textproduct: Columbia

WHAT HAS CHANGED

No major forecast changes. Rainfall amounts remain uncertain for this coming week. Updated aviation discussion for 18z TAF.

KEY MESSAGES

- 1. High pressure and a cooler and drier air mass settles over the area tonight and Monday.

- 2. Showers and t-storms possible mid-week and this weekend

DISCUSSION

Key Message 1: High pressure and a cooler and drier air mass settles over the area tonight and Monday.

The surface boundary that has been sinking southward through the forecast area and sparking some isolated showers is pushing through the CSRA as of 8pm. The loss of heating and instability has resulted in diminished shower activity and dry conditions should continue through the overnight hours. Lower dewpoints already pushing into the northern Midlands with dewpoints in the lower 50s and further drying is expected with increasing northeasterly flow overnight as high pressure builds in.

Key Message 2: Showers and t-storms possible mid-week and this weekend

The synoptic pattern shifts this week as ridging is replaced by upper troughing over the eastern US. This will lead to multiple chances for rainfall first mid-week, then next weekend. NAEFS IVT over the region rises to the 90th percentile of climatology indicating moisture advection into the Southeast and support for at least a chance of showers and thunderstorms. The lower end of QPF probabilities from the NBM have come up slightly with the 25th percentile up to 0.2 inches, however there is still a large spread in rainfall amounts showing the uncertainty. The deterministic NBM also is skewed towards the higher end of QPF with totals through mid-week nearly twice as much as the median. Additionally, moderate wind shear may help some low end storm organization, and these trends are being monitored in the various model guidance for severe weather potential on Wednesday or Thursday.

AVIATION /00Z MONDAY THROUGH FRIDAY/

VFR conditions exist currently but the forecast period becomes a bit more tricky overnight tonight as surface high pressure ridges in from the northeast.

A backdoor front of sorts has passed through the area and is ushering in dry surface air as I type this. Some brief MVFR cigs were noted in the clouds that follow this feature but didn't really materialize at CAE/CUB. What is more interesting is how poorly post guidance is handling the stratus associated deeper into the surface high across NC and Virginia. This stratus is rapidly expanding southeastward, with only the HRRR really initializing its extent well. The HRRR also is showing this shallow layer of moisture pushing southeastward with time & yielding MVFR ceilings at all of our TAF sites later tonight. Expecting this to overspread the region between 04z and 07z, with MVFR cigs expected by 07z-09z at the sites. This is not something shown in all guidance; however, the HRRR has been consistent and is reflecting current observations the best. Therefore, utilizing this for the forecast overnight. Stratus is likely to break sometime late morning or early afternoon, with scattered cumulus likely tomorrow afternoon. Winds throughout the period will likely be out of the northeast between 7 and 12 knots.

EXTENDED AVIATION OUTLOOK... Periodic restrictions will be possible over the next week with a more unsettled pattern and chances for rain continue, mainly Tuesday and into the mid week.

CAE WATCHES/WARNINGS/ADVISORIES

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