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Clipper season is upon us

LATE OPENINGS / CLOSINGS: Check here for the latest weather-related schedule changes.


After the morning fogs burns off the sun will come out for a few hours and temperatures will climb into the upper 40s. Clouds ahead of the next cold front will then enter the picture along with some precipitation that foreshadows a change in our overall weather pattern.

It’s that time of winter again…Alberta Clipper time! The large scale weather pattern has shifted a bit per an indicator known as the Pacific / North American Pattern. This parameter has been at or just below a zero value and is now climbing into the positive range. What this heralds is the elbowing of a persistent high pressure ridge from its previous position out over the Pacific Ocean to its new location parked over the West Coast.

The domino effect of this has been to kick the cold air outbreaks coming out of Canada a few hundred miles eastward. Now, instead of diving straight south into the southern Plains states and then scooting eastward the cold air outbreaks are aimed directly at the Mid-Atlantic. This effectively shuts off the Gulf of Mexico as a source of moisture for big storms to form and ride up the East Coast. But at the same time this setup opens the door for Alberta Clippers, which are small upper air disturbances that “surf” the jet stream and move into and out of our region very quickly.

The leading edge of this change will come later today into tonight in the form of a weak cold front that will spawn an equally weak coastal storm. The combination of the two will provide only light precipitation for Fredericksburg and vicinity which will begin late this afternoon as rain. As temperatures drop tonight behind the cold front the rain will turn to light snow showers but the chances of accumulating snow is small according to this excerpt from a Weather Prediction Center graphic:Fburg snow probsThe yellow shading over Fredericksburg represents less than a 10% chance of an inch of snow, which the local NWS Sterling forecast office agrees with as they call for less than a half-inch of the white stuff by morning.

After this a series of clipper systems will swing through the area, with one Friday followed by another one early Sunday and a third due through early next week. Each one will contain the chances for light precipitation which could be rain, snow, or a mixture. Forecasting the exact track of these quick-moving systems is almost as difficult as forecasting where a single thunderstorm will form during the summer, so stay tuned to the forecast.

Permalink: http://news.fredericksburg.com/weather/2014/01/15/clipper-season-is-upon-us/