textproduct: Columbia

WHAT HAS CHANGED

A few lingering showers diminishing early this morning.

KEY MESSAGES

- 1. Daily shower and thunderstorm chances continue through the week, with isolated flash flooding possible again today.

DISCUSSION

Key Message 1: Daily shower and thunderstorm chances continue through the week, with isolated flash flooding possible again today.

The overall pattern remains generally the same for one more day as the offshore ridge and and a digging trough in the western CONUS keeps southwest flow over the region. This will keep moisture levels very high with PWATs around the 2", which is about 150% of normal for this time of year. Weak shortwave energy is forecast to move through the area again today, bringing chances for more showers and thunderstorms through the day, mainly in the afternoon and evening, but the overall coverage is anticipated to be less than Monday. With the abundant moisture in place, localized heavy rain is possible once again. The 00z HREF LPMM guidance is showing a couple of pockets of 4" or more of rain possible this afternoon, which is a reasonable high end scenario for rainfall given the state of the atmosphere. Should this occur, especially if it falls on an area that has seen higher amounts of rain through the weekend, flash flooding would be possible. After today a trough is expected to dig from Canada down the eastern seaboard, aiding in slowly pushing the highest PWATs southward. As a result of this as well as a lack of forcing, precipitation chances decrease for tomorrow and Thursday. The trough is then forecast to push a front through late this week into the weekend, possibly bringing drier air into the region behind it. There is uncertainty in this as guidance is not in great agreement for late in the forecast period.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Overnight ceiling restrictions and patchy fog expected. Scattered thunderstorms may impact the terminals with highest chances in the afternoon.

A few lingering showers early this morning will continue to diminish so impacts to the terminals are not expected. Abundant low level moisture has contributed to ceiling restrictions at all TAF sites, except OGB, this morning. LIFR or IFR restrictions will persist for a few more hours then begin to improve.

Ceilings will improve through the morning with sites possibly returning to VFR by 15Z but could stay MVFR into the afternoon. Scattered showers and storms are expected again today. The greatest convective coverage is expected after 18Z but isolated showers are possible prior to that. Outside of thunderstorms, surface winds will be less than 10 kts out of the south or southeast. With some clearing expected in the evening we could see low stratus and fog develop due to abundant low level moisture across the region. Forecast wind profiles and the HRRR tend to favor stratus over fog. At least periodic restrictions are expected once again tonight with IFR or lower ceilings possible. A persistence forecast was favored with restrictions similar to the previous night expected.

EXTENDED AVIATION OUTLOOK...Morning fog/stratus possible each day this week. Scattered, diurnally driven convection expected through Friday.

CAE WATCHES/WARNINGS/ADVISORIES

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