Charleston Weather Blog

Forecast explanations, atmospheric science, and other cool weather-related stuff for Charleston, SC

Friday & the (holiday) weekend: Unsettled start tapers off a little bit around the Fourth

/ June 30, 2022 at 10:27 PM

After some of us got a day to dry out, showers and thunderstorms look to resume possibly as early as late tonight as a disturbance aloft possibly spawns a little surface low in southeast Georgia. This possible low, if not the associated surface trough, will help to keep numerous showers and thunderstorms in the forecast for Friday and into Saturday as well. We could see storms ongoing Friday morning for the commute, so be ready to take it a little slower on the roads. Heavy rain and lightning will be the primary issues from any thunderstorms. The atmosphere remains juiced with plenty of moisture: precipitable water values (the amount of water you can wring out from a column of air) will continue to run very close to 2″. This moisture combined with ample instability will likely lead to some pockets of very heavy rain rates and a risk of minor flooding to go along with it. Also, it’s worth noting that high tide will peak around 10:17 AM in Charleston Harbor. Guidance does show some heavy downpours coming ashore ahead of and around this time, which could enhance the flood threat in coastal communities including downtown Charleston. With the prevalent storms and cloud cover, highs should top out in the mid-80s at best. It’ll be quite humid, though, and so heat indices could run up toward 90° especially if some sun peeks out.

Saturday looks like it could get off to a similar start as broad surface low pressure may be moving through the area during the morning. Additional showers and thunderstorms could then fire in the afternoon in the wake of the low depending on how well the seabreeze ultimately develops. Temperatures should stay capped in the mid-80s once again, owing to the unsettled weather that’s expected. Something tells me the details around Saturday will be refined some more, too, so stay tuned.

Sunday will be a little more summer-like in nature with more widely scattered thunderstorms, particularly in the afternoon. Temperatures will rebound from previous days into the mid-to-upper 80s.

Independence day forecast

After record rainfall, more storms to come Thursday

/ June 29, 2022 at 9:58 PM

After record rainfall today — 1.87″ of rain at the airport breaks the record of 1.54″ set in 2000, while stations in West Ashley picked up 2.5-3″ — more storms are on the horizon for the next few days as we remain within a very humid airmass with plenty of upper-air and surface features to help spur on shower and thunderstorm development.

Thursday looks to go similarly to the past couple days, though there may not be quite as much coverage as we’ve seen thus far this week. We could see showers and storms forming early in the day near the coast, with storms becoming scattered to numerous while translating inland with the seabreeze throughout the afternoon. With precipitable water values near 2″, we once again could see pockets of very heavy rainfall. The past couple days have seen a couple 4″ bullseyes, and I can imagine that will be the case somewhere again tomorrow. The severe weather risk remains very low given the very saturated atmosphere, but lightning and isolated bouts of excessive rainfall will make any thunderstorm dangerous. High temperatures will remain suppressed in the mid-80s, though the humidity will still be rather swampy.

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Rest of the work week remains unsettled with some much-needed rain

/ June 28, 2022 at 9:22 PM

After some much-needed rain fell across the area — with upwards of 2-4” in many spots near the coast, particularly around Mt. Pleasant — more is in store overnight tonight into Wednesday as a stalled front continues to linger in the area. Mid-level energy will traverse the area and should initiate another round of showers and thunderstorms overnight into tomorrow morning. We’ll want to keep an eye on the risk for waterspouts again in the morning, too, though whether it’s a repeat of today’s performance remains to be seen.

The front will eventually wash out later Wednesday, but we’ll still have plenty of moisture in the area and surface triggers in the form of a coastal trough and other mesoscale boundaries to help maintain solid rain chances Thursday and Friday.

The rain will continue to keep high temperatures suppressed into the mid-80s each afternoon. Thunderstorms will certainly act as a temperature disruptor, and as a result, the timing for places to reach those highs — if they’re reached at all! — could vary widely across the Tri-County.

Moisture looks to hang around for the holiday weekend, and it’s increasingly likely we’ll at least be dodging some afternoon thunderstorms for the Fourth of July. Will continue to keep an eye on this as we get closer, but for now, the advice is to make sure you’ve got a good second, indoor option for your Independence Day festivities.

Tuesday: Shower and thunderstorm chances return

/ June 27, 2022 at 10:16 PM

Showers and thunderstorms return to the forecast on Tuesday as a front sinks into the area and stalls out. A good bit of you should see at least some rain tomorrow and over the next few days as the stalled front continues to hang around with plenty of available moisture. Given the time of year, of course, not everyone will see the same amount of rain — some of you could see very little, while others may be crying “Uncle!” by the time the week is over. It all ultimately depends on small mesoscale accidents that are impossible to predict with more than an hour or two of lead time. On average, a half-inch to an inch of rain in spots through the end of the week looks pretty reasonable.

Showers and storms will keep us out of the 90s for the foreseeable future, too. Tuesday will run in the upper 80s, but we should see temperatures suppressed solidly in the mid-80s for the rest of the week with the ongoing unsettled pattern. It looks like we’ll keep elevated storm chances into the holiday weekend, too, so be thinking about a backup plan for your outdoor activities to celebrate the Fourth.

The week ahead: Rain chances return

/ June 26, 2022 at 9:40 PM

At Sunday dinner tonight, my mom remarked to me that her grass was getting awfully crunchy with the lack of rain. Fear not, Mom and others: Rain chances return to the forecast starting Tuesday and will continue for the next several days as a front presses into the area and stalls out. We could see some fairly heavy downpours at times as precipitable water values — essentially, the amount of water you could wring out of a column of air — approach 2″ across the area heading into Tuesday and Wednesday. The caveat, as always, is that it won’t rain all the time at any one location, and some locations will see more rain than others. (A few spots might even get shut out. Such is life in late June.) Once the front washes out and high pressure rebuilds heading toward the weekend, storms will be more scattered in nature, driven by typical daytime heating and forcing along the seabreeze. Overall, most spots can expect generally about 3/4″ of rain on average during the week with locally heavier amounts. It’s not going to bust the drought, but it should at least blunt it a little.

Cloud cover and thunderstorms will also help to keep temperatures down; below-normal temperatures are forecast for a good chunk of the week, in fact, with heat indices not really factoring in all that much especially on Tuesday and Wednesday. Monday will act as the high-mercury mark for the week, starting us in the low 90s before the front approaches and temperatures generally top out in the mid-to-upper 80s for the rest of the week. We could see another run at 90° for Sunday as the aforementioned high pressure settles back in, but all in all, welcoming July without oppressive heat and some beneficial rain isn’t all bad.

Temperatures near normal with less humidity this weekend

/ June 24, 2022 at 8:34 PM

While not quite as dry as we saw this past weekend, humidity will certainly not be stifling this weekend with east and northeast flow keeping cooler and drier air in place. After a nice start to Saturday morning, expect highs to top out just shy of 90° (even cooler closer to the coast). Thanks to the lower dewpoints, heat indices will not run too far out of bounds — probably topping out around 92°. Sunday will bring similar conditions with even more in the way of sunshine. Our next rain chance will be Tuesday, with chances heading up as we head further into the next work week. That being said, we have plenty of time later to think about the next work week — let’s enjoy the weekend first.

Friday & the weekend: Temps slack off a little, humidity a little lower this weekend

/ June 23, 2022 at 6:27 PM

A front will sag southward across the area on Friday, bringing with it some cooler temperatures and a slight chance of afternoon thunderstorms. We’ll lop about 6-8° off today’s observed high of 96° tomorrow as winds turn a little more onshore as the front gets by. Only a few of us will see storms tomorrow, so keep the watering gear on standby as you’ll probably need it for a few more days.

Ridging aloft will continue to build into the area for the weekend, but east to northeast winds at the surface will help keep temperatures and humidity (to an extent) in check. Expect highs in the upper 80s to around 90° each afternoon with dewpoints running in the upper 60s, yielding heat indices in the low 90s. Mostly sunny skies will be the rule with the somewhat drier atmosphere and sinking air keeping updrafts in check. While the air won’t feel quite as nice as last weekend, it’ll still be a good couple beach days. Pack the sunscreen!

One more hot day Thursday before temperatures return to normal for the weekend

/ June 22, 2022 at 8:13 PM

Thursday will be the hottest day this week as air temperatures return to the mid-to-upper 90s across the Lowcountry in the afternoon. Unfortunately, dewpoints will also have recovered back into the 70s, and that could put us close to heat advisory territory for Thursday afternoon as heat indices could approach 105°. There will, however, be a shot at some isolated thunderstorms later in the afternoon into the evening hours as the seabreeze makes its move inland. Lightning and gusty winds will be the primary concern from any thunderstorm that forms, but so far widespread severe weather doesn’t look likely.

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Rest of the work week: Peak warmth as we reach the hump; storm chances return

/ June 21, 2022 at 9:57 PM

After today came in cooler than expected thanks to some cloud cover (and even a few light showers), the heat should begin to really kick back in on Wednesday as we’ll see much more sunshine than we did today. The atmosphere remains dry and capped, and that will keep afternoon shower and thunderstorm chances at bay for one more day. 70s dewpoints return in earnest for Thursday, and that combined with a 97° air temperature will drive heat indices into the lower 100s in the afternoon. We’ll also start to see the standard slight chance of afternoon thunderstorms return to the forecast Thursday. A weak front will head south across the area late Thursday into Friday, taking the edge off the higher heat for Friday with highs topping out around 90°. We’ll keep a slight chance of seabreeze storms in the forecast to close out the week.

Tuesday: A little bit warmer, still not intolerably humid

/ June 20, 2022 at 6:04 PM

Tuesday will be another warm day with plenty of sunshine and still-tolerable humidity. Highs will continue their warming trend, with low-to-mid 90s possible in the afternoon hours. Dewpoints in the low 60s, though, will yield relative humidity values around 35-40% at the peak of the day. This could make the heat index feel slightly cooler than the air temperature, which is a welcome anomaly for this point in the year. Much like the past few days, the drier air will help suppress afternoon shower and thunderstorm chances.

The warmest day this week looks to be Wednesday, as highs top out in the upper 90s away from the coast (though, thankfully, we’ll still benefit from some drier-than-normal air to keep heat indices somewhat in check). Wednesday could challenge the record high (98° in 2015 and 2011) so we’ll want to keep an eye on that. Dewpoints return to the 70s on Thursday, and heat indices will respond by heading into the low 100s. We’ll also start to see some slight afternoon shower and storm chances creep back into the forecast, too. Temperatures moderate a little on Friday with a little more onshore flow but also a small uptick in shower and thunderstorm chances as well.