textproduct: Columbia

WHAT HAS CHANGED

12Z aviation update.

KEY MESSAGES

- 1. Above normal temperatures likely through Thursday; some uncertainty in temperatures this weekend.

- 2. Rain chances increase late week onward.

DISCUSSION

Key Message 1: Above normal temperatures likely through Thursday; some uncertainty in temperatures this weekend.

Strong upper ridge expected to persist over the eastern CONUS into the upcoming weekend. This will generally bring above normal temperatures to the forecast area over the next several days, however heat indices are expected to remain well below any headline criteria. With that in mind, there is some uncertainty regarding temperatures particularly Friday and Saturday, as there remains some potential for weak cold air damming over mainly the northern half of the forecast area. The latest round of model guidance continues to depict some ridging of surface high pressure south along the eastern Appalachians with strengthening southwest flow aloft. Depending on the strength of this wedge, it is possible that temperatures will be several degrees cooler than blended guidance currently advertises. Temperatures on Friday were therefore adjusted a few degrees cooler, especially impacting the northern portion of the forecast area. It remains to be seen whether these conditions will linger for several days or not, but the blocking pattern in place does indicate the potential is there. It was also noted that the NBM and LREF interquartile ranges for high temps Friday into early next week are 5-8 degrees F depending on the model, further supporting lower confidence in the high temperature forecast over the holiday weekend.

Key Message 2: Rain chances increase late week onward.

Dry conditions persist today with the ridge overhead and high pressure offshore. Expect just some fair weather cu with the peak heating of the day. The upper low offshore under the ridge has created a blocking pattern which is keeping conditions stagnant. There looks to be a slight shift eastward of the large scale pattern in the coming days, with the potential for weak CAD conditions to develop. IVT will be increasing across the Deep South into the TN valley, however it still looks like the best moisture will remain to our west, though potentially as close as the Upstate. Even so, persistent southwest flow aloft and the potential for some overrunning should lead to increased moisture over the Southeast from Thursday through Memorial Day. There remains discrepancies between the ECENS and NAEFS forecast PWAT values, with the EC generally showing better moisture for our forecast area. Initially, it appears the best chance of rain will be Friday into Saturday when the wedge develops. Additional periods of increased rain potential are then expected into early next week, as a few shortwaves move through the larger scale flow and provide additional upper support. It still appears QPFs should be fairly modest given limited moisture transport and the overall upper ridge still in place. NBM probabilities of greater than 0.5" through 00Z Monday range from 80% west of the I-20 corridor to about 60% near the I-95 corridor. These values then drop to 65% and 35% respectively when looking at potential of greater than 1".

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Predominantly VFR with brief morning restrictions.

A very similar synoptic pattern is in place with high pressure offshore and southerly flow leading to continued lingering low level moisture in place. As a result, with models generally supportive of brief restrictions during the early morning period and which favors a persistence forecast. Any low clouds or fog is expected to dissipate shortly after sunrise with southerly winds around 5 knots and a few cumulus around 6kft. An isolated shower could pop up this afternoon but impacts to terminals are unlikely.

EXTENDED AVIATION OUTLOOK...Increased moisture may result in brief restrictions at the terminals due to low clouds and/or fog each day this week. Rain chances increase tomorrow and into this weekend.

CAE WATCHES/WARNINGS/ADVISORIES

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