As of this morning, the driest month of the year (on average) has seen just over 7" of rainfall in 2009, more than double the average of 3.31". Unfortunately, we aren't done yet. With 3 days to go in the month and quite possibly one doozy of a storm system ahead, we will likely end up with one of the wettest Octobers on record. For the year, Memphis has received 51.28" of rain. After the next couple days, we will probably see our average annual precipitation total of 54.65" exceeded with two more months of 2009 left!
So, as for this much-anticipated, and maybe much maligned when it is all said and done, weather system, the pattern sets up like this... a strong mid-autumn cold front will be moving very slowly out of the Rockies (where Denver is receiving a whopping October snowfall today) towards the region over the next 48 hours. Meanwhile, Gulf moisture in advance of the system will begin streaming into the region over the next day as a warm front lifts into the Mid-South by Thursday evening.
The first round of precipitation, mainly in the form of showers with a small chance of thunderstorms, heads into the area Thursday morning. We'll then see the distinct possibility of scattered storms Thursday afternoon and night as the cold front approaches and the warm front lifts to our north, placing us in the "warm sector" of the system. The setup also favors the possibility of some damaging wind gusts in the stronger storms, thus we are under a SLIGHT RISK of severe weather for Thursday afternoon and night. The first real bout of potentially flooding rain will come just ahead of and then immediately behind the cold front late Thursday night into Friday morning. The potential for a couple of inches of rain exists with this round and you can also expect windy conditions during this time period.
The front then stalls just to the east of the metro area, but low pressure will form over the north-central Gulf and move along the front to the north-northeast on Friday night into Saturday. Unfortunately, it looks like the low will be close enough to bring another round of heavy rain into the region around the back side of the low. The potential for the heaviest rain right now appears to occur Friday night and Saturday morning, when another couple of inches are possible, however scattered light to moderate rain could last well into the day on Halloween. Fortunately, it appears right now (this being still 72 hours out) that the rain may make an exit so that trick-or-treaters can put down their umbrellas and pick up their candy bags! We'll cross our fingers!
In all, the Memphis area could see as much as 6" of rain (one model indicates maximum amounts of 8") between Thursday morning and Saturday evening! Thus, the Flash Flood Watch which has been issued for the entire region from Thursday afternoon through Saturday morning.
It's a good time to remind all of my readers that flash flooding can be deadly and this threat is real! Stay away from areas where rushing water exists, don't let children play near swollen creeks or drainage areas, and don't drive where water crosses the road. One foot of moving water is enough to pick up a car and move it downstream. Turn Around; Don't Drown!