Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 231022 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 622 AM EDT Mon May 23 2022 .SYNOPSIS... A weak tropical wave will push towards us through the day today. Abundant moisture combining with instability and weak upper disturbances moving into the region will keep the chance of showers and storms in the forecast through Tuesday. Another stronger upper trough and cold front will approach the region on Thursday into Friday bringing elevated chances of rain before drier air moves in over the weekend. && .NEAR TERM /THROUGH TONIGHT/... Clouds are plentiful, with some breaks, across the region currently as moisture streams into the region ahead of a tropical wave. Subjective analysis of 00z upper air obs revealed a general meridional pattern across the CONUS, with a large scale trough centered across the Rockies. East of that, a weak wave is emerging from the gulf, and is noted from the surface through 500 hPa. Surface analysis indicates a fairly strong high pressure system across the central US, with an open surface trough over the gulf. This will move towards today and bring with it active weather. Until then, we`ll see temps stay pretty close to where they are now for lows - mid 60s to low 70s across the area. Clouds will likely hang around through the night. As we get into the day today, active weather is expected to unfold. Widespread cloud cover is expected to start the day across the area as copious moisture will be around ahead of an approaching low from the Gulf of Mexico. Guidance begins the day with PWs in the 1.4-1.6" range across the region before a surge of moisture brings PWs in the 1.6-1.8" range to the region by 11a and 2p. This is ahead of the aforementioned mid-level trough and surface low pressure that will approach, providing plenty of forcing to work with in addition to the copious moisture. Big question today regards overall destabilization. Model guidance across the board has a line of heavy showers and thunderstorms pushing through at some point today along an area of convergence associated with the surface low/trough. The question is timing, which we don`t have a great handle on at this point. HREF CAM suite is spread fairly considerably, ranging from the HRRR which pushes convection in by 11a in the CSRA to the 3km NAM which doesn`t have convection in here until 3p or 4p at the earliest. Destabilization will likely be driven by moisture advection ahead of the low, as surface dewpoints are expect to approach 70F in the southern portion of the forecast area. Ultimately, there is a wide range of instability outcomes, dependent on when the storms push through. The later, the more we`ll be able to warm and destabilize, with values likely to end up in the 1000- 2000 j/kg range at best. Shear is not expected to be significant across the area, with 0-6km values of 25-30 knots across the area. This will likely be just sufficient enough to organize a multi-cell cluster of storms to push in during the late morning and afternoon hours across the region, with damaging winds the most likely threat. Even that could be tough to materialize, with a moisture rich and warm atmosphere. All in all, it seems the Marginal Risk for severe from SPC is justified, given that a cluster of thunderstorms is expected to quickly push through the region at some point today. Whether we get severe storms or not, heavy rainfall is expected with the storms given that PWs will be around 150% of normal, and we have solid forcing for ascent with this approaching system. Totals could actually be pretty high if storms are able to train; the HREF is showing the possibility of 1.5" or more in isolated spots. The environment certainly supports this, and I think that isolated flash flooding is possible. Right now, it do not look like we will see enough rain across the area to justify a Flash Flood Watch. Think highs will be in the low and mid 80s this afternoon, with some upper 80s in the far east where the rain reaches later. Overnight tonight, some convection will likely remain near or around the area through Midnight. Moisture will still be around, but the best forcing will be pushing northeastward pretty quickly. As a result, generally expecting showers and storms to diminish across the region after midnight, with a weak/diffuse boundary slowly pushing into our area and settling. Overnight lows will range from the low to upper 60s due to cloud cover and copious low-level moisture remaining. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... Tuesday and Tuesday night...Deep moisture will remain over the area. The ensembles suggest high probability of precipitable water > 1.50 inches. The GFS and Nam have values around 1.8 inches across the region. The frontal boundary should be in the northern Midlands early in the day but may shift south through the day. Instability possibly moderate south of the front. With ridge offshore...mid level short wave troughs rotating around ridge may act as a trigger for mainly diurnally driven scattered showers and thunderstorms. Temps tricky with front in the area but expect mainly 80s with upper 70s in the north Midlands north of the front. Lows in the 60s. Wednesday and Wednesday night...Diffuse frontal boundary should be still near the area perhaps in the south Midlands. Precipitable water may decrease a bit but remain relatively high for this time of year. Upper level forcing for convection may be more limited as upper ridge offshore builds a little to the west. Moderate instability still expected south of the frontal boundary. Will continue scattered mainly diurnally driven afternoon and evening showers and thunderstorms. Temps expected to be a little warmer than Tuesday with highs mainly in the 80s and lows in the 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The extended forecast period continues to be active through the end of the week as an upper trough in the Midwest moves slowly east. Southwest flow aloft will keep deep moisture over the region into Friday. With strong moisture advection Thursday and the upper trough pushing a strong cold front through the area Friday, expect numerous/widespread showers and thunderstorms Thursday into the overnight. Severe weather also possible. As the upper trough axis shifts east over the area on Friday, the deeper moisture shifts to the coast with drier air arriving from the west behind the front. Kept the lower pops over the weekend with drier air in place and some upper level ridging building in. Temperatures this period will generally be near normal. && .AVIATION /10Z MONDAY THROUGH FRIDAY/...
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VFR for now, with restrictions possible later today in convection. AGS hasn`t really seen any restrictions, so we managed to avoid vis and cig restrictions overnight. That likely won`t be the case today, as a weak tropical wave approaches from the west and brings with it widespread showers and thunderstorms late this morning and into the afternoon. Confident enough to add the TEMPO group back to the TAFs, but they are still rather large time periods as the models waffle back and forth on timing. VIS restrictions are definitely expected, as rain should be heavy, and some cig restrictions could occur as well. Expectation is that the initial line of storms will push towards AGS/DNL by 15z-16z and then impact CAE/CUB/OGB thereafter. There is some trending towards another round of storms later in the evening, and with copious moisture, I think it is a possibility. Keep VCSH to account for this and to not make the TAFs too lengthy. Winds should be fairly like through the day and out of the south and southwest. By tonight, convection should wind down and clouds remain. EXTENDED AVIATION OUTLOOK...Chance of mainly diurnal showers and thunderstorms and associated restrictions, along with a chance of mainly late night/morning fog and/or stratus, through the period.
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&& .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS... NEAR TERM... SHORT TERM... LONG TERM... AVIATION...

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