textproduct: Columbia

WHAT HAS CHANGED

Slightly better agreement is seen in the timing of Thursday's system. Confidence in near record temperatures tomorrow is very high. Aviation discussion updated for 18z TAFs.

DISCUSSION

KEY MESSAGE #1: Well above normal temperatures this afternoon with near record temperatures tomorrow. A bit of a temperature roller coaster is expected after this.

Temperatures this afternoon are topping out in the low to mid 80s across the area as the apex of the robust upper ridge is nearing the AL/GA border. As the Baja low slowly drifts further east, the ridge will continue to amplify, leading to 500mb heights over the FA near the NAEFS 97.5 percentile with 850mb temperatures reaching near to above the 99.5 percentile. This anomalous airmass brings a very impressive EC EFI signal for max temperatures tomorrow afternoon as values are between 0.99-1 with a SOT of 2 over the FA, highlighting the uniqueness of this set up with near to above record temperatures likely. Temperatures are forecast to be between 85-89F with a spot or two breaking 90F not completely out of the realm of possibilities. The record max temperature for both CAE and AGS is 88F, set back in the 1990. The Baja low is expected to gradually phase with a northern stream trough into Thursday, bringing the next system and front through the area, likely keeping temperatures closer to normal or slightly above normal. After this, a roller coaster of temperatures is expected as cooler/drier air brings near normal temperatures Friday before raising to above normal Saturday and Sunday. Decent uncertainty exists into the early week, but potential for colder than normal conditions is highlighted in blended guidance.

KEY MESSAGE #2: The next system moves in Thursday morning and afternoon with showers and storms possible along with breezy winds.

As short-range guidance begins to reach Thursday, slightly better agreement is being seen in the timing of the incoming system. The main uncertainty still stems from the phasing of the Baja low with a northern stream trough, which should start occurring Wednesday and into Thursday. In general, a later trend with upper support and the surface cold front continues where the main window for showers/storms seems to come after 12-15z and into the early afternoon, though there is some guidance like the recent RAP that trends even later that this. What does seem probable is that a line of showers and possibly thunderstorms should move through the FA with the front as fairly strong southwesterly low level moisture advection develops ahead of the front with PWAT's nearing 1.25". In terms of any potential severe weather with this line, timing differences bring lower confidence in this and the overall environment is fairly borderline. Instability is forecast to be rather meager across guidance with MUCAPE generally under 500-700 J/kg and mid level lapse rates are not that impressive. Deep layer shear though is fairly impressive with 0-6km shear near 55-65 kts, so this would be a fairly typical high shear/low CAPE environment. At this time though, the overall severe threat appears a bit conditional due to the timing differences that still exist, but higher confidence in this outlook should come as more high-res guidance reaches Thursday morning/afternoon.

This front should also bring breezy winds out of the southwest ahead of it before shifting toward the north Thursday evening. This comes as a 30-35 kt LLJ sets up with a tightening surface pressure gradient, leading to gusts up to 20-30 mph.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR conditions generally expected through the forecast period.

A weak disturbance passing aloft could trigger an isolated shower or thunderstorm this afternoon, but the HREF members tend to favor areas just north of the terminals so did not include mention in the TAFs at this time. Otherwise, westerly winds around 10 kt are expected through the afternoon, becoming more light/variable with the loss of daytime heating this evening and persisting through the overnight hours. Winds will increase from the southwest by mid- morning Wednesday. Mid and high level cloudiness is expected through the period, generally scattered in coverage, but some broken clouds are certainly possible at times late tonight into Wednesday morning, but remaining VFR.

EXTENDED AVIATION OUTLOOK...The next chance of significant rain is expected Thursday with a cold front. Gusty winds and some flight restrictions will be possible.

CAE WATCHES/WARNINGS/ADVISORIES

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