Structurally, the so-called "Rheinische Verlaufsform" is nearly equivalent to the English progressive.
The "gerade" is optional.
Contrary to the name, the Rheinische Verlaufsform is not dialectal; it is grammatical in standard High German (although stylistically dialectal; it is focused on western regions, including Switzerland and the Ruhr region, and is comparatively less typical of Austria and eastern Germany). The main difference between this form and the English progressive is that it is far from the preferred way to talk about such events. So it is perfectly grammatical to say
- Wir gehen zu der Party, wo die Leute gerade am tanzen sind.
But it is usually not the preferred way. The simple present is usually preferred, especially when using the respective adverbs, e.g.
- Wir gehen zu der Party, wo die Leute (gerade/im Moment/jetzt) tanzen.
Linguistic note: structurally, the exact status of the Rheinische Verlaufsform is an open research question. However, it has been argued before that it is indeed a present progressive.
Orthographic note: if the Verlaufsform is indeed a progressive, it should be spelled as in my examples. If it is not, but a regular construction, it should be spelled with the verbal element capitalized:
Contemporary speakers disagree on what spelling to use, likely at least in part because they also disagree on if the Verlaufsform actually is a progressive,
Historical note: according to an influential theory by Elisabeth Leiss, aspect used to be marked using case, e.g. often on the article, in Middle German, so that
would, with the object in the Genitive, correspond to imperfective aspect, in contrast to the perfective
Since the rich and flexible case selection system of Old and Middle German was lost in the emergence of New High German, the basic marker of aspect was also lost, without a clear structural way of marking aspect emerging yet.
Adverbial indication of aspect will usually be the best option if context alone is not sufficient.