textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAF issuance.

KEY MESSAGES

- 1. Daily chances for showers and storms continue through Tuesday, with locally heavy rain possible.

- 2. Relatively cool temps expected today and early this week, followed by a warming trend.

DISCUSSION

Key Message 1: Daily chances for showers and storms continue through Tuesday, with locally heavy rain possible.

The cold front is very slowly shifting into the Pee Dee region as of writing this with surface dewpoints down into mid to upper 50s seen just across the SC/NC border. South of the front, PWAT's remain between 1.7-1.9" with isolated to widely scattered showers and a couple weak storms on going. This activity is exhibiting very slow storm motions and at times, backbuilding, as 0-6km shear vectors are almost perfectly parallel to the front. Minor nuisance flooding in isolated spots cannot be ruled out into the morning hours mainly toward the CSRA and far southeastern Midlands as the front continues to slowly sag southward. The front is expected to nearly stall near/just south of the CSRA where drier air (PWAT's dropping to 1.30- 1.50) behind the front may aid in limiting PoP's, especially east of the I-26 corridor. With the front lingering near the southern FA and multiple weak shortwave impulses moving through the troughing pattern over the eastern CONUS, Slight chance to chance PoP's are expected mainly across the CSRA this afternoon/evening where the threat for locally heavy rainfall and spots of flash flooding will remain as forecast soundings continue to indicate long/skinny CAPE profiles coinciding with PWAT's over 1.75" and warm cloud layer depths that exceed 12,500 to 13,500 ft. A stronger shortwave is expected to move through tonight into Monday, and deeper moisture may return northward as the front becomes increasingly diffuse, increasing shower/storm chances across the FA. Some uncertainty remains in these chances as the greatest moisture convergence may end up just south of the FA.

The diffuse front is expected to meander through the FA Monday and Tuesday with multiple shortwaves working into the region as an Omega blocking pattern remains in place over the CONUS. A more robust cold front is expected to work through the area late Monday into Tuesday and ahead of this stronger front, more scattered shower/storm chances should exist each day as deep moisture remains in place. A push of drier air behind the front along with developing low pressure off the coast should bring dry conditions to the CWA by Wednesday.

Key Message 2: Relatively cool temps expected today and early this week, followed by a warming trend.

There has been little change to the temperature forecast in the coming days. Depending how widespread cloud cover is through the day today, temperatures may trend a bit lower. The latest run of the NBM brings temperatures in the mid to upper 70s across the FA, but some MOS data favors temperatures closer to the low to mid 70s so cloud cover trends will need to continue to be monitored through the day today. After this, temperatures are expected to remain just below normal with continuing rain chances and increased cloud cover through Tuesday. The aforementioned Omega block is expected to begin breaking down by the mid week with the upper ridge positioned over the Plains gradually shifting eastward, before fully moving overhead late in the week. Besides drier conditions under the ridge, temperatures are expected to warm Wednesday onward as shown in recent ensemble and cluster guidance.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Brief IFR ceilings possible this morning, otherwise MVFR ceilings expected through the day with showers possible.

A front is moving through the area early this morning, allowing for scattered showers along it but with some drier air moving in from the northeast with somewhat gusty NE winds, shifting more easterly. This drier air aloft will lead to decreasing rain shower coverage over the next few hours. While mostly MVFR ceilings have been observed a brief period of IFR ceilings remains possible for the AGS/DNL/AIK/OGB. Guidance has been fairly consistent in keeping MVFR ceilings throughout much of the day as the front will stall near the southern forecast area. Confidence remains highest in continued restrictions in the southern terminals closer to the front. With lingering low level moisture and the front in the area, rain showers may redevelop later today into this evening. Ceilings likely lower further into tonight, although uncertainty as to whether they will be low MVFR or IFR.

EXTENDED AVIATION OUTLOOK...Unsettled weather should continue into early next week until drier air moves into the region mid- week.

CAE WATCHES/WARNINGS/ADVISORIES

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