Possible winter weather in the Mid-South tomorrow - what to expect

UPDATED 9PM SUNDAY:

Shortly before 9pm CST, the NWS in Memphis issued a Special Weather Statement for the metro, as well as all of northeast AR and west TN.  Here is the content of that statement:

...LIGHT WINTRY MIX EXPECTED LATE MONDAY MORNING AND AFTERNOON...

A DEVELOPING LATE FALL STORM IN THE LOWER MISSISSIPPI RIVER
VALLEY MAY BRING A BRIEF PERIOD OF A LIGHT WINTRY PRECIPITATION
MIX TO PORTIONS OF EASTERN ARKANSAS...THE BOOTHEEL OF MISSOURI AND
WESTERN TENNESSEE FROM LATE MONDAY MORNING INTO THE AFTERNOON.
LIGHT ACCUMULATIONS OF SLEET...SNOW...AND/OR FREEZING RAIN ARE
ANTICIPATED BEFORE TEMPERATURES WARM ENOUGH FOR A CHANGE OVER TO
ALL RAIN. ONLY MINOR TRAVEL CONCERNS ARE EXPECTED...ON MAINLY
ELEVATED SURFACES AND BRIDGES.

That doesn't mean you have to act like this guy!

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ORIGINAL POST:
Very cold air resides over the Mid-South as anyone who ventured out for even a few minutes today can attest to.  With a high of only 38 and a low of 24, this was the coldest day in Memphis since the first couple days of March.  It should be no surprise that Mid-South meteorologists are on high alert and poring over computer model data as a low pressure system moves out of the Gulf of Mexico into the southeast U.S., trailed by an upper level system - a favored setup for winter weather.  Those computer models have had a hard time locking in on a solution however, which makes for a difficult forecast.  Since there is no one computer model that seems to be the best right now, I'll show data from the high-resolution NAM as I describe what we expect.

The basic setup is described above, but a couple of additional factors play into the forecast.  First, very dry air in the lowest several thousand feet, all the way to the surface, will serve to delay the onset of precipitation until probably mid-morning Monday.  Temperatures at that time (after a low just below freezing) should be in the mid 30s. Rain should be the predominant precip type, however due to the dry and cold air above, some sleet could mix with the rain for a few hours, or until about lunchtime. No significant accumulation of wintry precip is expected in the morning as road temperatures are still well above freezing and precipitation should be mainly rain and not heavy.

A 3-D view of temperature and dewpoint at 9am Monday shows temps flirting with the freezing mark up to about 6000 feet, then above freezing from ~6000-8000 feet. With temps so close to freezing in the lowest levels, a mix of precip types is possible.

The high-res NAM model shows the possibility of sleet along the northern part of the precipitation area in the Mid-South at 9am.

After the initial shot at winter precip, the Mid-South should see all rain (though cold rain) through the afternoon and evening hours with temps likely remaining in the upper 30s all day. Overnight, as temperatures start to cool slightly and the main brunt of the precipitation begins to pull away, rain may again change over to a sleet/snow mix. Once again, as in the morning, precipitation should be light and tapering off and temperatures should remain right at or slightly above freezing, so no major issues are expected Monday night. Lingering flurries or sprinkles are possible Tuesday morning.

The high-res NAM model shows rain as the precip type at midnight Monday night/Tuesday morning though a light wintry mix is possible after that time as precip departs.

Overall, this is not expected to be a major winter weather event in the Mid-South, though some nuisance winter precip is possible Monday morning and again overnight Monday night into early Tuesday morning. Don't be surprised to see light sleet or snow.  This system moves east and likely becomes a nor'easter on Wednesday, so those with travel plans for the Thanksgiving holiday will want to keep an eye on flight times, especially in/out of the Northeast U.S. and Mid-Atlantic, where delays or cancellations could stack up.

Cold weather will continue in the Mid-South Wednesday and Thanksgiving, though sunny skies are on tap. A warming trend leads us into Black Friday and next weekend. Click here for the full MWN holiday week forecast.  Be sure to follow us on Facebook and Twitter for the latest on the winter weather scenario over the next 36 hours (links below).

--Erik Proseus, Meteorologist

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