Friday, March 21, 2014

Unsettled weekend weather is the transition between spring and yet more cold

We've been enjoying beautiful springlike weather lately and this looks to continue with one more fantastic day in store today before the weather begins to make significant changes. We'll start the weekend out with rain and cloudiness from one cold front before another stronger frontal passage makes for quite a chilly start to the week. Let's take a look at some specifics via the GFS weather model.

GFS model precipitation between 1-6am Sunday, About 1/4" of rain is expected.
A low chance of showers appears late Friday night into early Saturday with the first front that will knock highs down from the 70s Friday to the lower 60s Saturday. Then on Saturday night we see precipitation associated with the next approaching cold front occur within the Mid-South. We're not expecting a whole lot of rain with this front with totals of less than a quarter of an inch depicted by the GFS.  However, behind this front, temperatures will remain in the 50s Sunday with a gusty wind that will make it feel much cooler - and a far cry from the 70s of today.

GFS height anomalies (departure from normal) at 500 mb (18,000') valid at 6 AM Tuesday. Upper level pressure is well below normal from Canada into the Mid-South.
Monday remains cool, but likely dry, but moving on to Tuesday, we see a large trough (area of lower pressure in the upper atmosphere) spread across the eastern US. This indicates cold air streaming into the region from Canada, making conditions a good deal cooler this time of year than we normally experience.

GFS surface temp departure from normal valid at 7 AM Wednesday. The eastern half of the nation looks to be much colder than normal on Wednesday morning courtesy of the upper level trough.
By Wednesday morning the entirety of the eastern US is engulfed in abnormally low temperatures for late March. The GFS suggests that the Mid-South will see temperatures more than 20 degrees below average Wednesday morning, which would put the region near freezing with frost likely on Bradford Pear and daffodil blooms. While not bitterly cold winter air, it is definitely quite cold for what is supposed to be early spring.  The average last freeze for Memphis occurs March 22, so this would only be a few days later than normal (IF this were the last freeze of the spring - and we certainly hope so!).

GFS near-surface wind speeds/direction valid at 1 PM Tuesday
Lastly we have a near-surface wind map which shows winds speedily coming into the Mid-South during the day Tuesday from the north. This is the cause of such cool temperatures for late March.  We should probably be glad that we aren't further north as the system you can see above off the South Carolina coastline will likely end up being a late season Nor'Easter that could bring strong wind and cold rain or snow to the Northeast U.S. late next week!

You can check out the full MWN forecast here, although most are not too excited to hear that winter is not giving up just yet!

-- William Churchill, MWN Social Media Intern
-- Erik Proseus, MWN Meteorologist

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