textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAFs.

DISCUSSION

KEY MESSAGE #1: Near record temperatures very likely this afternoon. A bit of a temperature roller coaster is expected after this.

Deep troughing in the west will advance east today, amplifying the upper ridge over the eastern CONUS. This will force 500 mb heights over the region near the NAEFS 97.5 percentile, and consequently 850mb temperatures above to 99.5 percentile to MAX all time. With the NBM MaxT interquartile range of only 2 degrees for CAE (88-90 degs F as of the 0311/01z run), there is very high confidence of near record highs this afternoon. Temperatures are forecast to be between 85-90 degs F across the Midlands and CSRA, and the record highs for both CAE and AGS is an at-risk 88 degs F, set back in 1990.

However, this pattern is expected to shift quickly on Thursday as an upper low tracks across the Deep South before phasing with the northern stream trough. As lower heights move over the area along with increasing cloud cover and precipitation (more on that in Key Message #2), temperatures will moderate 20 degrees or more and be much closer to seasonal normals (generally in the mid to upper 60s for mid March). A bit of a temperature roller coaster is then expected into early next week, with a few days of warmer temperatures this weekend and then more uncertainty toward the end of the forecast period as the potential for some below normal temperatures enters the picture.

KEY MESSAGE #2: A front crossing the region Thursday morning and afternoon will bring gusty winds along with showers and thunderstorms.

Confidence remains moderate to high regarding a decent shot for rain in most areas on Thursday as an airmass-changing front crosses the region. Remaining uncertainty, mainly with timing and any severe potential, stems from how the aforementioned upper low interacts with and is absorbed into the northern stream trough as it tracks across the southeast. What is more clear, is that deep southwesterly flow ahead of the upper low will drive PW values to between 1.25" and 1.5", which is 175%-225% of normal. Dewpoints will remain in the low 60s into Thursday morning as a cold front moves toward the forecast area from the west. Guidance continues to favor the late Wednesday night into Thursday morning period for the timing of the frontal passage which is coincident with the best rain chances. In terms of the timing uncertainty, the longer range models and their ensembles are generally favoring a faster solution, with the short term and near term models slightly slower. A faster evolution would limit the thunderstorm and severe potential, keeping instability limited and favoring areas to the east later in the day. A slower solution would likely favor more thunder due to higher instability present when the front crosses later Thursday afternoon. Therefore, the overall severe threat remains a bit conditional as the finer details continue to come into better focus.

Temperatures on Thursday also deserve a mention, given that now 24- 36 hours out, there remains a 4-8 degree interquartile range for NBM values Thursday afternoon. This spread is even larger in the LREF, with most of the area seeing spreads of 6-10 degrees, and even higher discrepancies for the eastern forecast area to the coast. That said, the temperature forecast confidence is low for Thursday, and will be dependent on the timing of the front, rain, and how fast cold advection commences over the area.

A final note; there is fairly good agreement and high confidence that southwest winds ahead of the front will be gusty, and continue to be elevated behind the front for a time as winds shift to the northwest and eventually north. The pressure gradient looks to be pretty strong, and will be enhanced by 35-45 kt winds at 850 mb. Most guidance indicates the potential for gusts of 20-30 mph, and trends will be monitored for the potential need for a Lake Wind Advisory.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

VFR Conditions Expected Today with Breezy Winds Developing....

VFR conditions continue at all terminals except AGS which continues to deal with variable visibility due to transient river fog. TEMPO has been extended until 13z to account for this. Otherwise, skies are mostly clear to partly cloudy early this morning as mid to high level cloudiness moves in from the west. Light winds at daybreak will increase quickly after daybreak out of the southwest to around 15 knots with gusts up to 25 knots at times in the afternoon. Winds diminish in the evening. Clouds should lower and thicken towards daybreak as a cold front approaches from the west but rain should hold off until after the current TAF period.

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.