textproduct: Columbia

SYNOPSIS

Low pressure will approach from the west with a warm front developing over/near the area tonight. Rain will become widespread across the area overnight and continue into Saturday as the low pressure system works across the area. Expect dry weather for Sunday through mid week with warming temperatures.

NEAR TERM /THROUGH TONIGHT/

Key message(s):

- Rain developing late this evening and especially overnight.

High pressure prevails north of the region, while low pressure shifts across the southern Plains this afternoon and evening. As the low continues east tonight, a warm front will develop over or just near the area.

High level cloudiness has spread over the area and will continue to thicken/lower as the day progresses. Despite the cloud cover, temperatures will warm above normal due to the southwesterly flow in place, with highs generally ranging from 60-65.

Ahead of the approaching low to the west, the blended guidance shows rain developing generally after midnight and spreading east through the overnight hours as isentropic lift and moisture increases. However, the latest 12Z HREF guidance shows at least some patchy/light rain arriving by mid-late evening, and given that models tend to have a slow bias for onset of precipitation in warm air advection patterns, this earlier trend may prove correct.

Rainfall totals through tonight according to the least HREF will range from 0.4 inches across far western portions of the forecast area to a few hundredths of an inch across eastern portions of the forecast area where rain will develop latest. A few heavier rain bands could develop, and probabilistic data shows some rainfall amounts upwards of 0.6 inches possible.

Temperatures tonight should be mild given the cloud cover and continued southerly/southwesterly flow, with lows 45-50 with a few lower 40s up in the Catawba and Pee Dee.

SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/

Key message(s):

- Widespread rain with isolated thunderstorms possible

- Daytime temperatures may be cooler than forecast

Showers should be ongoing early Saturday morning as a low pressure system tracks across the Southeast. A warm front should be draped across the southern forecast area, or just south, with overrunning leading to widespread shower activity over much of the FA. The strongest moisture advection appears to be in the morning with the highest rain rates from the mean HREF peaking between 12Z and 18Z. Rain amounts are still likely to range around 0.5 to 1 inch throughout the event with CAMs continuing to support the forecast of localized amounts around 1.5 inches. Convective activity should diminish in the afternoon as the low moves to our east but moisture should wrap around the low leading to more stratiform rain into the late afternoon, eventually drying out in the evening or overnight.

What has changed is that models are showing stronger surface high pressure moving into the Mid Atlantic States with stronger NW flow into the forecast area. This would allow the warm front to develop further to our south than previously expected. While total rainfall amounts may not waiver as much, the potential for isolated thunderstorms or some of those localized heavier amounts is less certain. Apart from elevated convection north of the warm front, the threat of surface based thunderstorms and any severe weather threat may be well south.

Temperatures will be largely dependent on the location that the warm front sets up. Confidence has increased that locations north of I-20 will remain under wedge conditions through the day. So we have lowered highs into the 40s for the northern FA. Highs are currently forecast for the CSRA in the mid to upper 50s but it is possible that we stay much cooler if the warm front never lifts north of these areas.

LONG TERM /SUNDAY THROUGH FRIDAY/

Key message(s):

- Warming temps through the week, low rain chances late week

Weak surface high pressure and ridging should keep conditions dry over the region into mid week. As the air mass moderates and SW flow strengthens we should see temperatures warm to above normal by mid-week. By late week, the spread in atmospheric moisture increases in global ensembles as ridging tends to break down and SW flow strengthens. This pattern in the extended typically supports at least a slight chance of rain into late week. Temperatures will also remain above normal.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

VFR conditions initially, then rain develops tonight with flight restrictions due to lowering ceilings/visibility likely by Saturday morning.

High clouds will continue to thicken/lower through this evening. Rain is expected to develop late this evening and increase in coverage overnight due to an approaching low pressure system to the west and associated warm front developing over/near the area later tonight. Guidance suggests VFR conditions prevailing through most of the overnight hours, with flight restrictions likely occurring late tonight/early Saturday morning after about 11Z. IFR or lower conditions will then be possible through the end of the forecast period mainly due to low ceilings, but visibilities could also be reduced in moderate showers at times.

Winds will generally be west-southwest through the evening, perhaps a little gusty at times this afternoon. Winds should then become light/variable overnight, and increase out of the east or southeast Saturday morning north of the warm front.

EXTENDED AVIATION OUTLOOK... Restrictions are likely to continue through Saturday night as a storm system moves through the region. No significant aviation impacts are currently expected during the Sunday to Tuesday period.

CAE WATCHES/WARNINGS/ADVISORIES

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