When convective weather impacts the New York Metro airspace, traffic managers may employ several tactics to mitigate weather impacts and maintain manageable and efficient flow of traffic to and from the airports. These tactics, which include maneuvering individual flights through weather, merging and redirecting traffic flows to avoid storms, and rerouting traffic from blocked routes onto unimpacted or less-impacted routes, all affect the capacity of the affected airspace resources (departure fixes, routes, or gates). Furthermore, the location of the weather impacts can have a great influence on the amount of leeway that traffic managers have in applying these tactics. In New York, departure fixes, the gateways to en route airspace where departure traffic from several metroplex airports are merged onto en route airways, are particularly critical. When congestion (volume of traffic in excess of capacity) occurs near departure fixes as a result of weather impacts, traffic managers must resort to airborne holding or unplanned departure stops to quickly reduce traffic over the fix to manageable levels. Nonetheless, when convective weather impacts densely packed and busy metroplex airspaces, it is inevitable that traffic will need to use impacted departure fixes and routes to keep delays in check. For this reason, predictions of the weather-impacted capacity of critical airspace resources like departure fixes that are based in the reality of commonly used impact mitigation tactics, are needed to help traffic managers anticipate and avoid disruptive congestion at weather-impacted departure fixes. The Route Availability Planning Tool (RAPT) is a departure management decision support tool that has been used in the New York operations since 2003. It predicts the weather impact on departure fixes and routes based on departure times. RAPT assigns a departure status (RED, YELLOW, or GREEN) to individual departure routes based on the departure time, the predicted severity of the convective weather that will impact the route, the likelihood that a pilot will deviate to avoid the weather along the route, and the operational sensitivity to deviations in the departure airspace that the route traverses. These blockages assist traffic managers in prompt route reopening of routes closed by convective weather impacts, as well as providing situational awareness for impeding impacts on routes. RAPT also identifies the location of weather impacts along the departure route. This paper presents an analysis of observed fair weather and convective weather impacted throughput on New York departure fixes. RAPT departure status and impact location are used to characterize the severity of departure fix weather impacts, and weather-impacted fix capacity ranges are estimated as a function of RAPT impacts. The use of traffic flow merging is identified, and weather impacted capacity ranges for commonly used merged flows are also estimated.