Paul is absolutely right about the variability of snow conditions, not only in time but also over short distances (e. g. whether it’s in the sun or in the shade) which makes any forecasting only very approximate at best. The most reliable sources of information are the SAIS avalanche forecasts and blogs
https://www.sais.gov.uk/ which give a good idea of current conditions and how they may be affected over the coming day. However, forecasts can always be wrong and it is better to be over-equipped than under-equipped. While they only formally cover certain parts of the Highlands, one can often reasonably interpolate from the nearest ones.
Bogginess varies on much longer timescales: the main factors are the seasonal (usually worse in winter unless frozen) and rainfall amounts over the preceding weeks.
Stream levels rise and fall extremely quickly in response to rainfall: the amount of rain in the preceding 24-48 hours is by far the biggest influence, though in Spring, snowmelt can also be an important consideration. SEPA reports water levels for a number of sites across the country
https://www2.sepa.org.uk/WaterLevels/ - upland sites are of more use than big rivers, and beware of sites downstream of dams.