March to come in like a lion for Mid-South

The weather over the first 10 days of March promises to be very active over the Mid-South. The primary event will occur Monday-Wednesday of next week and will bring heavy rain, severe weather, and possibly heavy snow to the south-central United States. Right now, it appears as though KY/TN will miss out on the severe weather and heavy snow but will likely get in on the heavy rain.

In my post ten days ago, I mentioned that a meridional and stormy pattern was likely for early March after the second half of February was inactive with a split-flow pattern that trapped arctic air in Canada. This bottled up arctic air is now ready to be unleashed and the first wave of energy from this highly baroclinic atmosphere will carve out a deepening trough over the weekend over the northern Rockies. By Monday morning, arctic air will plunge southward into the central Plains behind a cold front as mid- and upper-level energy round the trough over the Southwest.

Tropical moisture will stream northward ahead of this trough which will provide deep moisture and the potential for severe weather along the Gulf Coast ahead of this cold front. The developing surface low associated with this storm will rapidly intensify as the storm becomes negatively tilted and begins to slow down Monday night into Tuesday. An upstream cut-off storm (this weekend’s Alberta Clipper for New England) will lead to a “shortening” of the wavelength of the ridge-trough pattern. This wavelength shortening will allow the Gulf Coast surface low to rapidly intensify and allow tropical moisture to overspread much of the Mid-South.

Regions NW of the surface low may receive heavy wet snowfall (6+ inches) from this system as the tropical moisture gets thrown over the arctic air behind the storm. The exact location of this region of heavy snow is unclear, although the models currently suggest that northern AR, the bootheel of MO, and southern IL are a good bet. By Tuesday night, the wraparound snow should move over KY as the surface low departs. There remains much uncertainty regarding the ultimate track of the surface low which will determine how much rain and then snow may fall over the mid-South (the 12Z GFS showed a 8-10″ snowfall for KY, whereas most other runs have very little). While snow amounts are uncertain, the likelihood of a heavy rainfall (1-3″ possible) is pretty high due to the slow-moving nature of this storm. As long as the low track south of the Mid-South, any severe weather should remain south of our region as well.

A weaker piece of energy may spread some light snow or rain over the Mid-South later in the week.

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