textproduct: Columbia

WHAT HAS CHANGED

Updated Aviation Discussion

KEY MESSAGES

- 1. Confidence remains high in significant warming trend into the weekend, possibly continuing into Monday before a weak front moves in.

- 2. Slight chance for isolated showers and storms Saturday afternoon/evening.

DISCUSSION

KEY MESSAGE 1: Confidence remains high in significant warming trend into the weekend, possibly continuing into Monday before a weak front moves in.

The robust 3-4 standard deviations above normal ridge remains anchored near the Four Corners region as troughing pushes off the Eastern seaboard. As the upper ridge slowly expands eastward, 500 mb height rises on the order of 3-4dm/12hr are expected to move into the region today with warming 850mb temps toward 10C as low level flow becomes more southwesterly. This set up will allow temperatures to rise into the 70s this afternoon, before 850mb temps reach toward the NAEFS 90th percentile Saturday, and the 99th percentile Sunday and Monday as mid level height rises generally continue. Temperatures Saturday are expected to reach into the low to mid 80s before warming a bit further Sunday and Monday, where temperatures could be nearly 15 degrees above normal. Confidence has increased in this warming trend continuing into Monday as global and ensemble guidance continues to slow the arrival of a weak surface front until later Monday evening and into Tuesday. This is seen in NBM IQR ranges for temperatures that are now less than 4 degrees Monday afternoon. These warmer than normal conditions are highlighted well in the EC EFI with values between 0.70-0.90 seen Saturday through Monday before temperatures are expected to cool some on Tuesday behind the weak front.

KEY MESSAGE 2: Slight chance for isolated showers and storms Saturday afternoon/evening.

There has been a slight shift in guidance toward favoring the potential for isolated showers and storms Saturday afternoon and evening. There is greater agreement that a weakening shortwave will round the ridge toward the Northern Plains, working southeastward into the FA by Saturday evening. There also is a signal that a fairly washed out front could approach the Pee Dee as well. With this shortwave impinging on the region, enhanced mid level flow aids in generating increased moisture transport with PWAT's topping out near 1.25". Greater surface convergence is also evident across the FA as the diffuse front nears the Pee Dee, thus recent CAM solutions and the 00z HREF indicate potential for the development of showers and some storms. Instability is not all that impressive all things considered with MLCAPE generally under 1000 J/kg (though the latest HRW- NSSL is closer to 1500 J/kg) and the weak shortwave, while bringing sufficient forcing for initiation, does not bring impressive dynamics with it as deep layer shear is generally under 30 kts. This goes to say, there looks to be sufficient forcing and instability Saturday afternoon/evening for showers and storms, but coverage is looking to be limited. A strong inverted v in the boundary layer does yield 700-900 J/kg of DCAPE so the strongest storms could produce sub-severe wind gusts, but the overall severe threat appears quite limited.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Mainly VFR conditions today and tonight.

A bit of ground fog has developed at OGB this morning despite the relatively dry air in place. The ground fog should dissipate quickly after sunrise. Otherwise, light winds will become southwesterly at less than 10 knots as the surface high sags a bit southward. Any clouds over the next 24 hours should be of the thin cirrus variety and not cause any impacts at the terminals. If winds decouple late tonight at OGB or AGS, there might be some patchy ground fog again, but there will be light southwest winds that should keep most places mixed enough to avoid that problem.

EXTENDED AVIATION OUTLOOK... On Saturday, a slight increase in moisture combined with a weak upper level disturbance will cause a few more clouds in the afternoon, with possibly an isolated showers or thunderstorm, but chances remain low for any impact at the terminals. A more significant cold front will move through on Monday, with a slightly better chance for restrictions. Overall, conditions will be most likely VFR for the next several days.

CAE WATCHES/WARNINGS/ADVISORIES

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