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Boston Marathon Forecast: Raw, Rainy Monday Will Create Challenging Course

BOSTON (CBS) – Sometimes, the weather is like a box of chocolates - you never know what you're going to get- especially well in advance here in Boston.

Runners training for the big race constantly wonder if Mother Nature will be cooperative for the big day. The Boston Marathon temperature variations can fluctuate in a range of more than 40 degrees from year to year and as much as 20-30 degrees from one end of the route to the other.

Save Marathon History
(WBZ-TV Graphic)

The proximity to the cold ocean compounds the variety. You have to be prepared for almost anything and we've seen it all from snowsqualls to heavy rain to sizzling heat and humidity. Fortunately, these extremes are relatively rare but it looks like this year's conditions will fit into that category.

Welcome to those who have traveled to Boston from other parts of the country or world for this amazing race. Sightseeing in the Hub this weekend will become a disappointment if you desire nice warm weather.

2017 Marathon History2
(WBZ-TV Graphic)

That exited yesterday and now we await a strong cold front dropping down from northern New England to produce crashing temperatures later this afternoon and tonight. As a strengthening high-pressure system moves to eastern Canada, there will be a rush of very cold air southward through New England. Consequently, the region will be freezing tomorrow in record cold weather for mid-April.

2017 Surface Analysis
(WBZ-TV Graphic)

The main concern will be ice, not snow although some flakes may mix in as far south as extreme northern MA tomorrow morning. A band of a few inches of snow cannot be ruled out over the far northern mountains. A significant ice storm is NOT likely but ice pellets plus a glazing created by freezing mist and freezing rain is possible so DPW crews may be out treating some of the roadways primarily near and west of the I-95 corridor. Be cautious because the potential exists for slippery surfaces such as steps, sidewalks, driveways, parking lots, etc.

2017 Slippery ice
(WBZ-TV Graphic)

It will be cold enough so the maximum temperatures at both Boston and Worcester will likely beat the previous records for the lowest high temperatures for April 15th. The official highs for the day will occur just after midnight and it will continue to grow colder so the morning through mid-afternoon readings may only be in the 31-35 degree range! This may mean that the Red Sox game will get postponed due to the cold, the mist, the rain and the sleet!

2017 RPM Timeline Temps Local1.png2
(WBZ-TV Graphic)

Now to the main event! Conditions will start out cold and misty with passing showers of heavier rain from time to time The temperatures will gradually rise from the middle to upper 30s through the morning to the lower to middle 40s from midday through the afternoon. The milder lower 50s will probably remain south of the marathon route. The heaviest rain is most likely by mid-afternoon to early evening when some embedded lightning and thunder may occur. It is likely this will have the greatest impact on runners in waves 3 and 4.

There will likely be more of a headwind through much of the morning from the east-northeast. It will not be too windy at the start for the elite runners and starting waves but the wind will increase as the day wears on and with closer proximity to Boston. Some gusts over 40 mph will be possible during the afternoon especially underneath some of the passing heavier downpours. The wind should also veer slightly to more east or east-southeasterly but it is certainly never going to be a tailwind.

In conclusion: It is going to be a challenging and difficult day on the course. There may very well be some hypothermia cases to monitor. Do your best to stay warm and dry!

GOOD LUCK to one and all!

2018 Marathon Forecast MAP
(WBZ-TV Graphic)

MARATHON MONDAY FORECAST

7 a.m. Monday
Hopkinton: 36 degrees, cloudy and drizzly. Wind ENE 6-18 mph.
Boston: 38 degrees, cloudy and drizzly. Wind ENE 10-20 mph.

9 a.m. Monday
Hopkinton: 37 degrees, clouds and showers. Wind E 10-20 mph.
Boston: 40 degrees, clouds and showers. Wind E 10-25 mph.

11 a.m. Monday
Hopkinton: 38 degrees, cloudy with scattered downpours. Wind ESE 10-25 mph.
Boston/Fenway: 41 degrees, cloudy with light rain showers. Wind ESE 12-25 mph.

1 p.mMonday
Hopkinton: 40 degrees, scattered downpours. Wind ESE 15-30 mph.
Boston:  42 degrees, scattered downpours. Wind SE 15-35 mph.

3 p.m. Monday
Hopkinton: 42 degrees, heavier showers. Wind SE 15-25+ mph.
Boston: 45 degrees, heavier showers with embedded thunder/lightning possible. Wind SE 15-35+ mph.

5 p.m. Monday
Hopkinton: 44 degrees, downpours with embedded thunder. Wind SE 15-35 mph.
Boston:  47 degrees, downpours with embedded thunder. Wind SE 15-35+ mph.

Follow Barry on Twitter @BarryWBZ

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