textproduct: Columbia

WHAT HAS CHANGED

Updated Key Message #1 and aviation discussion updated for 12Z TAFs.

KEY MESSAGES

- 1. Stratus with patchy fog through mid morning.

- 2. Temperatures continue to be well above normal through at least the mid week next week. - 3. Chances for diurnal showers/storms continue into the early week.

DISCUSSION

KEY MESSAGE #1: Stratus with patchy fog through mid morning. Satellite imagery and observations show mainly stratus across the forecast area with some low end fog near the I-95 corridor. However, a few breaks in the stratus deck are already showing up, which may lead to some other locations seeing brief patchy fog for the next couple of hours.

KEY MESSAGE #2: Temperatures continue to be well above normal through at least the mid week next week.

The strong mid to upper ridge sitting over the region is forecast to remain over the Southeast for the next several days. However, guidance suggests that the trough currently over the Great Plains moves eastward today into Sunday, temporarily flattening the ridge out somewhat. Meanwhile, the southern portion of the aforementioned trough is forecast to become a closed low and drift over Baja California. Eventually, this feature is expected to eject eastward, allowing the ridge over the Southeast to restrengthen. Despite the flattening of the ridge the next couple of days, geopotential heights are still forecast to be anomalously high over the region. Therefore, the temperatures are forecast to remain well above normal. With the ridge restrengthening later in the forecast period, temperatures bump up even higher fore midweek ahead of the next potential trough. Ensemble spreads through midweek remain rather small, leading to a higher confidence in these high temps. The spread increases quite a bit late in the week, leading to more uncertainty.

KEY MESSAGE #3: Chance of diurnal showers into next week.

Although the ridge is forecast to begin flattening some today, the western periphery is expected to stay just to our west. Therefore, the best chances for any showers (and possibly a thunderstorm) this afternoon are in the western portions of the forecast area. The trough mentioned in Key Message #2 is expected to push a front toward the area for Sunday, but it is forecast to become washed out to some extent. That said, there should be enough forcing in the area to produce more coverage of showers and storms than Saturday. The threat for severe weather remains low as the best dynamics are expected to be north of the area. However, a stronger storm cannot be ruled out, especially near the Charlotte metro into the PeeDee region. With the residual heat and moisture, chances for diurnal showers continues into the early part of the week. Due to the lack of a forcing mechanism, coverage is anticipated to be isolated, however. A frontal boundary late in the week could bring higher chances for rainfall to the area.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

VFR conditions have returned to the TAF sites. Another round of stratus is possible tonight, in addition to some showers.

IFR and MVFR stratus from this morning has lifted to VFR cumulus this afternoon as surface heating has commenced. Southerly flow is in place across the area as well, with infrequent gusts of 15-20 knots occurring. Expecting similar conditions through most of the afternoon and evening. Much like yesterday, the setup is such that we may see some isolated to scattered showers especially closer to CAE/CUB this afternoon, but these generally should be weak and short lived. By tonight, these will weaken but a cluster of remnant showers is expected to push towards the region from the west. This is expected to at least persist in some form as it is a pretty solid line of storms ahead of an approaching cold front. I doubt it will be strong enough to cause problems or even make it to OGB as the best forcing should be lifting to our north. The other problem tonight looks like stratus. We will continue to see southerly flow ahead of the approaching front, and with few changes to the setup overall, a persistence forecast seems to make the most sense. So MVFR is forecast at all sites, with IFR expected at OGB, tonight and into early Sunday morning. This has been the case for the past several nights, and that is expected to remain the case. Expect that to lift by mid-morning Sunday, with showers/storms possible again tomorrow afternoon.

EXTENDED AVIATION OUTLOOK...Patchy morning fog remains possible each day. Increased shower and storm chances expected starting Sunday, lasting into next week.

CAE WATCHES/WARNINGS/ADVISORIES

SC...None. GA...None.