textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 00z TAF.

KEY MESSAGES

- 1) Above normal temperatures continue through Friday with breezy winds on Friday.

- 2) A cold front brings a chance of rain on Friday. Showers and thunderstorms expected Saturday into Saturday night with improving conditions Sunday morning.

- 3) Cold and dry conditions develop early next week.

DISCUSSION

KEY MESSAGE #1: Above normal temperatures continue through Friday with breezy winds on Friday.

With anomalously warm 850mb temperatures and continued southwesterly flow, another very warm day is anticipated on Friday though clouds and rain should limit how high temperatures get. The pressure gradient increases on Friday ahead of an approaching cold front resulting in with stronger winds that may require a Lake Wind Advisory due to the potential for gusts of 25 to 30 mph. Will defer the issuance of any products to the next forecast cycle to see what the 00Z guidance shows.

KEY MESSAGE #2: A cold front brings a chance of rain on Friday. Showers and thunderstorms expected Saturday into Saturday night with improving conditions Sunday morning.

Guidance continues to support a period of unsettled weather this weekend. The first chance of rain is expected along a passing cold front on Friday. Rain chances increase towards daybreak with a line of showers expected to move through the region during the daytime hours. Rainfall amounts are expected to be light and not every location will see measurable precipitation tomorrow with Chance PoPs in the forecast across the FA. Rain chances decrease Friday night and rise again towards daybreak Saturday.

The weakening bounday is expected to stall near or over the forecast area, possibility moving back north as a warm front on Saturday. The position of this boundary will dictate both temperatures and the highest rain and thunderstorm chances. Confidence in measurable precipitation on Saturday continues to rise and periods of rain are now likely for the entire CWA on Saturday, tapering off Saturday night into Sunday morning. In regards to the thunderstorm risk, the Day 3 SPC Severe Thunderstorm Outlook places much of the CWA in a Marginal (1/5) risk for severe weather. As mentioned, the greatest thunderstorm chances will be along and south of where the frontal boundary sets up but in general the farther south in the FA you are, the greater the thunderstorm chances. Still not overly enthused about the potential for severe weather on Saturday but if we see a setup similar to what is being advertised on the 12Z NAMNest, where the front lifts north and another cold front sweeps in from the west, then there could be a window for isolated severe weather therefore the potential is worth monitoring, especially for the southern Midlands and CSRA.

Much of the weather should be out of the FA by daybreak Sunday but there could be lingering rain across the eastern half of the CWA. Expect improving conditions from west to east on Sunday as the storm system moves northeast. A tight pressure gradient will likely produce breezy conditions as a dry and colder air mass rushes in behind the departing cyclone.

KEY MESSAGE #3: Cold and dry conditions develop early next week.

A potent upper trough is expected to dominate the weather across the Eastern CONUS early next week. At the surface, a cold and dry air mass will move in behind the departing weekend system with below normal temperatures favored. Monday looks to be the coldest day of the next seven followed by a gradual warm up towards the middle of next week. Monday may also be breezy due to a tight pressure gradient but winds should be lighter Tuesday and Wednesday as surface high pressure moves in from the west.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

VFR conditions early tonight, then restrictions down into MVFR possible for a good portion of Friday.

Skies have cleared out for the most part this evening, but with increasing low-level moisture, a return of some stratus is expected towards Friday morning. Guidance continues to show mainly mvfr ceilings developing between 09-12z, with those conditions holding on longer through the morning across ags/dnl. By noontime, most sites should see ceilings improve back to vfr, but with some showers expected to be entering the region around that same time, mvfr restrictions due to visibilities in heavier showers could occur. Much of this activity will be pushing east towards the end of the taf period, with improving ceilings and visibilities back to vfr expected after 20-21z at all sites. Another issue through the period is going to be the sustained winds, and expected wind gusts. A strong low-level jet sets up overnight, and some soundings show a low-level profile that would allow for increasing wind gusts late tonight. Overnight winds will pick back up to around 10 knots, and wind gusts increase back to between 15-20 knots. Even stronger winds expected through the day on Friday with better mixing. Gusts between 20-25 knots possible, and can not rule out a few gusts to 30 knots mixing down as the showers move through during the early afternoon.

EXTENDED AVIATION OUTLOOK...Abundant low level moisture will bring chances for morning fog/stratus into this weekend. Chances of rain continue on Saturday with some thunderstorms possible.

CAE WATCHES/WARNINGS/ADVISORIES

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