for 30 to 50 mm or 1-2” of rain and locally, some amounts could approach 75 mm or 3”.

The Winds…

The winds will also be a bit of a story. We will see Gusty and Breezy winds from Wednesday into Saturday.

Winds today are going to be ok and some what light with possible breezes to 20 km/h. However, they pick up tomorrow! Starting off gusting to 30 km/h in the morning, they increase to gusts of 40 km/h near noon in the Tri-Counties. By mid to late evening, gusts will be approaching 50 to 70 km/h on the South Shores and Tri-Counties.

Once we get into the overnight hours into Thursday, the winds really pick up! They’ll be gusting to 70 and possibly 80 km/h, then they’ll begin to die down as we get into late morning hours of Thursday. The strong winds push off to the north towards the rest of the province.

By Thursday afternoon, winds over Cape Breton will Gust between 80 and 100 km/h, with highest winds over Western Cape Breton near Cheticamp. Over the extreme northern tip of Cape Breton, winds are likely to gust upwards of 110 km/h.

Wind gusts will diminish under 80 km/h over Cape Breton Thursday night but will remain gusty to 75 km/h over Cape Breton on Friday morning. Meanwhile, gusts across the remaining areas of the province on Friday will be between 40 and 60 km/h.

Just look at these warm upper level temperatures at 850mb drop like crazy by Thursday! We go from a mild 8-10 degrees to near -8 degrees by Thursday. We do slowly recover by the weekend though! However, for Cape Breton and Newfoundland, the cold air looks to stick around through Thanksgiving!

And it will be a very cold late week, especially in Cape Breton. Winds Gusting near 100 km/h with rain at times heavy, and air temps below 5 degrees. We’re going to see those wind chill factors drop below freezing.

Ok, here is your Forecast!

Starting with Halifax & Halifax Metro:

A gorgeous day today! Lots of sunshine and temperatures seasonal for this time of year. We’ll see rain move in for Wednesday, warmer air comes in before the crash! Upper 10’s to near 20! Showery weather persists for Thursday and Friday to end the week, which turns much colder as those winds swing from the North East, then from the North West. 14 Thursday and only 10 on Friday!! We clear it out on Saturday and are slightly milder at 13 with a chance of showers Sunday. And Thanksgiving Monday looks dry and cool with highs of 12.

For Cheticamp and surrounding areas:

Not a pretty picture! Some showers today and 14 degrees. 14 tomorrow with a chance of rain and thunderstorms. This will be warmest day in a while! It keeps on raining into Thursday and down to 10 & 4 on Friday with Rain to Snow or a Rain/Snow mix. It’ll be windy! Winds will be gusting to 100 km/h. Flurries persist into Saturday and a high of only 5, starting the day near freezing. Sunday, we still have precipitation falling and some rain showers. Milder! A high of 8 and still very cool for this time of year. However, gorgeous sunshine for Thanksgiving Monday and we’re still at 8 degrees.

By way, the last time it snowed in Cheticamp was back in 2018, only 2 years ago on the 18th of October and it snowed 2cm. In Yarmouth, the last time it snowed in October was also 2018 on the 18th! A trace of snow and then again in 2015 on October 18th, another trace!

So, snow in October, especially around the 18th and 28th is not as rare you might think!

Finally, here is your Yarmouth County Forecast and the rest of the Tri-Counties.

Sunny and mild today at 16. Showery weather Wednesday, Thursday, & Friday. 16 Wednesday, drops to 12 on Thursday, and only 11 on Friday! Windy also for all 3 days.

Long weekend looks like this; some fog and clouds on Saturday and 13, 16 and some drizzle and clouds on Sunday. And for Thanksgiving Monday, look for back to sunshine and a bit cool out there at 14.