Friday, January 31, 2014

A close look at potential winter weather on Sunday night

We've mentioned on social media that there are perhaps multiple scenarios in the coming week in which winter weather is possible. The first of those will be Sunday. We'll take a look at that in just a moment, but first what to expect between now and then.

Leading into Sunday, a very warm day is expected Saturday with highs near 60 and low rain chances.  Saturday night, rain is expected to move in as a cold front arrives between 9pm and midnight.  The front will cause temps to fall overnight to the mid 30s.  It appears that the overnight wave of precipitation will move out Sunday morning, so we expect that precipitation will remain all rain into Sunday morning despite it being cold.

During the day Sunday, we had thought a few days ago that it would be dry. Models are now painting a wetter picture as the front stalls just south of us and an upper-level low moves into the region. Temperatures should remain in the 30s, but above freezing, most of Sunday until the sun goes down so we're again expecting all liquid precip and a cold day.

By Sunday evening, as temperatures fall near the surface and aloft, there is a decent chance that precip will change to some wintry form before tailing off overnight.  In fact, leading to this measured degree of confidence is the fact that 3 of the major weather models that go out that far all show some form of wintry precip. Our best guess (subject to change of course) is that during the Super Bowl rain will mix with sleet and/or freezing rain, then to snow/sleet as temps continue to slowly fall, especially in west TN and eastern AR.

Total expected precipitation through Monday morning as forecast by the Weather Prediction Center. An inch of liquid -equivalent precipitation is possible across the metro, including Saturday night and Sunday's rain and Sunday night's mixed bag. Graphics courtesy WeatherBell.

Below you will see a couple of model graphics for midnight Sunday night that basically show a mixed bag of precip types in the area.  The top one is from the GFS, the bottom from the NAM (graphics courtesy WeatherBell).  The NAM seems to be showing some rain still around, but it also places the 32 degree line (in red) south of Memphis, so we believe it's precip type is a little off.

GFS model of precip type at midnight Sunday night. Green is rain, orange is sleet, pink is freezing rain, blue is snow.

NAM model of precip type at midnight Sunday night. Same color scheme as above.
Another interesting product to use comes from the NWS Winter Weather Desk at the Weather Prediction Center.  They produce probabilities of various winter weather events among other products.  The graphics below show the probability of measurable freezing rain (0.01"+) and 1" of snow in the 24 hours between noon Sunday and noon Monday (though precip should be gone by Monday morning).  Notice the freezing rain probabilities are fairly low (20-30% in the metro), but the chance of 1" of snow is decent, especially along and north of I-40 (higher than the ice probabilities anyway).  And of course these are probabilities of 1" occurring, so we can assume that the probability of ANY snow occurring (based on these graphics) is higher.

Freezing rain probabilities from the Weather Prediction Center from noon Sunday through noon Monday.

1"+ snow probabilities from the Weather Prediction Center from noon Sunday through noon Monday.
We're still 48-60 hours away from this potential event, so there obviously is still a degree of uncertainty, but the signals are present. We'll also continue to monitor the daytime hours Sunday in case models trend colder as moisture looks to remain in place.

After this event, Tuesday also looks wet, but warm enough for rain with precip moving out overnight as temps fall. The chance of wintry weather is fairly low Tuesday night. Cold weather sticks around and there could be another chance of mixed precipitation by Friday, however that is a week out so a lot can change. Stay updated with the latest info by following our social media channels and of course get the latest current metro conditions and the MWN Forecast via our mobile apps and website (all linked below).

--Erik Proseus, MWN Meteorologist

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