By Terry Eliasen, Meteorologist, WBZ-TV Exec. Weather Producer

BOSTON (CBS) – In a way, running a marathon can be similar to planning a wedding. You put months and months, perhaps even years, of time and effort into planning and preparing for the big day, but there is always one gigantic variable that will remain out of your control – the weather.

No matter how long or hard you have trained, if Mother Nature is in a bad mood on Marathon Monday, it can really foul things up.

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In 120 years of running this great race, we have truly seen it all with regards to the weather. Snow squalls, powerful winds, frigid temperatures, driving rains, oppressive heat, you name it, it has happened.

In fact, just look at the last 10 years!

(WBZ-TV graphic)

(WBZ-TV graphic)

In 2007, rain nearly canceled the race. 2-to-4 inches of rain fell the night before, and while it tapered off by race time nearly the entire Hopkinton Green was under water!

In 2012, temperatures reached an incredible 87 degrees, prompting race officials to offer deferrals to those folks who wanted to opt out and run again in 2013.

(WBZ-TV graphic)

(WBZ-TV graphic)

So what is the “ideal” day for a runner?

It depends on who you ask. But the typical response is cloudy and cool, upper 40’s or low 50’s with a tail wind. While April might seem like the perfect time to run in Boston, with temperatures averaging right in the sweet spot, it is still rare to get a “perfect” day.

This year will be no different. We are entering into an atmospheric traffic jam. We call this setup an “Omega Block.” Essentially, the jetstream becomes extremely elongated and the entire atmosphere becomes blocked. While parts of the country receive days and days of clouds and rain, others are parked in just the right spot. For once, it appears that we here in New England will actually have a good parking place, right under a ridge in the jet, meaning high pressure will sit over us for several days.

You may have seen a 7-day forecast recently with a string of suns on it? You can thank the Omega Block for that.

So, it is smooth sailing here right through the weekend. No chance of any precipitation and temperatures by Saturday and Sunday will grow warmer and warmer, likely topping 70 degrees by the end of the weekend!

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MARATHON MONDAY FORECAST

Here’s where things get interesting, naturally just in time for Marathon Monday.

It appears as though Monday will start sunny and warm. Temperatures in Hopkinton will soar quickly into the 50’s and 60’s by mid-to-late morning. It’s the same deal along the race course – mild west-southwest winds (generally a tail wind) will heat things up fast. From Framingham to Natick to Newton, temperatures will climb hour-by-hour well into the 60’s by midday.

At the same time, a “back door” cool front will be sliding southward from Canada and northern New England. Timing this front is the most important and difficult portion of the Marathon forecast this year.

If the front moves quickly, it would mean a sharp change in wind direction (to an onshore wind) along the race route and also a drop in temperature. No doubt, this would be a favorable solution to most of those running.

If the front is slower, the southwest winds would remain throughout the race and temperatures would stay very warm, likely soaring over 70 degrees by early afternoon.

Unfortunately right now, the latter solution seems a bit more likely. Odds favor a warm run for the majority of folks running through early-to-mid afternoon. Some of the late starters and slower runners have a better chance of feeling a refreshing onshore breeze by mid-to-late afternoon in the Boston area.

Other than a brief sprinkle with the passage of the front, no precipitation is expected on Monday.

We will continually update this forecast right through race day, right here on CBSBoston.com, WBZ-TV and WBZ NewsRadio 1030.

And of course WBZ is the only place to watch the entire race on Monday.

Good luck to all those running – stay cool!

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Follow Terry on Twitter @TerryWBZ