Good evening! We'll have one more day of heat and humidity before a big pattern change introduces a taste of autumn into our region. We may also be dealing with effects from a potential off-shore tropical or subtropical system early next week.
During the day Wednesday, a cold front will be bearing down on western and central North Carolina. Ahead of this, hot and humid air will continue to pump into the region. Isolated storms are expected in the early afternoon, with a better chance of showers and storms in the late afternoon into the evening. I don't anticipate any significant severe weather, but a storm or two might pulse severe.
The front slowly moves into central and east-central NC Wednesday night into Thursday morning. I expect a fairly good coverage of showers and thunderstorms during this period. By Thursday afternoon the front should be approaching the coast. As for a severe potential, similar to Wednesday, one or two storms could be severe-warned, but on the whole, I don't see an exciting severe weather event occurring.
Regarding heavy rain, the storms, of course, could produce locally heavy rain. The potential is there for some places to pick up a good couple of inches of rain, which could lead to localized ponding and flooding of poor-drainage or low-lying areas.
The front clears the coast and is a memory by Friday afternoon. We can expect perhaps some morning clouds and maybe a renegade shower or storm, but otherwise clearing conditions and much, MUCH cooler and less humid.
An absolutely beautiful weekend is on tap as high pressure of Canadian origin keeps dry conditions and temperatures below to well-below normal. Meanwhile, there is the potential that a tropcial or subtropical system develops somewhere off the southeast coast, on the remnant trough. While this shouldn't directly affect our region, coastal areas may have an increase in cloudiness early next week with some showers possible. I believe we'll all experience breezy conditions as the tropical/subtropical low interacts with the strong high pressure ridge well to our north. Temperatures should continue to run below normal.
I like to sprinkle in some extras in these blog posts, so I thought I'd show some model graphics. The first one is the GEFS 2-meter temperature anomaly chart. This is the GFS ensemble (multiple runs of the GFS model with one or more calculations "tweaked" a little bit). The blue areas show the magnitude of the below-normal temperatures at 2 PM next Monday... as determined by our models. Is this gospel? No, of course not, but since the ensembles are all pointing in the same direction, it's a pretty good bet that it comes true.
The next graphic is more-or-less another way of looking at ensemble model data, the EKDMOS chart. A forecaster can examine EKDMOS charts for hourly temps, max/min temps, wind speeds, precip chance, etc. It's just one of the tools in a forecaster's toolbox. The EKDMOS is a graphical representation of model output. The green line with triangles represents the bottom value, or the 10th percentile (90 percent of models predict values HIGHER than this number). The blue line with squares on the end indicates the 90th percentile, meaning that 90 percent of the models predict values LOWER than this number. The red, of course, is the mean... the average.
The closer the bars are to each other indicate good confidence or good agreement amongst the ensemble of models. A wide spread, of course, indicates the very opposite -- a wide range of numbers shown by the model.
I have shown here graphs for Maxton/Laurinburg, and for the Wilmington International Airport. (Other areas are similar.) The Maxton graph shows the ensemble mean maximum temperature BELOW 80 DEGREES (!!) Sunday, Monday, and Tuesday, and ensemble mean minimum temperatures around 60 degrees Sunday night/Monday morning, and Monday night/Tuesday morning.
The ILM airport graph is similar, just a little bit warmer given proximity to the very warm (lower/middle 80s) ocean water.
Are these numbers gospel? No. Again, it's just one of our tools.
Finally, here is a graphic from the NWS Climate Prediction Center, which demonstrates the confidence on below-average, average, or above-average temperatures. The darkest blue represents a 70% chance that temperatures will be below normal. It does NOT demonstrate how MUCH below normal... it merely tells us, yeah, we're really confident that it's going to be cooler than normal.
My stoplight ImpactCast highlights Thursday as a day to avoid any outdoor plans. While the heat index won't be an issue, numerous showers/storms will pretty much wipe out the chances for lawn mowing or ball games, etc. Travel conditions get a yellow light as well given the potential for isolated flooding.
If you want to go to the beach tomorrow, for the most part you should be okay. Just keep an eye to the sky and if threatening weather approaches, take shelter. "When thunder roars, go indoors."
THERE IS A MODERATE RIP CURRENT RISK for Brunswick County and New Hanover County beaches (and points north).
Here are the remainder of your forecast graphics ... and like I said, this weekend is going to be spectacular. Get out and enjoy it!
Going to try something new here. I posted these slides on the Facebook page, but I want to try setting up a blog where I go into more detail regarding the forecast for the area. We'll see how this pans out.
Click / tap on each graphic to enlarge.
Without further ado...
We had a really hot day today (Friday) across the eastern Carolinas, with high temperatures well into the 90s and heat index values upwards of 110 in some spots. This is in response to a large heat ridge located over the southern United States this afternoon. This ridge will break down a bit and allow a trough to set up over the eastern third of the country.
A trough is typically associated with stormy (or inclement) weather conditions. In our case, a cold front will be pushing toward the eastern Carolinas by Saturday afternoon. This will be the spark that brings showers and thunderstorms to portions of the region.
The main "dynamics" of this system will be with that wave of low pressure near Columbia, S.C. This low will move northeast along the frontal boundary to a position near the N.C./S.C. border by Sunday afternoon. The strongest dynamics with this system, and the greatest shower and storm threat, will exist along a weak sea-breeze boundary trying to push inland, as well as along the coast in general and particularly so toward northeast North Carolina. I believe this is where the brunt of the shower and storm activity will occur. BUT... while some areas may indeed remain dry, you should keep an umbrella handy for whatever plans you have Saturday.
If you look above at the 500 mb map, just off the map to the right of where I have written "trough," is the center of the Bermuda high pressure ridge, a semi-permanent summer feature which is responsible for heat and humidity. This will work as a "roadblock" on our front, causing it to go nowhere fast and eventually just dissipate Sunday and Monday.
(Again, click or tap on each to enlarge.)
This, of course, means not-so-good news for our eclipse viewing. The NWS office in Columbia, S.C., has a forecast page dedicated to the eclipse and their forecast probabilities. Before I post that, I want to show you what a couple of the weather models are "thinking" in regards to Monday afternoon.
For cloud cover... not looking all that optimistic as far as models go. The GFS tends to be quite overcast while the CMC (Canadian) tends to be a bit more optimistic with less in the way of cloud cover.
With the clouds come shower and thunderstorm chances. Again the GFS is quite bullish in regards to the precipitation coverage than the Canadian. My honest feel is that it will be someplace in between the two.
Again, my opinion is that we'll be somewhere in between. I think there'll be a pretty good skyscape of towering cumulus clouds, but most likely not a full overcast. There may be a scattering of showers and thunderstorms dotting the landscape as well. Pinning down who gets what is impossible at this point... some places will get a great view, and some, unfortunately, will not.
Here is the percentage of cloud cover and percent probability of precipitation from the NWS office in Columbia, S.C.
Unfortunately the only thing I am certain of is that it will be hot.
Ok, wrapping it all up and putting a bow on it, here are your forecast images for southeast N.C. and northeast S.C., including the beach forecast and tides.
Have a great evening. Any questions, comment here or contact me on Facebook at www.facebook.com/CCSkywatch.