textproduct: Columbia

WHAT HAS CHANGED

Air quality alert has been issued for Lancaster county for Friday. Aviation updated for 00z TAF.

KEY MESSAGES

- 1. Generally low chances of rain through Friday, favoring the CSRA with a warming trend expected across the area.

- 2. Increased chances of rain and severe weather over the weekend with highest chances Sunday into Monday.

DISCUSSION

Key Message 1: Generally low chances of rain through Friday, favoring the CSRA with a warming trend expected across the area.

The last few lingering showers are now diminishing across the FA with dry conditions expected to persist overnight into Friday morning. Isolated convection will be possible again Friday afternoon/early evening. The only change at this hour looking ahead is the South Carolina Department of Environmental Services has issued an Air Quality Alert for Lancaster County due to increased ground level ozone concentrations that could be unhealthy for sensitive groups. This will be in effect from 10AM to 8PM Friday.

Little change for the remainder of the work week with temperatures warming further Friday as broad upper ridging spans the entire CONUS. NAEFS continues to show 850mb temperatures above the 99th percentile both days while even remaining above the 90th percentile through the middle of next week. 700mb temperatures are also above the 97th percentile into the middle of next week. Notably, the bullseye of highest anomalies is generally toward the coastline and eastern NC, so perhaps expect the eastern Midlands into the Pee Dee reach the hottest temperatures during this stretch. From a sensible weather perspective, expect high temperatures to push back into the mid and upper 90s with Friday being the warmest day. Dewpoints were adjusted down for both today and Friday to account for some deeper mixing which would result in some drier air mixing down to the surface as the NBM continues to remain slightly too moist. Still, these values will be in the low to mid 70s and heat indices are expected to rise back above 100 degrees and could reach 105 or higher by Friday, but not quite high enough to warrant a heat advisory at this time.

Key Message 2: Increased chances of rain and severe weather over the weekend with highest chances Sunday into Monday.

A broad trough will dig across much of the eastern US over the weekend, dragging a diffuse trough down through our region Saturday and Sunday. Surface convergence, along with a possible weak tropical disturbance, will yield very PWAT's over 2.25" and in conjunction with height falls as the trough approaches, moderate instability across our area. Saturday appears to be a more typical enhanced pulse thunderstorm day, with only modest mid- level support as notable shear remains north but thermodynamics are primed. Sunday, as the surface trough approaches, and the mid-level trough brings some notable cloud layer shear around 30-35 knots, could bring more organized clusters and a further enhancement to severe potential; a slight risk for severe (2 out of 5) is out for the I-77 corridor into the Midlands. The wildcard in all this is the potential weak tropical disturbance that may develop along the stalled surface boundary, either in the northern gulf or in the coastal Atlantic. While it will very likely not bring any significant impacts in its own right, it will plausibly enhance both moisture convergence and kinematics for our area, boosting any severe or flash flood threat both Sunday and again on Monday. Model guidance across the board is struggling with how to place and shift this diffuse low center, so it may take another few runs to better identify any potential impacts it may bring.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

Generally VFR conditions expected through the TAF period.

Scattered diurnal convection continues to wane this evening with scattered to broken high clouds mainly over the CSRA. Winds expected to be light overnight from the south and clouds should gradually thin through the night. There is a possibility of brief morning fog especially if skies clear out fully so included a tempo group from 11z-13z for MVFR vsbys. Isolated convection possible again Friday afternoon.

EXTENDED AVIATION OUTLOOK...Potential for restrictions from showers and thunderstorms return this weekend.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Air Quality Alert from 10 AM to 8 PM EDT Friday for SCZ115-116. GA...None.