textproduct: Columbia

WHAT HAS CHANGED

No significant changes made to key message. Updated aviation for 18z TAF issuance.

KEY MESSAGES

- 1. Seasonal temperatures with increasing thunderstorm chances as the week goes on.

DISCUSSION

KEY MESSAGE 1: Seasonal temperatures with increasing thunderstorm chances as the week goes on.

A weak frontal boundary remains stalled across the Midlands this afternoon and serves as the dividing line between mainly clear skies and fair weather cumulus on midday satellite imagery. This boundary is also evident in the dewpoint gradient, with values in the mid-70s to the south/east and mid-60s to the north/west. For the rest of today and into Tuesday, the upper- level pattern will support northwest flow and continued advection of direr air into the region. As a result, rain chances will remain low, with only isolated diurnally driven thunderstorms possible, mostly along and east of the I-95 corridor. Thermodynamic profiles are expected to remain unfavorable for deep convection, with only shallow, fair weather cumulus in the afternoon outside of the southeastern Midlands. Temperatures will remain near normal, although still relatively warm as highs reach the lower 90s. Lower dewpoints should also keep heat indices from becoming overly oppressive compared to recent weeks.

Moisture will gradually increase from mid to late week, leading to increasing afternoon thunderstorm coverage. LREF probabilities indicate a 50-70 percent chance of PWAT values exceeding 1.75 inches beginning Wednesday. This increase in moisture, combined with upper-level troughing should support greater chances for diurnal convection. Weak shortwaves embedded within the flow may provide additional forcing and further enhance coverage. Thursday currently appears to have the greatest potential for precipitation as the stalled boundary may become reactivated into the FA. However, there remains uncertainty in the evolution and placement of the front. At this time, a significant airmass change appears unlikely, with seasonably warm and humid conditions expected to persist through the period with daily convection chances.

AVIATION /18Z MONDAY THROUGH SATURDAY/

VFR conditions are expected to continue through the TAF period.

A stalled surface front is seen across the far southeastern Midlands, near OGB, with meaningful moisture being kept south of this front, and drier air seen over the remainder of the FA. This is bringing FEW low-topped cumulus as westerly to northwesterly winds around 7-10 kts develop. Any convection this afternoon should be south of the front in the Coastal Plain. Cannot rule out a stray storm near OGB, but probabilities are under 30%. Tonight, dry conditions and light winds are expected with passing cirrus. Latest HRRR/HREF guidance indicates some low-level moisture could pool near the front, bringing patches of fog, but confidence in impacts mainly at OGB are too low to add into the TAF at the moment. After 14-16z Tuesday, winds pick back up around 5 kts, now out of the northeast with VFR conditions continuing.

EXTENDED AVIATION OUTLOOK...Isolated storms each afternoon with higher coverage of storms expected by midweek.

CAE WATCHES/WARNINGS/ADVISORIES

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