It’s hard for us to complain too much about the rain we’ve gotten here lately, since there seems to be an invisible line somewhere in eastern Middle Tennessee that cuts off the faucets before the bulk of the rain gets here. Consistently over the past 10 days, West and Middle Tennessee have gotten more rain than East Tennessee. In fact, there are unofficial reports out of Perry County and other Middle Tennessee areas this morning of an additional eight inches of rain received since late afternoon-early evening yesterday, and all of that activity died out before it got to us (and a pretty potent line of showers and storms this morning is quickly diminishing to little more than light rain as it moves east). But, complaining about the weather is one thing human beings have down to an art, so let’s do it, shall we?

The good news for this weekend is that the NWS’s Storm Prediction Center, while not ruling out severe weather for Saturday, no longer has us in an outlook box for the severe stuff. The latest outlook from the SPC:

ON D4 /SAT SEP 26TH/…CLOSED MIDLEVEL SYSTEM OVER THE MID MO VALLEY
IS FORECAST TO OPEN AND ACCELERATE EWD THROUGH THE UPPER GREAT LAKES
AND OH/TN VALLEYS. WHILE WIND FIELD WILL STRENGTHEN ACROSS THESE
REGIONS…THE PRIMARY UNCERTAINTY IS QUALITY OF WARM SECTOR OWING TO
IT/S ANTICIPATED NARROW /W-E/ CHARACTER AND THE LIKELY PRESENCE OF
ONGOING STORMS. SOME SEVERE WEATHER IS CERTAINLY POSSIBLE FROM THE
OH VALLEY SWD INTO THE CNTRL GULF STATES…HOWEVER CONFIDENCE IN A
MORE WIDESPREAD EVENT IS LOW ATTM.

Basically, positioning is all wrong. Also, the GFS model has backed off significantly from what it was showing yesterday. Just to take the two simplest values depicted by the GFS as an example, yesterday at this time the model was showing a Lifted Index of -3 for Saturday evening with CAPE values near 500 J/kg. Not significant, but not completely non-conducive for severe weather, either. Today, the model is showing an LI of +1 and much less instability for our area.

But even if we don’t see severe storms, that says nothing for the rain we’re probably going to see. I mentioned yesterday that the NAM guidance model — the North American Mesoscale model, which is a higher resolution model than the Global Forecast System (GFS) — was different from the GFS in what it was depicting for Saturday. But today it has come more in line with the GFS, and this is what it’s showing for the 24-hour period from 7 p.m. Friday to 7 p.m. Saturday (with almost all of this being Saturday afternoon):

The GFS, meanwhile, just continues to get stronger with this system, though it’s still keeping the bulk of the activity slightly north:

Of course, it’s important to remember, once again, that these models aren’t forecasts. They’re merely a tool that meteorologists use to make their forecasts. Because of the nature of these systems, you can’t look at those graphics and say, “Well, we’re going to receive 2 inches of rain in Oneida while Chattanooga receives only 1 inch,” based on what the graphics show. But, suffice it to say that it’s shaping up to be a wet Saturday with on-and-off showers and storms.

The National Weather Service continues to forecast a 50% chance of storms Saturday and Saturday night. The NWS in Nashville has bumped up their forecast to 60% for Saturday night. Given that we’re still 72 hours out, I think it’s almost a certainty that we see those predictions increase in probability as we get closer to the weekend.

NEXT WEEK: The latest GFS model run continues the idea of low 40s/low 60s for lows/highs from Tuesday-Thursday next week here on the Plateau.