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Boston Weather: 39.0°F | Fair

Weather: After the Storm

By Robert Korty
STAFF METEOROLOGIST -- If you followed the forecasts concerning last night’s snow you may have been baffled by waffling predictions. You are not alone. The main difficulty in forecasting the weather in coastal regions is resolving fine-scale processes from coarse-grid models. The weather may vary markedly over distances as short as 20 kilometers owing to strong contrasts in air masses over land and at sea. Yet our weather models typically solve the prognostic equations on grids that are spaced at least 100 kilometers apart. A major reason for such coarseness is the dearth of upper air measurements; we send balloons up to gather data only once every 12 hours and often several hundred kilometers apart.

Intense storms wrap warm air from the Atlantic Ocean up their eastern sides; whether the wind in Boston is from the northeast (off the Atlantic) or north-northeast (blowing down the coast) makes a huge difference in whether warmer maritime air may raise the temperature above freezing with a changeover to rain or colder air remains in place with all snow. Quite often it may be a near-certainty that there will be snow in Worcester, rain on Cape Cod, with a boundary somewhere in between (over Boston and Providence). Predicting exactly where the rain-snow line will land often proves difficult, leading to uncertain forecasts.

But today’s forecast is a bit easier (I hope) ...

In the wake of the storm, winds will be strong today from the northwest. Under clear skies, the temperature should rise to near 40°F (4°C).

Extended Forecast

Today: Becoming partly sunny and windy. High of 39°F (4°C).

Tonight: Mostly cloudy with scattered flurries. Low near 30°F (-1°C).

Wednesday: Partly cloudy. High near 45°F (7°C).

Thursday: Partly cloudy. High near 43°F (6°C).