textproduct: Columbia

SYNOPSIS

A cold front will move into the Southeast tonight into Sunday ushering in an arctic air mass for Sunday night into early next week. Weak ridging should then allow for air mass recovery by the middle of next week.

NEAR TERM /THROUGH TONIGHT/

Key message(s):

- Warmer weather today, a few light showers possible tonight

An upper level trough will dig into the eastern US driving a cold front into the Southeast overnight. Ahead of the front, SW flow strengthens over the forecast area today leading to the warmest temperatures of December to date. Expect highs in the low to mid 60s. As the front approaches the area late tonight we may see a few isolated showers develop. However, shallow moisture with minimal instability will mean that any rainfall amounts would be light. The few showers may produce localized amounts around one tenth of an inch based on LPMM data from the HREF. The arctic air mass will stay to the north and west of the forecast area tonight so lows will only drop into the 40s.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Key message(s):

- Arctic cold front brings gusty winds and a bitter cold air mass to the area.

- Extreme Cold Watch in effect Sunday evening through Monday morning.

Sunday morning a cold front will be moving through the area. HREF mean indicates that PWATs in the eastern portion of the area, near I- 95, will be above an inch with drier air continuing to push in from the northwest through the day. Majority of HREF members have at least isolated showers in the east through the morning with total rainfall expected to be limited (10 percent or less chance of greater than a tenth of an inch after daybreak). High temperatures will likely be reached in the morning with strong cold advection leading to falling temperatures during the afternoon. Wind gusts expected to increase after frontal passage but blended guidance indicates strongest 850mb jet will move in around Sunday evening. There will likely be a period of several hours in the evening with the strongest wind gusts, with blended guidance probability of greater than 30mph remaining high (around 60-80 percent).

Arctic air will rush into the area Sunday night with strong high pressure expected to move into the Mississippi Valley. While wind gusts will decrease overnight, forecast soundings indicate lingering elevated winds in the boundary layer which will contribute to bitter cold conditions. Blended guidance actually has fairly good agreement for lows Sunday night with the 25th to 75th percentile spread only about 3 degrees apart with high confidence of air temperatures in the teens. Maintaining the Extreme Cold Watch for Sunday night into Monday morning with the highest confidence in the need for either a warning or advisory in the counties highlighted in the watch with winds remaining higher in the eastern area lowering wind chills. LREF probabilities of minimum wind chills less than 15F remains high (60-80 percent) with probability of single digit wind chills generally between 20-40 percent favoring the northeastern portion of the area.

Cold will continue into Monday as high probability of temperatures remaining in the 30s through the day (60-80 percent). With high pressure ridging into the area, winds expected to decrease. As the high settles over the southeastern US, favorable radiational cooling is expected Monday night. Will need to watch guidance trends as blended guidance sometimes struggles in strong radiational cooling nights. Air temperatures expected to continue to be well below average, however, without significant wind, wind chills expected to remain above cold weather advisory criteria.

LONG TERM /TUESDAY THROUGH FRIDAY/

Key message(s):

- Temperatures moderate to above average by the end of the week.

Air mass will moderate beginning Tuesday and continuing through the end of the week. Ensemble means indicate weak ridging developing across the area. Moisture likely to increase towards the end of the week with a much weaker front approaching. This will lead to chances for showers but otherwise relatively benign weather expected through the long term period.

AVIATION /07Z SATURDAY THROUGH WEDNESDAY/

A cold front will move through the region near 12Z Sunday bringing gusty, NW winds and possibly a few showers. Otherwise no impacts expected.

SW flow strengthens today ahead of an approaching cold front. Winds will range from 5 to 10 kts from 15Z to 23Z. As the cold front approaches from the north and west after 06Z tonight, a few showers may develop. Coverage will be limited and any rain amounts will likely be very light so impacts to the terminals are unlikely. Once the front moves through on Sunday winds will shift to the NW and gusts will pick up.

EXTENDED AVIATION OUTLOOK...Widespread restrictions look unlikely after Sunday as a cold, dry air mass settles into the region.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Extreme Cold Watch from Sunday evening through Monday morning for SCZ027>031-035-037-038-041-135>137. GA...Extreme Cold Watch from Sunday evening through Monday morning for GAZ065-077.