Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 011533 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 1033 AM EST Mon Mar 1 2021 .SYNOPSIS... Rain showers are expected today as a cold front crosses the region. The front will stall just south of the area tonight and early Tuesday then return northward as a significant rain maker late Tuesday into Wednesday. Cooler and drier weather is expected from Thursday through Sunday as high pressure settles over the region. && .NEAR TERM /THROUGH TONIGHT/... Line of showers and gusty winds continues to cross the area with the cold front currently moving into the Upstate. Wind gusts with the broken line of convection have been in the 30 to 40 mph range and have been brief in duration however wind gusts of 20 to 25 mph will continue through the afternoon hours. Rainfall amounts have been light with showers with most locations receiving less than one tenth of an inch. Scattered showers will continue through much of the afternoon with the cold front crossing the forecast area by late afternoon with cooler and drier air moving in behind the front. High temperatures have a large gradient again this afternoon ranging from the upper 60s in the western Midlands and northern CSRA to the upper 70s in the eastern Midlands and southern CSRA. Tonight: Cold advection will increase as high pressure begins ridging into the area with low level flow shifting to out of the north. With northerly winds remaining elevated overnight, temperatures will drop into the upper 30s in the north to mid 40s in the south. With the cold front stalled just south of the forecast area, moisture will begin to return late, but rain is expected to hold off until Tuesday. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Through Tuesday afternoon is expected to remain dry and below average as the high pressure ridge moves offshore. Due the upper level anticyclonic flow over the mountain west, by Tuesday night, a sharp shortwave will cross the region. While it is relatively low amplitude system, the upper level dynamics are quite impressive and there is high confidence across all guidance in a significant rain event. The split flow in the west will allow the shortwave to interact with an active southern jet as it moves towards the southeast, with deep vort advection being the primary forcing for precipitation, supplemented with a strong 850mb jet and associated warm advection. Confidence is fairly high in the timing of the precip as guidance is consistent with the onset around 0z Wednesday; the majority of the GEFS, SREF, and NBM members bring in the precipitation into the CSRA around this time from south to north. Ahead of the shortwave, strong southerly flow will jump PWATs to 1+ inches and over the 90th percentile climatologically across the southern half of the forecast area. Convectively driven precip is expected to remain limited with only some highly elevated weak instability. There is some uncertainty in the QPF totals however. Part of this uncertainty is the departing surface ridge and dry low levels that could help setup a weak in-situ wedge late in the evening and overnight Tuesday. Coupled with the strong upper level forcing to the south, isentropic lift enhanced by a weak wedge should help extend heavier precip into the northern midlands. However, there is quite a bit of uncertainty across all guidance for total precip. While the SREF and GEFS mean QPFs are both around 1.5 inches for the CSRA and central midlands, both show large spreads from 0.5 to 3.5 inches in their members with no discernible clustering; in fact the variance in their members has increased in the last few runs. The SREF means have backed off slightly throughout today, but again the large variance in members makes this trend hard to put much belief in. Given these trends and the expected setup, one to two inches of rain is expected with high confidence in the CSRA, with somewhat lower confidence north and east. Given the still fairly saturated soil, the WPC has the southern portion of the forecast area in a marginal risk for excessive rainfall from this system. There is good agreement amongst the SREFs and GEFS in ending the precip by Wednesday afternoon as some strong cold advection begins on the backside of the shortwave. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Behind the shortwave, a somewhat unique pattern will setup for the remainder of the forecast period with low confidence in any widespread rainfall beyond Wednesday. The active southern jet and a series of a retrograding systems in eastern Canada will help a deep upper level trough remain mostly stationary over the east coast of the US. The southeast should remain in northwest flow aloft with weak surface ridging. Across all ensemble guidance, heights and surface temperatures will stay at or below average from Thursday through Sunday. By the weekend, the NAEFS suggests below average temps at 850mb and 700mb as the trough deepens with another strong surge of the southern jet and a diving shortwave. The only potential weather maker of note is some cyclogenesis along the Florida coast that many of global ensembles members are showing. It appears that this development will all be well east of the region, given the position of the trough axis. By late in the weekend, the GEFS and EC ensemble both consistently show an anomalously strong surface ridge building into the region on the backside the deep upper trough. && .AVIATION /15Z MONDAY THROUGH FRIDAY/... VFR conditions through much of the period with TEMPO restrictions. Cold front continues moving toward the area with a line of showers currently crossing the terminals. Expect wind gusts around 35 knots with fropa. Scattered light showers will continue through afternoon however with the scattered nature have remained with VCSH. Winds through this evening will be northwesterly and breezy with gusts between 15 to 20kts. Winds will veer to northerly overnight and diminish to around 5kts during the early morning hours. EXTENDED AVIATION OUTLOOK...Restrictions likely Tuesday night and Wednesday as a low pressure system brings rain and clouds to the region. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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