The Southerly could cause a surge of migrants but the level of cloud cover and precipitation will be a big influence on where and if things drop and concentrate. With such a deep southerly draw could be overshoots involved. The brisk south easterly on Sunday has got to be good for seawatching at Dungeness, surely Poms on the cards.
Raptors: The tail wind isn't always helpful to raptors but if its a light tail wind and a warm southerly airflow with clearish skies it could be interesting.
Passerine/landbird migrants: This really depends on cloud cover for dropping birds such as Wheatears, Yellow Wagtails, other chats and warblers. Even a chance of an overshoot such as Red-rumped Swallow with such a southerly airflow. Got to be good for Swallow and hirundine passage. Swifts are going to arrive in bigger numbers.
Waders: Peak time for waders now, just need a bit of cloud and preferably rain. The south easterly could push birds into the catchment. Could be interesting on the reservoirs.
Terns: That south easterly has got to be a guarantee for an influx of Little Gulls, Arctic Terns and other Terns especially on the reservoirs.
Waterfowl: Maybe Garganey still.
Gulls: Still not too late for a mega gull- the Glaucous-winged at Beddington was on April 17th and recently been a national mini-influx of Bonaparte's Gull and also an American Herring Gull in Suffolk.
Seabirds: The South-easterly could produce- spring skuas are gold inland but its a good time of year.