textproduct: Columbia

WHAT HAS CHANGED

Area is in a slight risk for severe storms today and tomorrow. Included mesoanalysis for early this afternoon. Aviation discussion updated for 18z.

KEY MESSAGES

- 1. Scattered storms each afternoon through Monday with heavy rain and frequent lightning. Damaging wind gusts possible in strongest storms, especially today and tomorrow.

- 2. Hot and humid this weekend with cooler temperatures next week.

DISCUSSION

Key Message 1: Scattered storms each afternoon through Monday with heavy rain and frequent lightning. Damaging wind gusts possible in strongest storms, especially today and tomorrow.

Active pattern will continue this weekend into early next week. Upper ridging has shifted offshore with a more zonal pattern developing aloft. This has led to subtle shortwaves passing through an unstable air mass with lingering above average heat and humidity continuing through the weekend. Highly unstable air mass has already developed today with RAP analysis indicating sbCAPE is already exceeding 3000 J/kg. With GOES satellite imagery showing a lingering boundary in the NW portion of the area from lingering convection earlier this morning, expect sufficient forcing to lead to scattered storms continuing through this afternoon. While shear remains fairly weak, generally weak to moderate cloud layer flow, the environment does support wet microbursts through the afternoon with low level lapse rates exceeding 8 C/km and TEI above 25C. Damaging wind gusts expected to be the primary threat with a slight risk for severe weather from SPC today.

Tomorrow, an upper low approaches the area with a somewhat similar environment expected with strong destabilization and potential for wet microbursts once again with a slight risk continuing across much of the forecast area. Depending on the evolution of convection over the next 24 to 48 hours, we may need to monitor some spots for potential flash flooding, although storm motion should be sufficient to prevent significant flooding concerns outside of any training.

Monday, a cold front drops towards the forecast area, providing additional forcing for convection, although lingering storms Sunday night into Monday morning may prevent as significant destabilization with cooler temperatures expected. Will need to continue to monitor a potential flash flood threat, keeping in mind this will depend significant on antecedent conditions from Saturday and Sunday. In general, ensemble means have trended much slower with the advancement of dry air into the area next week and conditions may remain unsettled into the middle of next week with ensemble means keeping PWATs greater than 2 inches through Tuesday and with only a somewhat marginal decrease Wednesday into Thursday.

Key Message 2: Hot and humid this weekend with cooler temperatures next week.

Hot and humid conditions expected both today and tomorrow with max temperatures likely reached early afternoon for many locations before the onset of significant convection. Heat indices likely still rising into the triple digits Saturday and Sunday with any decrease in temperatures offset by the increase in dew points. Blended guidance has creeped up slightly in the last several runs on temperatures for Monday and Tuesday as increasing confidence in the front lingering near the area, preventing a significantly cooler air mass from moving in with a decent temperature gradient expected from north to south. Still expect below average temperatures Monday and Tuesday, which feels like a win. This will likely be short lived, however, as the air mass likely recovers for the second half of the week with temperatures near to slightly above average.

AVIATION /18Z SATURDAY THROUGH WEDNESDAY/

VFR conditions are expected to persist outside of thunderstorm activity this afternoon.

We have had an early start to the convection this afternoon. A remnant shortwave is pushing out of the Appalachians and into the coastal plain of the Carolinas this afternoon. Moisture is rich and there is plenty of instability, so we are expecting numerous showers and thunderstorms to continue initiating this afternoon and evening. Area TAF sites will be prone to this but it is uncertain who will get what and when. The result is a prevailing VCTS this afternoon with a PROB30 for impactful storms. May need a tempo group (or a brief prevailing group) if storms are expected to directly impact a site. Gusts of 30-40 knots (or higher) are possible with convection today as well as visibility restrictions between 1sm and 2sm. Convection will likely wane between 22z and 02z this evening as we expect the atmosphere to be pretty well worked over by that point. Light winds and convective cloud debris will remain through the night, with ceilings likely between 15kft and 20kft through the night. Another round of strong thunderstorms is expected on Sunday afternoon (likely just after this period ends), with widespread cumulus again developing by 15z Sunday.

EXTENDED AVIATION OUTLOOK...Increasing chances for afternoon storms Sunday and into early next week.

CAE WATCHES/WARNINGS/ADVISORIES

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