Update - The National Weather Service has issued a Flash Flood Watch, scheduled to go in effect at noon for our area, and lasting through parts of Thursday as well. The showers and storms will become more prevalent during the afternoon, and any place that typically drains poorly will be susceptible once again. Given the current ground saturation, 1.5"-2" of rain in a 6-hour period or less is a good ballpark threshhold for sparking flash flooding. Feel free to continue to monitor the tracking maps below for the latest on what is going on weather-wise in the tri-state.
It's been that kind of week around here...Well, it was last week, and the fact that this week will be very similar makes the whole thing a little unusual. We often have to deal with a few days of the ole 'ring of fire' convection, but this has been an extended period of scattered storms and downpours. I hate using the same weather image to depict the skies on more than a couple days in a row-- because surely something's different about each day. But alas, the best way to describe things continues to be the same image. [See the 7-day image below].
While you're down there by the way, take a look at another attempt at revamping the blog for a more universal compatability. I've been trying to figure out a way to display all the storm-tracking maps that have often appeared at the bottom of each blog post, and I want to see some folks comment their opinions on how it displays now-- particularly from each camp of desk/laptop, tablet computer, and smartphone. I'm hoping to get a experience everyone can be satisfied with.
Okay, so on to the discussion of the forecast.
The best way to describe the weather pattern we're in here is by using the upper-level weather maps. Since there are few 'fronts' in the US and most of them are weak, the upper-level maps tell a much better picture of what's going on:
GFS - 500mb Chart - Tuesday Afternoon
I realize there's a lot going on here, but I'll try to explain with the help of all the things I've drawn on here. First, we've got the "Bermuda High" to our east, always known for it's influx of hot and humid air. We've got a thermal ridge "High" on the west coast, keeping temperatures in the 110s all over the place. The two are conspiring against the low pressure trough in the middle, keeping it locked in there and forcing it to just do its thing in-place: Funneling moisture in from the Gulf of Mexico and firing off storms. The yellow "X"s on the image are local maximums in the red blobs (also known as "vorticity maximums") that stir up trouble in the way of concentrated showers and storms. So, the main points here are several fold: (1) We've got a very stagnant pattern in place; (2) Whenever a Vort-Max "agitator rotates toward our region, expect an increase in thunderstorm coverage, regardless of time of day; (3) There is a lot of moisture in play from both the Atlantic and the Gulf, so expect downpours in any storm-- and with it the possibility of flash flooding.
Here is the current estimation of the next 48-hours of precipitation we'll be seeing:
The bummer about maps like this is when we're talking about thunderstorm convection these images are in effect smearing precipitation around to make these general contours, whereas the reality will be much more clustered, splotchy, and exceedingly hard to predict. Some folks will get hit by some 1-2" gully-washers, while others will see partly sunny skies the whole time, then fortunes may well reverse later in the day (just like yesterday). Current flash flood guidance would have a 2" rainfall in 3-hours time causing a lot of water problems-- this is possible in any slow moving thunderstorm or series of them over the same place. So be on your toes.
In time, the Atlantic ridge otherwise known as the "Bermuda High" will start to pinch in westward...
GFS - 500mb Level Chart - Sunday Morning
This is about the closest opportunity we've got to see the weather pattern break down and perhaps give us a breather from the seemingly ever-present risk of scattered storms. When the high creeps westward onshore and the thermal ridge in the west coast inches eastward, the two will crowd out the low pressure in between and cause it to fill in. This will remove at least one impetus for channeling in moisture and tamp down on the prevalence of those "storm agitators" roaming around. A consequence of this will be an increase in heat (and heat index). I suppose folks who have tickets to the final round of the Greenbrier Classic will have to temper their happiness at the better prospects for dry skies with the need to lather up on the sunscreen and keep those water-bottles coming.
Until then, it's a rinse-and-repeat weather pattern where we'll go through cycles of storms and sunshine. The entire tri-state area will be in this hit-or-miss pattern but overall everyone will have their turn. It certainly isn't the right time to be cutting and curing hay (unfortunately for the folks that have been asking about it).
Without further ado, here are those promised tracking maps to stay on top of things:
Have a great day everyone!