textproduct: Columbia

WHAT HAS CHANGED

Aviation Discussion updated for 00z TAF issuance.

KEY MESSAGES

- 1. A Freeze Warning will be in effect late tonight into Sunday morning.

- 2. Below normal temperatures are expected to persist through early next week, moderating by mid next week.

DISCUSSION

Key Message 1: A Freeze Warning will be in effect late tonight into Sunday morning.

We can expect the coldest temperatures of the season tonight and into Sunday morning. Radiational cooling will be much more efficient tonight due to lighter winds and a weakening pressure gradient. Confidence remains high that widespread sub-freezing temperatures will occur early Sunday morning, especially across the northwestern CWA where NBM probabilities for temperatures at or below freezing are near 100 percent. Forecast lows are generally in the lower 30s, but many locations will fall into the mid to upper 20s by daybreak. A Freeze Warning is in effect from 1 AM through 9 AM Sunday.

Key Message 2: Below normal temperatures are expected to persist through early next week, moderating by mid next week.

Broad high pressure will continue to usher a chilly airmass into the region through early next week. Afternoon high temperatures will remain below seasonal averages, generally ranging from the upper 50s to low 60s, while overnight lows will dip into the 30s for multiple nights. Confidence is increasing among global models that upper-level ridging will gradually build overhead by mid to late week, allowing temperatures to moderate closer to seasonal normals. Unfortunately, model guidance continues to show little indication of any meaningful rainfall through the upcoming week, suggesting dry conditions will persist.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

VFR conditions expected through the period with NW winds.

Dry weather and clear skies with VFR conditions will continue through the TAF period at all terminals. Light winds have developing across the region as of 00z, and it should be noted that a northeasterly 15 to 20 kt north- northeasterly low- level jet between 500 and 1500 ft will develop above the nighttime inversion tonight, but this will remain weak enough to not pose low-level wind shear concerns. Light surface winds and clear skies will continue into Sunday morning and afternoon.

EXTENDED AVIATION OUTLOOK...Dry air will likely prevent widespread restrictions through the extended period.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Freeze Warning from 1 AM to 9 AM EST Sunday for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. GA...Freeze Warning from 1 AM to 9 AM EST Sunday for GAZ040-063>065- 077.