textproduct: Columbia

SYNOPSIS

Cool and mostly dry conditions are expected today, though a few showers are possible along and ahead of a cold front. A period of moderate to heavy rainfall is expected with the next storm system Monday night into Tuesday. High pressure then builds back in for Wednesday and Thursday before another system may take aim at the region to end the week.

NEAR TERM /THROUGH TONIGHT/

Key message(s):

- Moisture continues to increase. - Mainly cloudy and warmer with a few showers possible along and ahead of an approaching cold front. - Front moves through tonight.

Early this morning: Moisture will be slowly on the increase through the remainder of the night. All this will do is begin to bring surface dewpoints up through the 20s, while some low and mid level moisture brings some cloud cover across the region. These clouds will help to moderate morning low temperatures somewhat, with many areas only dropping into the upper 30s. Areas that see come clearing for periods though will drop into the lower 30s before rebounding with the return of clouds.

Today and Tonight: Another weak cold front will be approaching the region from the west throughout the daytime hours before pushing through tonight. Ahead of this front, pwat values will continue to slowly rise, topping out a little over an inch. Guidance is still showing some scattered light showers possible later this afternoon and into the early portions of the overnight. Blend generally gives the best chance for rainfall over the western counties late this afternoon, with mainly chance pops there. Rainfall chances slightly lower the further east you go as guidance shows the potential for some of the shower activity diminishing as it moves through the forecast area. As for temperatures, after a cool start to the day, afternoon highs will vary quite a bit from west to east. Western areas will see much more cloud over and blended guidance showing highs only in the lower 50s. Meanwhile further east highs climb to the middle 60s ahead of the front. Overnight lows will fall into the mid to upper 30s north and the lower to mid 40s in the Southern Midlands and CSRA.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Key message(s):

- Cool and dry Monday before rain chances increase quickly during the evening and especially overnight.

- Widespread moderate to heavy rain moves through the FA overnight Monday through Tuesday morning before diminishing.

Monday and Monday Night: Not much change in the outlook for Monday as high pressure remains north of the region, bringing cool northeasterly low level flow and aiding in developing in- situ wedge conditions. This should keep cloud cover much of the day and temperatures that remain in the low to mid 50s with northern spots toward the upper 40s. Mostly dry conditions are expected through the day as the the upper trough nears from the west with developing low pressure along the Gulf Coast. PWAT's remain near 1" much of the day but a general lack of forcing should bring mostly dry conditions until the evening and overnight with moisture rapidly increasing as the low and trough approach. Rain may move in from the west during the evening but forcing really ramps up overnight and into Tuesday morning with increasing isentropic lift and PVA from the trough, leading to widespread moderate to heavy rain into Tuesday morning.

Tuesday and Tuesday Night: At the start of the day, the surface low should be moving through the FA with the upper trough entering the region as well. Deep isentropic lift, a robust 50-60 kt LLJ, and PVA from the trough aid in bringing surging PWAT's upwards of 1.50-1.75" Tuesday morning. The combination of strong forcing should continue to yield widespread moderate to heavy rain across the FA before the low departs during the afternoon and rain chances taper off through the day from west to east. Confidence remains high in a fairly widespread 1"+ rainfall event where the EC Ensemble has multiple members showing spots toward 1.5-2". With the persistent dry conditions the region has seen, 6hr Flash Flood Guidance is generally over 3-4" thus Flash Flood concerns are low but some nuisance flooding cannot be ruled out with the efficient nature of this rainfall. As previously stated, forcing begins moving out during the afternoon and evening with diminishing rain chances before mostly clear skies are expected overnight. Temperatures should remain on the cool side, in the low to mid 50s, but some spots into the upper 50s could be seen depending when rain clears the area. Overnight lows should return toward the low to mid 30s.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Key message(s):

- High pressure brings cool and dry conditions Wednesday and Thursday.

- Another system may form in the Gulf, bringing back rain chances for the late week.

Solid agreement is seen for the midweek period as high pressure likely builds in behind Tuesday's system, bringing back cool and dry conditions Wednesday and Thursday. Temperatures likely remain below normal on Wednesday but may creep back close to normal on Thursday as southwesterly low level flow develops. To round out the week and start the weekend global models and ensemble guidance indicate another trough digs into the western US, bringing increasingly southwesterly flow aloft over the Southeast and increasing moisture. The deterministic ECMWF, GFS, and Canadian show a degree of surface low development in the western Gulf again Friday and Saturday, but noteworthy timing differences still exist in its progression toward the Northeast. In general, the pattern favors increased rain chances each day, with cool temperatures likely continuing.

AVIATION /06Z SUNDAY THROUGH THURSDAY/

Mixture of mvfr/vfr ceilings overnight, with mainly vfr conditions then expected after sunrise.

With moisture increasing overnight, satellite and surface obs showing a good amount of cloud cover overspreading the forecast area. Better low-level moisture has moved into the Savannah River area, bringing mvfr ceilings to ags/dnl. Those should remain the next few hours before a return to vfr stratus towards sunrise. All remaining sites will see stratus through the 24 hour forecast period, with ceilings expected to remain vfr, with some scattered bases below 3kft still possible. A cold front will be moving into the region late this evening and early tonight. Ahead of this front, scattered light showers are expected. Coverage may remain limited, and have just mentioned prob30 for light rain and low end vfr ceilings at all but ogb as the front moves in this evening. Winds will be mainly light through late morning before turning more out of the west around 5 knots later this afternoon/evening as the front pushes in.

EXTENDED AVIATION OUTLOOK...The next weather system early in the week will keep the potential for restrictions in rain Monday and Tuesday, with highest likelihood of rain on Tuesday. Additional restrictions possible late in the week.

CAE WATCHES/WARNINGS/ADVISORIES

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