Wednesday, February 1, 2012

"See Text" - what text? Thunderstorm discussions on marginal days

UPDATE 2 (2:30pm): The Slight Risk area has been expanded and now includes the Memphis metro area (see map below).  The main threat is large hail through about 8pm. For more info, click here.
Updated slight risk issued at 2pm by the Storm Prediction Center.

UPDATE (10:30am): A Slight Risk area has been added for Arkansas, roughly south of I-40. The threat for hailstorms is higher in that area. The risk has not increased significantly in the metro. For more info, click here

Original Post:
As of 8am, the Memphis metro is under what meteorologists often refer to as a "SEE TEXT" area for this afternoon with regards to thunderstorm development. What the heck does that mean? And what text am I supposed to see, and what does it say?? First of all, check out the first graphic below from the Storm Prediction Center. These are the folks that issue the Slight/Moderate/High risk areas for severe thunderstorm potential. See the words "SEE TEXT" over the Mid-South in the graphic? This means that SPC believes there is a small risk for some type of strong storms, but not enough to post a Slight Risk. The accompanying graphics show where that risk lies and what the threats are. The "text" being referred to is the technical discussion from SPC, which can be found on their website at http://www.spc.noaa.gov/products/outlook/ - click on the outlook that includes the "See Text" area.

The SPC "See Text" area includes the Mid-South for Wednesday afternoon
So what about today's threat specifically? An upper-level disturbance and cold front will move into the area this afternoon. With plenty of low level moisture (dewpoints approaching 60) and a modest amount of instability, especially if we see some sunshine this afternoon that could boost temperatures to 70 degrees, the upper-level impulse will be enough to trigger some scattered convection. According to the graphics below, some storms could pose a threat of large hail and a damaging wind gust. The tornado threat graphic is not shown as it indicates there is almost no threat of tornadoes.

Hail outlook for today - 5% chance of severe hail
Wind outlook for today - 5% chance of severe wind
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