Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 101807 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 207 PM EDT Sat Jun 10 2023 .SYNOPSIS...
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High pressure along with dry air will remain in control of the region through early tonight. Moisture will quickly return to the area tonight along with chances of showers and thunderstorms for Sunday through Monday, with a front passing on Monday night. A return to a more summertime pattern will begin early this week along with chances of mainly diurnal showers and storms Tuesday onward. There is the potential for a couple rounds of strong storms later this week, but there are details to iron out.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Seasonable temperatures this afternoon as dry air mass remains in place. A few cumulus clouds and high clouds advecting east. Deep upper low over the Canadian Maritimes with near zonal or west- northwest flow aloft across the Carolinas and Georgia. A relatively dry air mass remains in place at the moment with precipitable water around 0.7 inches. The ridge will be off shore this evening and overnight. This will result in an increasing south flow and resulting moisture advection into the area late tonight. Models suggest a warm front will move from southern Georgia this evening to near the Savannah River by daybreak. With some increasing clouds late tonight and warm air advection developing, temperatures tonight are expected to be about 10 degrees warmer than last night, lows in the mid 60s. Any showers should remain across central Ga through daybreak as moisture will be shallow.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Deep trough that will be the key to our weather in the long term is progged to begin digging into the Great Lakes on Sunday. This is the head of an unusually meridional & complex mid/upper level pattern across North America for this time of year, and the weather will behave as such. The trough will begin closing off in between the northern and southern streams of the jet stream on Sunday/Monday, deepening and meandering over the Great Lakes through 12z Tuesday. Southwest of this, a southern stream long wave trough will begin interacting with this closed low by Monday, with multiple shortwaves passing through the flow amidst increasingly strong westerlies. The first shortwave trough is progged to move through on Sunday, with a surface warm front preceding it across the southeastern US. This is forecast to replace a very dry airmass with a moisture rich one by midday Sunday, with showers and thunderstorms developing as a response to the approaching shortwave. There is some uncertainty regarding details, however. CAMs are all over the place regarding destabilization by early tomorrow afternoon, ranging from nothing across the area to ~1500 j/kg of MLCAPE depicted by the HRRR/RAP across the CSRA. The truth is likely somewhere in the middle, but it does look like there will be quite a gradient of CAPE across the region due to the presence of low dewpoints at 850 hPa. My expectation is that showers and storms develop across central GA and the CSRA by 16z-18z tomorrow and progress eastward throughout the day as the shortwave approaches. Strong, gusty winds are the primary threat from any stronger storm, but even DCAPE in forecast soundings looks <1000 j/kg. The soundings do look very moisture rich as the trough approaches, with skinny CAPE being the characterization of the profile across the CSRA. As such, heavy rain is almost a certainty with the storms, and any training could cause some localized flooding issues. Expecting a gradient in high temps from west to east given the earlier timing of showers and storms. Highs should range from the mid 80s west to near 90 in the east. Some showers/storms may redevelop overnight as showers and storms upstream push eastward. These are likely to weaken however, and I think we`ll have some subsidence behind the parent shortwave. Will still hold some PoPs overnight with this, and expecting lows to be in the mid and upper 60s. The parent shortwave will be pushing eastward by Monday morning, as timing on this has sped up quite a bit in recent runs. The GFS and Canadian have our forecast area well south of the best forcing by Monday afternoon, even as the surface front remains to our west. I`m growing increasingly skeptical of actually seeing much precip Monday afternoon, as CAMs are also painting a big ole MCS that dives towards the FL Panhandle and would rob us of big time moisture recovery. Will be bumping PoPs down on Monday afternoon as a result of all of this. Highs still should be in the mid and upper 80s, with lows in the mid 60s.
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&& .LONG TERM /TUESDAY THROUGH SATURDAY/...
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An active long term period could be on tap, with at least multiple days of storms possible. Additionally, a round or two of severe weather is not out of the question, either. Aforementioned closed low is shown by ensemble guidance to be slowly moving eastward across the Great Lakes by Tuesday morning. Much drier air is progged to be across the FA on Tuesday, with PWs below 1" across much of the area behind Monday`s frontal passage. Highs will be seasonal in the mid and upper 80s, with lows in the 60s. Front will begin to lift northward again as a pseudo warm/stationary front, and is progged to sit to our north again by Wednesday, with most guidance suggesting it will stay this way for several days to end the week. The placement of this boundary is key to our overall thunderstorm threat later this week. This will be critical, as there will be plenty of forcing through the end of the week. The closed low will slowly push into the northeast, while also not dragging a strong front through the area. So several shortwaves passing within anomalously strong westerly flow (U Wind at 500 hPa 90th+ Percentile from Wed-Fri) will certainly set us up from a shear perspective from strong storms, with forcing in place as well. The real question is where the front will set up during this period. South of the front, GEFS & CMC Ens are painting high probabilities (>60%) of >1000 j/kg of CAPE developing on these days. So the general ingredients are in place to favor multiple rounds of at least strong storms later this week, but the devil is in the details as always. I will note that the shear/CAPE combo is impressive for this time of year, so it bears close watching in the coming days. The CSU Machine Learning probabilities certainly paint the picture of a potential severe threat, honing in on Wednesday & Thursday specifically. Seasonal, summertime weather is likely to return next weekend with warm temps and more pulse convection as mid- level flow looks to weaken a good bit. In summary, the long term period looks potentially active, but there are definitely some details to iron out over the coming days.
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&& .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
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VFR conditions expected through at least 06z. Low clouds may develop near the AGS/DNL toward 12z but confidence low. Pressure ridge and relatively dry air mass over the region through this evening. The ridge will be moving off the coast and south-southeast low level flow will develop. This will result in an increase in low level moisture late tonight into Sunday morning. Some guidance suggests stratus may develop near the Savannah River toward morning but confidence is low on any restrictions. Included MVFR fog at AGS toward daybreak due to persistence and the increase in low-level moisture. High resolution models suggest some convection will develop over central GA late tonight and expected to move into the AGS/DNL terminal area during the morning. Winds will be variable/ or favor south this afternoon less than 10 knots. Light and variable winds overnight and south-southwest 5 to 10 knots Sunday. EXTENDED AVIATION OUTLOOK...Periodic restrictions are possible in afternoon convection Sunday associated with a warm front. A cold front will approach from the west late Monday and scattered thunderstorms expected ahead of the front. Diurnal showers and thunderstorms midweek may lead to brief restrictions.
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&& .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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