Friday, January 3, 2014

Looking ahead to Sunday's Arctic plunge: snow & bitter cold

Temperatures in the lower half of the 30s today will feel like spring warmth by early next week, following an Arctic cold front that moves through Sunday morning. And certainly don't get used to the upper 40s expected Saturday!

Rain chances increase Saturday night ahead of the front being shoved across the eastern U.S. by a massive dome of cold air straight from the north pole.  Rain will be likely Sunday morning with temps in the 40s, however as soon as the front passes through (between 8-11am), cold air pours into the region and we'll reach the freezing mark by noon, if not a bit quicker.  When that happens, rain will change to snow.  The amount of moisture left behind the 32-degree line determine the amount of snow we get.  This is not a case of whether it will get cold enough, because it WILL be cold enough!

Current estimates from various computer models range from a heavy dusting (0.5-0.75") up to a couple of inches.  Our current forecast is for a good inch in the metro, more to the north and less to the south.  It is conceivable that some spots in the metro could see up to 2", however we believe that to be on the high side.  Rain should change to snow by noon with the heaviest prior to 3pm, then flurries possible into the early evening.

European model forecast of precipitation between 6am-noon Sunday and the freezing line at noon (dark blue). MWN believes the cold air might get here an hour or so quicker than this shows. Rain vs. snow is NOT depicted in this image.

European model forecast of temperatures at noon Sunday. Notice how quickly temps transition from 40s to 20s!
The other concern Sunday will be the rapid nature of the falling temps.  Rain that falls before temps reach 32 could quickly freeze on all outdoor surfaces and bridges/overpasses in particular could "flash freeze," meaning that sitting water turns to ice in very short order.  We expect to see temps in the 20s by late afternoon.

This will begin a period of below freezing temps that will last until Wednesday, or as much as 72 hours, including periods of extreme cold (for the South).  Low temperatures in the city will be near 10 Monday and Tuesday mornings, Monday's high will only be in the middle teens, and wind chills Monday morning will drop below zero!  Areas outside the city proper can subtract at least a couple of degrees from those morning low temps. It's been 4 years since we've had lows that cold and maybe as far back as February 1996 since we've seen highs in the teens.

European model graphic of forecast temps and precip through next week. Click for larger image.
Now is the time to prepare for winter weather Sunday and bitter cold for 3 days.  See the graphic below for information from the NWS on cold weather preparation.

Cold weather preparedness from NOAA.  Click for a larger view.
We'll have more information and updates to the forecast on our website, mobile web, and social media platforms, all listed below, in the coming couple of days.  In addition, plan to join us Saturday night at 8pm for a Google+ Hangout on our expectations for the coming several days.  You'll be able to watch live via Google+ or YouTube, or watch a recording after the fact.  Links will be posted on MWN and our social feeds.

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